If you want to run V8 on your local machine, please use jsvu
- Ignition: V8 features an interpreter called
Ignition. Ignition is optimized to make code run as soon as possible.Ignitionconverts js code tobytecode - Liftoff: V8 has a streaming Wasm compiler called
Liftoffwhich, likeIgnition, is geared to get your code running quickly, at the cost of generating potentially suboptimal execution speed. - Sparkplug:
Sparkplugtakes Ignition’s output (the infamous “bytecode”) and turns it into non-optimized machine code, yielding better performance at the cost of increased memory footprint. - TurboFan: TurboFan is one of V8’s optimizing compilers leveraging a concept called “Sea of Nodes”. Once sufficient data has been collected,
TurboFankicks in and generates low-level machine code that is optimized for those types. This will give another significant speed boost. - TurboProp: The overall idea is to develop a cut-down version of
TurboFan’s pipeline that can generate not quite as efficient code, but do so faster.
v8 [options] [-e <string>] [--shell] [[--module|--web-snapshot] <file>...]
v8 script.js (execute a JavaScript file)
v8 module.mjs (execute a JavaScript module file)
v8 --module script.js (execute a file as a JavaScript module)
v8 -e "print(2+2)" (execute a string)
v8 --shell (run an interactive JavaScript shell (like browser console environment))The following syntax for options is accepted (both '-' and '--' are ok):
--flag (bool flags only)
--no-flag (bool flags only)
--flag=value (non-bool flags only, no spaces around '=')
--flag value (non-bool flags only)
-- (captures all remaining args in JavaScript)
Examples:
v8 --print-bytcode script.js (print bytecode generated by ignition interpreter)
v8 --no-harmony-shipping (disable all shipped harmony features)
--print-bytecode => print bytecode generated by ignition interpreter
--print-opt-source => print source code of optimized and inlined functions; useful for seeing what part of the code get optimized/inlined
--print-wasm-code => print WebAssembly code
--trace-opt => trace optimized compilation; know what part of the code get optimized using turbofan
--trace-deopt => trace deoptimization; know what part of the code get deoptimized with reason
--trace-baseline => trace baseline compilation; know what part of the code get compiled using sparkplug
--trace-turbo => trace generated TurboFan IR; know what part of the code get compiled using turboprop
--trace-wasm => trace wasm function calls
--trace-gc => print one trace line following each garbage collection
--turboprop => enable experimental turboprop mid-tier compiler
--turboprop-as-toptier => enable experimental turboprop compiler without further tierup to turbofan
--sparkplug => enable Sparkplug baseline compiler
--liftoff => enable Liftoff, the baseline compiler for WebAssembly
--liftoff-only => disallow TurboFan compilation for WebAssembly (for testing)
--lite-mode => enables trade-off of performance for memory savings
--optimize-for-size => enables optimizations which favor memory size over execution speed
--abort-on-contradictory-flags (Disallow flags or implications overriding each other.)
type: bool default: --abort-on-contradictory-flags
--allow-overwriting-for-next-flag (temporary disable flag contradiction to allow overwriting just the next flag)
type: bool default: --noallow-overwriting-for-next-flag
--use-strict (enforce strict mode)
type: bool default: --nouse-strict
--harmony (enable all completed harmony features)
type: bool default: --noharmony
--harmony-shipping (enable all shipped harmony features)
type: bool default: --harmony-shipping
--harmony-weak-refs-with-cleanup-some (enable "harmony weak references with FinalizationRegistry.prototype.cleanupSome" (in progress))
type: bool default: --noharmony-weak-refs-with-cleanup-some
--harmony-import-assertions (enable "harmony import assertions" (in progress))
type: bool default: --noharmony-import-assertions
--harmony-rab-gsab (enable "harmony ResizableArrayBuffer / GrowableSharedArrayBuffer" (in progress))
type: bool default: --noharmony-rab-gsab
--harmony-temporal (enable "Temporal" (in progress))
type: bool default: --noharmony-temporal
--harmony-intl-best-fit-matcher (enable "Intl BestFitMatcher")
type: bool default: --noharmony-intl-best-fit-matcher
--harmony-sharedarraybuffer (enable "harmony sharedarraybuffer")
type: bool default: --harmony-sharedarraybuffer
--harmony-atomics (enable "harmony atomics")
type: bool default: --harmony-atomics
--harmony-private-brand-checks (enable "harmony private brand checks")
type: bool default: --harmony-private-brand-checks
--harmony-relative-indexing-methods (enable "harmony relative indexing methods")
type: bool default: --harmony-relative-indexing-methods
--harmony-error-cause (enable "harmony error cause property")
type: bool default: --harmony-error-cause
--harmony-object-has-own (enable "harmony Object.hasOwn")
type: bool default: --harmony-object-has-own
--harmony-class-static-blocks (enable "harmony static initializer blocks")
type: bool default: --harmony-class-static-blocks
--harmony-array-find-last (enable "harmony array find last helpers")
type: bool default: --harmony-array-find-last
--harmony-intl-enumeration (enable "Intl Enumeration API")
type: bool default: --harmony-intl-enumeration
--harmony-intl-locale-info (enable "Intl Locale info")
type: bool default: --harmony-intl-locale-info
--builtin-subclassing (subclassing support in built-in methods)
type: bool default: --builtin-subclassing
--enable-sharedarraybuffer-per-context (enable the SharedArrayBuffer constructor per context)
type: bool default: --noenable-sharedarraybuffer-per-context
--icu-timezone-data (get information about timezones from ICU)
type: bool default: --icu-timezone-data
--stress-snapshot (disables sharing of the read-only heap for testing)
type: bool default: --nostress-snapshot
--lite-mode (enables trade-off of performance for memory savings)
type: bool default: --nolite-mode
--future (Implies all staged features that we want to ship in the not-too-far future)
type: bool default: --nofuture
--jitless (Disable runtime allocation of executable memory.)
type: bool default: --nojitless
--assert-types (generate runtime type assertions to test the typer)
type: bool default: --noassert-types
--trace-compilation-dependencies (trace code dependencies)
type: bool default: --notrace-compilation-dependencies
--allocation-site-pretenuring (pretenure with allocation sites)
type: bool default: --allocation-site-pretenuring
--page-promotion (promote pages based on utilization)
type: bool default: --page-promotion
--page-promotion-threshold (min percentage of live bytes on a page to enable fast evacuation)
type: int default: --page-promotion-threshold=70
--trace-pretenuring (trace pretenuring decisions of HAllocate instructions)
type: bool default: --notrace-pretenuring
--trace-pretenuring-statistics (trace allocation site pretenuring statistics)
type: bool default: --notrace-pretenuring-statistics
--track-field-types (track field types)
type: bool default: --track-field-types
--trace-block-coverage (trace collected block coverage information)
type: bool default: --notrace-block-coverage
--trace-protector-invalidation (trace protector cell invalidations)
type: bool default: --notrace-protector-invalidation
--trace-web-snapshot (trace web snapshot deserialization)
type: bool default: --notrace-web-snapshot
--feedback-normalization (feed back normalization to constructors)
type: bool default: --nofeedback-normalization
--unbox-double-arrays (automatically unbox arrays of doubles)
type: bool default: --unbox-double-arrays
--ticks-before-optimization (the number of times we have to go through the interrupt budget before considering this function for optimization)
type: int default: --ticks-before-optimization=3
--bytecode-size-allowance-per-tick (increases the number of ticks required for optimization by bytecode.length/X)
type: int default: --bytecode-size-allowance-per-tick=1100
--interrupt-budget (interrupt budget which should be used for the profiler counter)
type: int default: --interrupt-budget=135168
--max-bytecode-size-for-early-opt (Maximum bytecode length for a function to be optimized on the first tick)
type: int default: --max-bytecode-size-for-early-opt=81
--use-ic (use inline caching)
type: bool default: --use-ic
--budget-for-feedback-vector-allocation (The budget in amount of bytecode executed by a function before we decide to allocate feedback vectors)
type: int default: --budget-for-feedback-vector-allocation=940
--scale-factor-for-feedback-allocation (scale bytecode size for feedback vector allocation.)
type: int default: --scale-factor-for-feedback-allocation=8
--feedback-allocation-on-bytecode-size (Instead of a fixed budget for lazy feedback vector allocation, scale it based in the bytecode size.)
type: bool default: --feedback-allocation-on-bytecode-size
--lazy-feedback-allocation (Allocate feedback vectors lazily)
type: bool default: --lazy-feedback-allocation
--ignition-elide-noneffectful-bytecodes (elide bytecodes which won't have any external effect)
type: bool default: --ignition-elide-noneffectful-bytecodes
--ignition-reo (use ignition register equivalence optimizer)
type: bool default: --ignition-reo
--ignition-filter-expression-positions (filter expression positions before the bytecode pipeline)
type: bool default: --ignition-filter-expression-positions
--ignition-share-named-property-feedback (share feedback slots when loading the same named property from the same object)
type: bool default: --ignition-share-named-property-feedback
--print-bytecode (print bytecode generated by ignition interpreter)
type: bool default: --noprint-bytecode
--enable-lazy-source-positions (skip generating source positions during initial compile but regenerate when actually required)
type: bool default: --enable-lazy-source-positions
--stress-lazy-source-positions (collect lazy source positions immediately after lazy compile)
type: bool default: --nostress-lazy-source-positions
--print-bytecode-filter (filter for selecting which functions to print bytecode)
type: string default: --print-bytecode-filter="*"
--trace-ignition-codegen (trace the codegen of ignition interpreter bytecode handlers)
type: bool default: --notrace-ignition-codegen
--trace-ignition-dispatches-output-file (write the bytecode handler dispatch table to the specified file (d8 only) (requires building with v8_enable_ignition_dispatch_counting))
type: string default: --trace-ignition-dispatches-output-file=""
--trace-track-allocation-sites (trace the tracking of allocation sites)
type: bool default: --notrace-track-allocation-sites
--trace-migration (trace object migration)
type: bool default: --notrace-migration
--trace-generalization (trace map generalization)
type: bool default: --notrace-generalization
--turboprop (enable experimental turboprop mid-tier compiler)
type: bool default: --noturboprop
--turboprop-mid-tier-reg-alloc (enable mid-tier register allocator for turboprop)
type: bool default: --turboprop-mid-tier-reg-alloc
--turboprop-as-toptier (enable experimental turboprop compiler without further tierup to turbofan)
type: bool default: --noturboprop-as-toptier
--turboprop-inline-scaling-factor (scale factor for reduction in bytecode that can be inline for TurboProp compared to TurboFan)
type: int default: --turboprop-inline-scaling-factor=4
--interrupt-budget-scale-factor-for-top-tier (scale factor for profiler ticks when tiering up from midtier)
type: int default: --interrupt-budget-scale-factor-for-top-tier=20
--sparkplug (enable Sparkplug baseline compiler)
type: bool default: --sparkplug
--always-sparkplug (directly tier up to Sparkplug code)
type: bool default: --noalways-sparkplug
--baseline-batch-compilation (batch compile Sparkplug code)
type: bool default: --baseline-batch-compilation
--concurrent-sparkplug-max-threads (max number of threads that concurrent Sparkplug can use (0 for unbounded))
type: uint default: --concurrent-sparkplug-max-threads=0
--sparkplug-filter (filter for Sparkplug baseline compiler)
type: string default: --sparkplug-filter="*"
--sparkplug-needs-short-builtins (only enable Sparkplug baseline compiler when --short-builtin-calls are also enabled)
type: bool default: --nosparkplug-needs-short-builtins
--baseline-batch-compilation-threshold (the estimated instruction size of a batch to trigger compilation)
type: int default: --baseline-batch-compilation-threshold=4096
--trace-baseline (trace baseline compilation)
type: bool default: --notrace-baseline
--trace-baseline-batch-compilation (trace baseline batch compilation)
type: bool default: --notrace-baseline-batch-compilation
--trace-baseline-concurrent-compilation (trace baseline concurrent compilation)
type: bool default: --notrace-baseline-concurrent-compilation
--shared-string-table (internalize strings into shared table)
type: bool default: --noshared-string-table
--concurrent-recompilation (optimizing hot functions asynchronously on a separate thread)
type: bool default: --concurrent-recompilation
--trace-concurrent-recompilation (track concurrent recompilation)
type: bool default: --notrace-concurrent-recompilation
--concurrent-recompilation-queue-length (the length of the concurrent compilation queue)
type: int default: --concurrent-recompilation-queue-length=8
--concurrent-recompilation-delay (artificial compilation delay in ms)
type: int default: --concurrent-recompilation-delay=0
--concurrent-inlining (run optimizing compiler's inlining phase on a separate thread)
type: bool default: --concurrent-inlining
--stress-concurrent-inlining (create additional concurrent optimization jobs but throw away result)
type: bool default: --nostress-concurrent-inlining
--stress-concurrent-inlining-attach-code (create additional concurrent optimization jobs)
type: bool default: --nostress-concurrent-inlining-attach-code
--max-serializer-nesting (maximum levels for nesting child serializers)
type: int default: --max-serializer-nesting=25
--trace-heap-broker-verbose (trace the heap broker verbosely (all reports))
type: bool default: --notrace-heap-broker-verbose
--trace-heap-broker-memory (trace the heap broker memory (refs analysis and zone numbers))
type: bool default: --notrace-heap-broker-memory
--trace-heap-broker (trace the heap broker (reports on missing data only))
type: bool default: --notrace-heap-broker
--stress-runs (number of stress runs)
type: int default: --stress-runs=0
--deopt-every-n-times (deoptimize every n times a deopt point is passed)
type: int default: --deopt-every-n-times=0
--print-deopt-stress (print number of possible deopt points)
type: bool default: --noprint-deopt-stress
--opt (use adaptive optimizations)
type: bool default: --opt
--turbo-sp-frame-access (use stack pointer-relative access to frame wherever possible)
type: bool default: --noturbo-sp-frame-access
--stress-turbo-late-spilling (optimize placement of all spill instructions, not just loop-top phis)
type: bool default: --nostress-turbo-late-spilling
--turbo-filter (optimization filter for TurboFan compiler)
type: string default: --turbo-filter="*"
--trace-turbo (trace generated TurboFan IR)
type: bool default: --notrace-turbo
--trace-turbo-path (directory to dump generated TurboFan IR to)
type: string default: --trace-turbo-path=""
--trace-turbo-filter (filter for tracing turbofan compilation)
type: string default: --trace-turbo-filter="*"
--trace-turbo-graph (trace generated TurboFan graphs)
type: bool default: --notrace-turbo-graph
--trace-turbo-scheduled (trace TurboFan IR with schedule)
type: bool default: --notrace-turbo-scheduled
--trace-turbo-cfg-file (trace turbo cfg graph (for C1 visualizer) to a given file name)
type: string default: --trace-turbo-cfg-file=""
--trace-turbo-types (trace TurboFan's types)
type: bool default: --trace-turbo-types
--trace-turbo-scheduler (trace TurboFan's scheduler)
type: bool default: --notrace-turbo-scheduler
--trace-turbo-reduction (trace TurboFan's various reducers)
type: bool default: --notrace-turbo-reduction
--trace-turbo-trimming (trace TurboFan's graph trimmer)
type: bool default: --notrace-turbo-trimming
--trace-turbo-jt (trace TurboFan's jump threading)
type: bool default: --notrace-turbo-jt
--trace-turbo-ceq (trace TurboFan's control equivalence)
type: bool default: --notrace-turbo-ceq
--trace-turbo-loop (trace TurboFan's loop optimizations)
type: bool default: --notrace-turbo-loop
--trace-turbo-alloc (trace TurboFan's register allocator)
type: bool default: --notrace-turbo-alloc
--trace-all-uses (trace all use positions)
type: bool default: --notrace-all-uses
--trace-representation (trace representation types)
type: bool default: --notrace-representation
--trace-turbo-stack-accesses (trace stack load/store counters for optimized code in run-time (x64 only))
type: bool default: --notrace-turbo-stack-accesses
--turbo-verify (verify TurboFan graphs at each phase)
type: bool default: --noturbo-verify
--turbo-verify-machine-graph (verify TurboFan machine graph before instruction selection)
type: string default: --turbo-verify-machine-graph=""
--trace-verify-csa (trace code stubs verification)
type: bool default: --notrace-verify-csa
--csa-trap-on-node (trigger break point when a node with given id is created in given stub. The format is: StubName,NodeId)
type: string default: --csa-trap-on-node=""
--turbo-stats (print TurboFan statistics)
type: bool default: --noturbo-stats
--turbo-stats-nvp (print TurboFan statistics in machine-readable format)
type: bool default: --noturbo-stats-nvp
--turbo-stats-wasm (print TurboFan statistics of wasm compilations)
type: bool default: --noturbo-stats-wasm
--turbo-splitting (split nodes during scheduling in TurboFan)
type: bool default: --turbo-splitting
--function-context-specialization (enable function context specialization in TurboFan)
type: bool default: --nofunction-context-specialization
--turbo-inlining (enable inlining in TurboFan)
type: bool default: --turbo-inlining
--max-inlined-bytecode-size (maximum size of bytecode for a single inlining)
type: int default: --max-inlined-bytecode-size=460
--max-inlined-bytecode-size-cumulative (maximum cumulative size of bytecode considered for inlining)
type: int default: --max-inlined-bytecode-size-cumulative=920
--max-inlined-bytecode-size-absolute (maximum absolute size of bytecode considered for inlining)
type: int default: --max-inlined-bytecode-size-absolute=4600
--reserve-inline-budget-scale-factor (scale factor of bytecode size used to calculate the inlining budget)
type: float default: --reserve-inline-budget-scale-factor=1.2
--max-inlined-bytecode-size-small (maximum size of bytecode considered for small function inlining)
type: int default: --max-inlined-bytecode-size-small=27
--max-optimized-bytecode-size (maximum bytecode size to be considered for optimization; too high values may cause the compiler to hit (release) assertions)
type: int default: --max-optimized-bytecode-size=61440
--min-inlining-frequency (minimum frequency for inlining)
type: float default: --min-inlining-frequency=0.15
--polymorphic-inlining (polymorphic inlining)
type: bool default: --polymorphic-inlining
--stress-inline (set high thresholds for inlining to inline as much as possible)
type: bool default: --nostress-inline
--trace-turbo-inlining (trace TurboFan inlining)
type: bool default: --notrace-turbo-inlining
--turbo-inline-array-builtins (inline array builtins in TurboFan code)
type: bool default: --turbo-inline-array-builtins
--use-osr (use on-stack replacement)
type: bool default: --use-osr
--trace-osr (trace on-stack replacement)
type: bool default: --notrace-osr
--analyze-environment-liveness (analyze liveness of environment slots and zap dead values)
type: bool default: --analyze-environment-liveness
--trace-environment-liveness (trace liveness of local variable slots)
type: bool default: --notrace-environment-liveness
--turbo-load-elimination (enable load elimination in TurboFan)
type: bool default: --turbo-load-elimination
--trace-turbo-load-elimination (trace TurboFan load elimination)
type: bool default: --notrace-turbo-load-elimination
--turbo-profiling (enable basic block profiling in TurboFan)
type: bool default: --noturbo-profiling
--turbo-profiling-verbose (enable basic block profiling in TurboFan, and include each function's schedule and disassembly in the output)
type: bool default: --noturbo-profiling-verbose
--turbo-profiling-log-builtins (emit data about basic block usage in builtins to v8.log (requires that V8 was built with v8_enable_builtins_profiling=true))
type: bool default: --noturbo-profiling-log-builtins
--turbo-verify-allocation (verify register allocation in TurboFan)
type: bool default: --noturbo-verify-allocation
--turbo-move-optimization (optimize gap moves in TurboFan)
type: bool default: --turbo-move-optimization
--turbo-jt (enable jump threading in TurboFan)
type: bool default: --turbo-jt
--turbo-loop-peeling (TurboFan loop peeling)
type: bool default: --turbo-loop-peeling
--turbo-loop-variable (TurboFan loop variable optimization)
type: bool default: --turbo-loop-variable
--turbo-loop-rotation (TurboFan loop rotation)
type: bool default: --turbo-loop-rotation
--turbo-cf-optimization (optimize control flow in TurboFan)
type: bool default: --turbo-cf-optimization
--turbo-escape (enable escape analysis)
type: bool default: --turbo-escape
--turbo-allocation-folding (TurboFan allocation folding)
type: bool default: --turbo-allocation-folding
--turbo-instruction-scheduling (enable instruction scheduling in TurboFan)
type: bool default: --noturbo-instruction-scheduling
--turbo-stress-instruction-scheduling (randomly schedule instructions to stress dependency tracking)
type: bool default: --noturbo-stress-instruction-scheduling
--turbo-store-elimination (enable store-store elimination in TurboFan)
type: bool default: --turbo-store-elimination
--trace-store-elimination (trace store elimination)
type: bool default: --notrace-store-elimination
--turbo-rewrite-far-jumps (rewrite far to near jumps (ia32,x64))
type: bool default: --turbo-rewrite-far-jumps
--stress-gc-during-compilation (simulate GC/compiler thread race related to https://crbug.com/v8/8520)
type: bool default: --nostress-gc-during-compilation
--turbo-fast-api-calls (enable fast API calls from TurboFan)
type: bool default: --noturbo-fast-api-calls
--reuse-opt-code-count (don't discard optimized code for the specified number of deopts.)
type: int default: --reuse-opt-code-count=0
--turbo-dynamic-map-checks (use dynamic map checks when generating code for property accesses if all handlers in an IC are the same for turboprop)
type: bool default: --noturbo-dynamic-map-checks
--turbo-compress-translation-arrays (compress translation arrays (experimental))
type: bool default: --noturbo-compress-translation-arrays
--turbo-inline-js-wasm-calls (inline JS->Wasm calls)
type: bool default: --noturbo-inline-js-wasm-calls
--turbo-use-mid-tier-regalloc-for-huge-functions (fall back to the mid-tier register allocator for huge functions (experimental))
type: bool default: --noturbo-use-mid-tier-regalloc-for-huge-functions
--turbo-force-mid-tier-regalloc (always use the mid-tier register allocator (for testing))
type: bool default: --noturbo-force-mid-tier-regalloc
--turbo-optimize-apply (optimize Function.prototype.apply)
type: bool default: --turbo-optimize-apply
--turbo-collect-feedback-in-generic-lowering (enable experimental feedback collection in generic lowering.)
type: bool default: --turbo-collect-feedback-in-generic-lowering
--isolate-script-cache-ageing (enable ageing of the isolate script cache.)
type: bool default: --isolate-script-cache-ageing
--script-delay (busy wait [ms] on every Script::Run)
type: float default: --script-delay=0
--script-delay-once (busy wait [ms] on the first Script::Run)
type: float default: --script-delay-once=0
--script-delay-fraction (busy wait after each Script::Run by the given fraction of the run's duration)
type: float default: --script-delay-fraction=0
--optimize-for-size (Enables optimizations which favor memory size over execution speed)
type: bool default: --nooptimize-for-size
--wasm-generic-wrapper (allow use of the generic js-to-wasm wrapper instead of per-signature wrappers)
type: bool default: --wasm-generic-wrapper
--expose-wasm (expose wasm interface to JavaScript)
type: bool default: --expose-wasm
--wasm-num-compilation-tasks (maximum number of parallel compilation tasks for wasm)
type: int default: --wasm-num-compilation-tasks=128
--wasm-write-protect-code-memory (write protect code memory on the wasm native heap with mprotect)
type: bool default: --nowasm-write-protect-code-memory
--wasm-memory-protection-keys (protect wasm code memory with PKU if available, no protection without support; fallback to mprotect by adding --wasm-write-protect-code-memory)
type: bool default: --nowasm-memory-protection-keys
--wasm-async-compilation (enable actual asynchronous compilation for WebAssembly.compile)
type: bool default: --wasm-async-compilation
--wasm-test-streaming (use streaming compilation instead of async compilation for tests)
type: bool default: --nowasm-test-streaming
--wasm-max-mem-pages (maximum number of 64KiB memory pages per wasm memory)
type: uint default: --wasm-max-mem-pages=65536
--wasm-max-table-size (maximum table size of a wasm instance)
type: uint default: --wasm-max-table-size=10000000
--wasm-max-code-space (maximum committed code space for wasm (in MB))
type: uint default: --wasm-max-code-space=4095
--wasm-tier-up (enable tier up to the optimizing compiler (requires --liftoff to have an effect))
type: bool default: --wasm-tier-up
--wasm-dynamic-tiering (enable dynamic tier up to the optimizing compiler)
type: bool default: --nowasm-dynamic-tiering
--wasm-tiering-budget (budget for dynamic tiering (rough approximation of bytes executed)
type: int default: --wasm-tiering-budget=1800000
--wasm-caching-threshold (the amount of wasm top tier code that triggers the next caching event)
type: int default: --wasm-caching-threshold=1000000
--trace-wasm-compilation-times (print how long it took to compile each wasm function)
type: bool default: --notrace-wasm-compilation-times
--wasm-tier-up-filter (only tier-up function with this index)
type: int default: --wasm-tier-up-filter=-1
--liftoff (enable Liftoff, the baseline compiler for WebAssembly)
type: bool default: --liftoff
--liftoff-only (disallow TurboFan compilation for WebAssembly (for testing))
type: bool default: --noliftoff-only
--trace-wasm-memory (print all memory updates performed in wasm code)
type: bool default: --notrace-wasm-memory
--wasm-tier-mask-for-testing (bitmask of functions to compile with TurboFan instead of Liftoff)
type: int default: --wasm-tier-mask-for-testing=0
--wasm-debug-mask-for-testing (bitmask of functions to compile for debugging, only applies if the tier is Liftoff)
type: int default: --wasm-debug-mask-for-testing=0
--validate-asm (validate asm.js modules before compiling)
type: bool default: --validate-asm
--suppress-asm-messages (don't emit asm.js related messages (for golden file testing))
type: bool default: --nosuppress-asm-messages
--trace-asm-time (print asm.js timing info to the console)
type: bool default: --notrace-asm-time
--trace-asm-scanner (print tokens encountered by asm.js scanner)
type: bool default: --notrace-asm-scanner
--trace-asm-parser (verbose logging of asm.js parse failures)
type: bool default: --notrace-asm-parser
--stress-validate-asm (try to validate everything as asm.js)
type: bool default: --nostress-validate-asm
--dump-wasm-module-path (directory to dump wasm modules to)
type: string default: --dump-wasm-module-path=""
--experimental-wasm-compilation-hints (enable prototype compilation hints section for wasm)
type: bool default: --noexperimental-wasm-compilation-hints
--experimental-wasm-gc (enable prototype garbage collection for wasm)
type: bool default: --noexperimental-wasm-gc
--experimental-wasm-nn-locals (enable prototype allow non-defaultable/non-nullable locals, validated with 'until end of block' semantics for wasm)
type: bool default: --noexperimental-wasm-nn-locals
--experimental-wasm-unsafe-nn-locals (enable prototype allow non-defaultable/non-nullable locals, no validation for wasm)
type: bool default: --noexperimental-wasm-unsafe-nn-locals
--experimental-wasm-assume-ref-cast-succeeds (enable prototype assume ref.cast always succeeds and skip the related type check (unsafe) for wasm)
type: bool default: --noexperimental-wasm-assume-ref-cast-succeeds
--experimental-wasm-skip-null-checks (enable prototype skip null checks for call.ref and array and struct operations (unsafe) for wasm)
type: bool default: --noexperimental-wasm-skip-null-checks
--experimental-wasm-skip-bounds-checks (enable prototype skip array bounds checks (unsafe) for wasm)
type: bool default: --noexperimental-wasm-skip-bounds-checks
--experimental-wasm-typed-funcref (enable prototype typed function references for wasm)
type: bool default: --noexperimental-wasm-typed-funcref
--experimental-wasm-memory64 (enable prototype memory64 for wasm)
type: bool default: --noexperimental-wasm-memory64
--experimental-wasm-relaxed-simd (enable prototype relaxed simd for wasm)
type: bool default: --noexperimental-wasm-relaxed-simd
--experimental-wasm-branch-hinting (enable prototype branch hinting for wasm)
type: bool default: --noexperimental-wasm-branch-hinting
--experimental-wasm-stack-switching (enable prototype stack switching for wasm)
type: bool default: --noexperimental-wasm-stack-switching
--experimental-wasm-return-call (enable prototype return call opcodes for wasm)
type: bool default: --noexperimental-wasm-return-call
--experimental-wasm-type-reflection (enable prototype wasm type reflection in JS for wasm)
type: bool default: --noexperimental-wasm-type-reflection
--experimental-wasm-simd (enable prototype SIMD opcodes for wasm)
type: bool default: --experimental-wasm-simd
--experimental-wasm-threads (enable prototype thread opcodes for wasm)
type: bool default: --experimental-wasm-threads
--experimental-wasm-eh (enable prototype exception handling opcodes for wasm)
type: bool default: --experimental-wasm-eh
--wasm-gc-js-interop (experimental WasmGC-JS interop)
type: bool default: --nowasm-gc-js-interop
--wasm-staging (enable staged wasm features)
type: bool default: --nowasm-staging
--wasm-opt (enable wasm optimization)
type: bool default: --wasm-opt
--wasm-bounds-checks (enable bounds checks (disable for performance testing only))
type: bool default: --wasm-bounds-checks
--wasm-stack-checks (enable stack checks (disable for performance testing only))
type: bool default: --wasm-stack-checks
--wasm-enforce-bounds-checks (enforce explicit bounds check even if the trap handler is available)
type: bool default: --nowasm-enforce-bounds-checks
--wasm-math-intrinsics (intrinsify some Math imports into wasm)
type: bool default: --wasm-math-intrinsics
--wasm-inlining (enable inlining of wasm functions into wasm functions (experimental))
type: bool default: --nowasm-inlining
--wasm-inlining-budget-factor (maximum allowed size to inline a function is given by {n / caller size})
type: size_t default: --wasm-inlining-budget-factor=75000
--wasm-inlining-max-size (maximum size of a function that can be inlined, in TF nodes)
type: size_t default: --wasm-inlining-max-size=1000
--wasm-speculative-inlining (enable speculative inlining of call_ref targets (experimental))
type: bool default: --nowasm-speculative-inlining
--trace-wasm-inlining (trace wasm inlining)
type: bool default: --notrace-wasm-inlining
--trace-wasm-speculative-inlining (trace wasm speculative inlining)
type: bool default: --notrace-wasm-speculative-inlining
--wasm-loop-unrolling (enable loop unrolling for wasm functions)
type: bool default: --wasm-loop-unrolling
--wasm-fuzzer-gen-test (generate a test case when running a wasm fuzzer)
type: bool default: --nowasm-fuzzer-gen-test
--print-wasm-code (print WebAssembly code)
type: bool default: --noprint-wasm-code
--print-wasm-code-function-index (print WebAssembly code for function at index)
type: int default: --print-wasm-code-function-index=-1
--print-wasm-stub-code (print WebAssembly stub code)
type: bool default: --noprint-wasm-stub-code
--asm-wasm-lazy-compilation (enable lazy compilation for asm-wasm modules)
type: bool default: --noasm-wasm-lazy-compilation
--wasm-lazy-compilation (enable lazy compilation for all wasm modules)
type: bool default: --nowasm-lazy-compilation
--wasm-lazy-validation (enable lazy validation for lazily compiled wasm functions)
type: bool default: --nowasm-lazy-validation
--wasm-simd-ssse3-codegen (allow wasm SIMD SSSE3 codegen)
type: bool default: --nowasm-simd-ssse3-codegen
--wasm-code-gc (enable garbage collection of wasm code)
type: bool default: --wasm-code-gc
--trace-wasm-code-gc (trace garbage collection of wasm code)
type: bool default: --notrace-wasm-code-gc
--stress-wasm-code-gc (stress test garbage collection of wasm code)
type: bool default: --nostress-wasm-code-gc
--wasm-max-initial-code-space-reservation (maximum size of the initial wasm code space reservation (in MB))
type: int default: --wasm-max-initial-code-space-reservation=0
--experimental-wasm-allow-huge-modules (allow wasm modules bigger than 1GB, but below ~2GB)
type: bool default: --noexperimental-wasm-allow-huge-modules
--trace-wasm (trace wasm function calls)
type: bool default: --notrace-wasm
--stress-sampling-allocation-profiler (Enables sampling allocation profiler with X as a sample interval)
type: int default: --stress-sampling-allocation-profiler=0
--lazy-new-space-shrinking (Enables the lazy new space shrinking strategy)
type: bool default: --nolazy-new-space-shrinking
--min-semi-space-size (min size of a semi-space (in MBytes), the new space consists of two semi-spaces)
type: size_t default: --min-semi-space-size=0
--max-semi-space-size (max size of a semi-space (in MBytes), the new space consists of two semi-spaces)
type: size_t default: --max-semi-space-size=0
--semi-space-growth-factor (factor by which to grow the new space)
type: int default: --semi-space-growth-factor=2
--max-old-space-size (max size of the old space (in Mbytes))
type: size_t default: --max-old-space-size=0
--max-heap-size (max size of the heap (in Mbytes) both max_semi_space_size and max_old_space_size take precedence. All three flags cannot be specified at the same time.)
type: size_t default: --max-heap-size=0
--initial-heap-size (initial size of the heap (in Mbytes))
type: size_t default: --initial-heap-size=0
--huge-max-old-generation-size (Increase max size of the old space to 4 GB for x64 systems withthe physical memory bigger than 16 GB)
type: bool default: --huge-max-old-generation-size
--initial-old-space-size (initial old space size (in Mbytes))
type: size_t default: --initial-old-space-size=0
--global-gc-scheduling (enable GC scheduling based on global memory)
type: bool default: --global-gc-scheduling
--gc-global (always perform global GCs)
type: bool default: --nogc-global
--random-gc-interval (Collect garbage after random(0, X) allocations. It overrides gc_interval.)
type: int default: --random-gc-interval=0
--gc-interval (garbage collect after <n> allocations)
type: int default: --gc-interval=-1
--retain-maps-for-n-gc (keeps maps alive for <n> old space garbage collections)
type: int default: --retain-maps-for-n-gc=2
--trace-gc (print one trace line following each garbage collection)
type: bool default: --notrace-gc
--trace-gc-nvp (print one detailed trace line in name=value format after each garbage collection)
type: bool default: --notrace-gc-nvp
--trace-gc-ignore-scavenger (do not print trace line after scavenger collection)
type: bool default: --notrace-gc-ignore-scavenger
--trace-idle-notification (print one trace line following each idle notification)
type: bool default: --notrace-idle-notification
--trace-idle-notification-verbose (prints the heap state used by the idle notification)
type: bool default: --notrace-idle-notification-verbose
--trace-gc-verbose (print more details following each garbage collection)
type: bool default: --notrace-gc-verbose
--trace-gc-freelists (prints details of each freelist before and after each major garbage collection)
type: bool default: --notrace-gc-freelists
--trace-gc-freelists-verbose (prints details of freelists of each page before and after each major garbage collection)
type: bool default: --notrace-gc-freelists-verbose
--trace-gc-heap-layout (print layout of pages in heap before and after gc)
type: bool default: --notrace-gc-heap-layout
--trace-gc-heap-layout-ignore-minor-gc (do not print trace line before and after minor-gc)
type: bool default: --trace-gc-heap-layout-ignore-minor-gc
--trace-evacuation-candidates (Show statistics about the pages evacuation by the compaction)
type: bool default: --notrace-evacuation-candidates
--trace-allocations-origins (Show statistics about the origins of allocations. Combine with --no-inline-new to track allocations from generated code)
type: bool default: --notrace-allocations-origins
--trace-pending-allocations (trace calls to Heap::IsAllocationPending that return true)
type: bool default: --notrace-pending-allocations
--trace-allocation-stack-interval (print stack trace after <n> free-list allocations)
type: int default: --trace-allocation-stack-interval=-1
--trace-duplicate-threshold-kb (print duplicate objects in the heap if their size is more than given threshold)
type: int default: --trace-duplicate-threshold-kb=0
--trace-fragmentation (report fragmentation for old space)
type: bool default: --notrace-fragmentation
--trace-fragmentation-verbose (report fragmentation for old space (detailed))
type: bool default: --notrace-fragmentation-verbose
--minor-mc-trace-fragmentation (trace fragmentation after marking)
type: bool default: --nominor-mc-trace-fragmentation
--trace-evacuation (report evacuation statistics)
type: bool default: --notrace-evacuation
--trace-mutator-utilization (print mutator utilization, allocation speed, gc speed)
type: bool default: --notrace-mutator-utilization
--incremental-marking (use incremental marking)
type: bool default: --incremental-marking
--incremental-marking-wrappers (use incremental marking for marking wrappers)
type: bool default: --incremental-marking-wrappers
--incremental-marking-task (use tasks for incremental marking)
type: bool default: --incremental-marking-task
--incremental-marking-soft-trigger (threshold for starting incremental marking via a task in percent of available space: limit - size)
type: int default: --incremental-marking-soft-trigger=0
--incremental-marking-hard-trigger (threshold for starting incremental marking immediately in percent of available space: limit - size)
type: int default: --incremental-marking-hard-trigger=0
--trace-unmapper (Trace the unmapping)
type: bool default: --notrace-unmapper
--parallel-scavenge (parallel scavenge)
type: bool default: --parallel-scavenge
--scavenge-task (schedule scavenge tasks)
type: bool default: --scavenge-task
--scavenge-task-trigger (scavenge task trigger in percent of the current heap limit)
type: int default: --scavenge-task-trigger=80
--scavenge-separate-stack-scanning (use a separate phase for stack scanning in scavenge)
type: bool default: --noscavenge-separate-stack-scanning
--trace-parallel-scavenge (trace parallel scavenge)
type: bool default: --notrace-parallel-scavenge
--concurrent-marking (use concurrent marking)
type: bool default: --concurrent-marking
--concurrent-array-buffer-sweeping (concurrently sweep array buffers)
type: bool default: --concurrent-array-buffer-sweeping
--stress-concurrent-allocation (start background threads that allocate memory)
type: bool default: --nostress-concurrent-allocation
--parallel-marking (use parallel marking in atomic pause)
type: bool default: --parallel-marking
--ephemeron-fixpoint-iterations (number of fixpoint iterations it takes to switch to linear ephemeron algorithm)
type: int default: --ephemeron-fixpoint-iterations=10
--trace-concurrent-marking (trace concurrent marking)
type: bool default: --notrace-concurrent-marking
--concurrent-sweeping (use concurrent sweeping)
type: bool default: --concurrent-sweeping
--parallel-compaction (use parallel compaction)
type: bool default: --parallel-compaction
--parallel-pointer-update (use parallel pointer update during compaction)
type: bool default: --parallel-pointer-update
--detect-ineffective-gcs-near-heap-limit (trigger out-of-memory failure to avoid GC storm near heap limit)
type: bool default: --detect-ineffective-gcs-near-heap-limit
--trace-incremental-marking (trace progress of the incremental marking)
type: bool default: --notrace-incremental-marking
--trace-stress-marking (trace stress marking progress)
type: bool default: --notrace-stress-marking
--trace-stress-scavenge (trace stress scavenge progress)
type: bool default: --notrace-stress-scavenge
--track-gc-object-stats (track object counts and memory usage)
type: bool default: --notrack-gc-object-stats
--trace-gc-object-stats (trace object counts and memory usage)
type: bool default: --notrace-gc-object-stats
--trace-zone-stats (trace zone memory usage)
type: bool default: --notrace-zone-stats
--zone-stats-tolerance (report a tick only when allocated zone memory changes by this amount)
type: size_t default: --zone-stats-tolerance=1048576
--trace-zone-type-stats (trace per-type zone memory usage)
type: bool default: --notrace-zone-type-stats
--track-retaining-path (enable support for tracking retaining path)
type: bool default: --notrack-retaining-path
--gc-stats (Used by tracing internally to enable gc statistics)
type: int default: --gc-stats=0
--track-detached-contexts (track native contexts that are expected to be garbage collected)
type: bool default: --track-detached-contexts
--trace-detached-contexts (trace native contexts that are expected to be garbage collected)
type: bool default: --notrace-detached-contexts
--move-object-start (enable moving of object starts)
type: bool default: --move-object-start
--memory-reducer (use memory reducer)
type: bool default: --memory-reducer
--memory-reducer-for-small-heaps (use memory reducer for small heaps)
type: bool default: --memory-reducer-for-small-heaps
--heap-growing-percent (specifies heap growing factor as (1 + heap_growing_percent/100))
type: int default: --heap-growing-percent=0
--v8-os-page-size (override OS page size (in KBytes))
type: int default: --v8-os-page-size=0
--allocation-buffer-parking (allocation buffer parking)
type: bool default: --allocation-buffer-parking
--compact (Perform compaction on full GCs based on V8's default heuristics)
type: bool default: --compact
--compact-code-space (Perform code space compaction on full collections.)
type: bool default: --compact-code-space
--compact-on-every-full-gc (Perform compaction on every full GC)
type: bool default: --nocompact-on-every-full-gc
--compact-with-stack (Perform compaction when finalizing a full GC with stack)
type: bool default: --compact-with-stack
--compact-code-space-with-stack (Perform code space compaction when finalizing a full GC with stack)
type: bool default: --compact-code-space-with-stack
--stress-compaction (Stress GC compaction to flush out bugs (implies --force_marking_deque_overflows))
type: bool default: --nostress-compaction
--stress-compaction-random (Stress GC compaction by selecting random percent of pages as evacuation candidates. Overrides stress_compaction.)
type: bool default: --nostress-compaction-random
--flush-baseline-code (flush of baseline code when it has not been executed recently)
type: bool default: --noflush-baseline-code
--flush-bytecode (flush of bytecode when it has not been executed recently)
type: bool default: --flush-bytecode
--stress-flush-code (stress code flushing)
type: bool default: --nostress-flush-code
--trace-flush-bytecode (trace bytecode flushing)
type: bool default: --notrace-flush-bytecode
--use-marking-progress-bar (Use a progress bar to scan large objects in increments when incremental marking is active.)
type: bool default: --use-marking-progress-bar
--stress-per-context-marking-worklist (Use per-context worklist for marking)
type: bool default: --nostress-per-context-marking-worklist
--force-marking-deque-overflows (force overflows of marking deque by reducing it's size to 64 words)
type: bool default: --noforce-marking-deque-overflows
--stress-incremental-marking (force incremental marking for small heaps and run it more often)
type: bool default: --nostress-incremental-marking
--fuzzer-gc-analysis (prints number of allocations and enables analysis mode for gc fuzz testing, e.g. --stress-marking, --stress-scavenge)
type: bool default: --nofuzzer-gc-analysis
--stress-marking (force marking at random points between 0 and X (inclusive) percent of the regular marking start limit)
type: int default: --stress-marking=0
--stress-scavenge (force scavenge at random points between 0 and X (inclusive) percent of the new space capacity)
type: int default: --stress-scavenge=0
--reclaim-unmodified-wrappers (reclaim otherwise unreachable unmodified wrapper objects when possible)
type: bool default: --reclaim-unmodified-wrappers
--gc-experiment-less-compaction (less compaction in non-memory reducing mode)
type: bool default: --nogc-experiment-less-compaction
--disable-abortjs (disables AbortJS runtime function)
type: bool default: --nodisable-abortjs
--randomize-all-allocations (randomize virtual memory reservations by ignoring any hints passed when allocating pages)
type: bool default: --norandomize-all-allocations
--manual-evacuation-candidates-selection (Test mode only flag. It allows an unit test to select evacuation candidates pages (requires --stress_compaction).)
type: bool default: --nomanual-evacuation-candidates-selection
--fast-promotion-new-space (fast promote new space on high survival rates)
type: bool default: --nofast-promotion-new-space
--clear-free-memory (initialize free memory with 0)
type: bool default: --noclear-free-memory
--crash-on-aborted-evacuation (crash when evacuation of page fails)
type: bool default: --nocrash-on-aborted-evacuation
--enable-sse3 (enable use of SSE3 instructions if available)
type: bool default: --enable-sse3
--enable-ssse3 (enable use of SSSE3 instructions if available)
type: bool default: --enable-ssse3
--enable-sse4-1 (enable use of SSE4.1 instructions if available)
type: bool default: --enable-sse4-1
--enable-sse4-2 (enable use of SSE4.2 instructions if available)
type: bool default: --enable-sse4-2
--enable-sahf (enable use of SAHF instruction if available (X64 only))
type: bool default: --enable-sahf
--enable-avx (enable use of AVX instructions if available)
type: bool default: --enable-avx
--enable-avx2 (enable use of AVX2 instructions if available)
type: bool default: --enable-avx2
--enable-fma3 (enable use of FMA3 instructions if available)
type: bool default: --enable-fma3
--enable-bmi1 (enable use of BMI1 instructions if available)
type: bool default: --enable-bmi1
--enable-bmi2 (enable use of BMI2 instructions if available)
type: bool default: --enable-bmi2
--enable-lzcnt (enable use of LZCNT instruction if available)
type: bool default: --enable-lzcnt
--enable-popcnt (enable use of POPCNT instruction if available)
type: bool default: --enable-popcnt
--arm-arch (generate instructions for the selected ARM architecture if available: armv6, armv7, armv7+sudiv or armv8)
type: string default: --arm-arch="armv8"
--force-long-branches (force all emitted branches to be in long mode (MIPS/PPC only))
type: bool default: --noforce-long-branches
--mcpu (enable optimization for specific cpu)
type: string default: --mcpu="auto"
--partial-constant-pool (enable use of partial constant pools (X64 only))
type: bool default: --partial-constant-pool
--sim-arm64-optional-features (enable optional features on the simulator for testing: none or all)
type: string default: --sim-arm64-optional-features="none"
--enable-source-at-csa-bind (Include source information in the binary at CSA bind locations.)
type: bool default: --noenable-source-at-csa-bind
--enable-armv7 (deprecated (use --arm_arch instead))
type: maybe_bool default: --enable-armv7=unset
--enable-vfp3 (deprecated (use --arm_arch instead))
type: maybe_bool default: --enable-vfp3=unset
--enable-32dregs (deprecated (use --arm_arch instead))
type: maybe_bool default: --enable-32dregs=unset
--enable-neon (deprecated (use --arm_arch instead))
type: maybe_bool default: --enable-neon=unset
--enable-sudiv (deprecated (use --arm_arch instead))
type: maybe_bool default: --enable-sudiv=unset
--enable-armv8 (deprecated (use --arm_arch instead))
type: maybe_bool default: --enable-armv8=unset
--enable-regexp-unaligned-accesses (enable unaligned accesses for the regexp engine)
type: bool default: --enable-regexp-unaligned-accesses
--script-streaming (enable parsing on background)
type: bool default: --script-streaming
--stress-background-compile (stress test parsing on background)
type: bool default: --nostress-background-compile
--concurrent-cache-deserialization (enable deserializing code caches on background)
type: bool default: --concurrent-cache-deserialization
--disable-old-api-accessors (Disable old-style API accessors whose setters trigger through the prototype chain)
type: bool default: --nodisable-old-api-accessors
--embedder-instance-types (enable type checks based on instance types provided by the embedder)
type: bool default: --noembedder-instance-types
--expose-gc (expose gc extension)
type: bool default: --noexpose-gc
--expose-gc-as (expose gc extension under the specified name)
type: string default: --expose-gc-as=""
--expose-externalize-string (expose externalize string extension)
type: bool default: --noexpose-externalize-string
--expose-trigger-failure (expose trigger-failure extension)
type: bool default: --noexpose-trigger-failure
--expose-ignition-statistics (expose ignition-statistics extension (requires building with v8_enable_ignition_dispatch_counting))
type: bool default: --noexpose-ignition-statistics
--stack-trace-limit (number of stack frames to capture)
type: int default: --stack-trace-limit=10
--builtins-in-stack-traces (show built-in functions in stack traces)
type: bool default: --nobuiltins-in-stack-traces
--experimental-stack-trace-frames (enable experimental frames (API/Builtins) and stack trace layout)
type: bool default: --noexperimental-stack-trace-frames
--disallow-code-generation-from-strings (disallow eval and friends)
type: bool default: --nodisallow-code-generation-from-strings
--expose-async-hooks (expose async_hooks object)
type: bool default: --noexpose-async-hooks
--expose-cputracemark-as (expose cputracemark extension under the specified name)
type: string default: --expose-cputracemark-as=""
--allow-unsafe-function-constructor (allow invoking the function constructor without security checks)
type: bool default: --noallow-unsafe-function-constructor
--force-slow-path (always take the slow path for builtins)
type: bool default: --noforce-slow-path
--test-small-max-function-context-stub-size (enable testing the function context size overflow path by making the maximum size smaller)
type: bool default: --notest-small-max-function-context-stub-size
--inline-new (use fast inline allocation)
type: bool default: --inline-new
--switch-table-spread-threshold (allow the jump table used for switch statements to span a range of integers roughly equal to this number times the number of clauses in the switch)
type: int default: --switch-table-spread-threshold=3
--switch-table-min-cases (the number of Smi integer cases present in the switch statement before using the jump table optimization)
type: int default: --switch-table-min-cases=6
--trace (trace javascript function calls)
type: bool default: --notrace
--lazy (use lazy compilation)
type: bool default: --lazy
--lazy-eval (use lazy compilation during eval)
type: bool default: --lazy-eval
--lazy-streaming (use lazy compilation during streaming compilation)
type: bool default: --lazy-streaming
--max-lazy (ignore eager compilation hints)
type: bool default: --nomax-lazy
--trace-opt (trace optimized compilation)
type: bool default: --notrace-opt
--trace-opt-verbose (extra verbose optimized compilation tracing)
type: bool default: --notrace-opt-verbose
--trace-opt-stats (trace optimized compilation statistics)
type: bool default: --notrace-opt-stats
--trace-deopt (trace deoptimization)
type: bool default: --notrace-deopt
--log-deopt (log deoptimization)
type: bool default: --nolog-deopt
--trace-deopt-verbose (extra verbose deoptimization tracing)
type: bool default: --notrace-deopt-verbose
--trace-file-names (include file names in trace-opt/trace-deopt output)
type: bool default: --notrace-file-names
--always-opt (always try to optimize functions)
type: bool default: --noalways-opt
--always-osr (always try to OSR functions)
type: bool default: --noalways-osr
--prepare-always-opt (prepare for turning on always opt)
type: bool default: --noprepare-always-opt
--trace-serializer (print code serializer trace)
type: bool default: --notrace-serializer
--compilation-cache (enable compilation cache)
type: bool default: --compilation-cache
--cache-prototype-transitions (cache prototype transitions)
type: bool default: --cache-prototype-transitions
--lazy-compile-dispatcher (enable compiler dispatcher)
type: bool default: --nolazy-compile-dispatcher
--lazy-compile-dispatcher-max-threads (max threads for compiler dispatcher (0 for unbounded))
type: uint default: --lazy-compile-dispatcher-max-threads=0
--trace-compiler-dispatcher (trace compiler dispatcher activity)
type: bool default: --notrace-compiler-dispatcher
--parallel-compile-tasks-for-eager-toplevel (spawn parallel compile tasks for eagerly compiled, top-level functions)
type: bool default: --noparallel-compile-tasks-for-eager-toplevel
--parallel-compile-tasks-for-lazy (spawn parallel compile tasks for all lazily compiled functions)
type: bool default: --noparallel-compile-tasks-for-lazy
--cpu-profiler-sampling-interval (CPU profiler sampling interval in microseconds)
type: int default: --cpu-profiler-sampling-interval=1000
--trace-side-effect-free-debug-evaluate (print debug messages for side-effect-free debug-evaluate for testing)
type: bool default: --notrace-side-effect-free-debug-evaluate
--hard-abort (abort by crashing)
type: bool default: --hard-abort
--experimental-async-stack-tagging-api (enable experimental async stacks tagging API)
type: bool default: --noexperimental-async-stack-tagging-api
--log-colour (When logging, try to use coloured output.)
type: bool default: --log-colour
--expose-inspector-scripts (expose injected-script-source.js for debugging)
type: bool default: --noexpose-inspector-scripts
--stack-size (default size of stack region v8 is allowed to use (in kBytes))
type: int default: --stack-size=864
--max-stack-trace-source-length (maximum length of function source code printed in a stack trace.)
type: int default: --max-stack-trace-source-length=300
--clear-exceptions-on-js-entry (clear pending exceptions when entering JavaScript)
type: bool default: --noclear-exceptions-on-js-entry
--histogram-interval (time interval in ms for aggregating memory histograms)
type: int default: --histogram-interval=600000
--heap-profiler-trace-objects (Dump heap object allocations/movements/size_updates)
type: bool default: --noheap-profiler-trace-objects
--heap-profiler-use-embedder-graph (Use the new EmbedderGraph API to get embedder nodes)
type: bool default: --heap-profiler-use-embedder-graph
--heap-snapshot-string-limit (truncate strings to this length in the heap snapshot)
type: int default: --heap-snapshot-string-limit=1024
--heap-profiler-show-hidden-objects (use 'native' rather than 'hidden' node type in snapshot)
type: bool default: --noheap-profiler-show-hidden-objects
--sampling-heap-profiler-suppress-randomness (Use constant sample intervals to eliminate test flakiness)
type: bool default: --nosampling-heap-profiler-suppress-randomness
--use-idle-notification (Use idle notification to reduce memory footprint.)
type: bool default: --use-idle-notification
--log-ic (Log inline cache state transitions for tools/ic-processor)
type: bool default: --nolog-ic
--max-valid-polymorphic-map-count (maximum number of valid maps to track in POLYMORPHIC state)
type: int default: --max-valid-polymorphic-map-count=4
--native-code-counters (generate extra code for manipulating stats counters)
type: bool default: --nonative-code-counters
--super-ic (use an IC for super property loads)
type: bool default: --super-ic
--enable-mega-dom-ic (use MegaDOM IC state for API objects)
type: bool default: --noenable-mega-dom-ic
--trace-prototype-users (Trace updates to prototype user tracking)
type: bool default: --notrace-prototype-users
--trace-for-in-enumerate (Trace for-in enumerate slow-paths)
type: bool default: --notrace-for-in-enumerate
--log-maps (Log map creation)
type: bool default: --nolog-maps
--log-maps-details (Also log map details)
type: bool default: --log-maps-details
--allow-natives-syntax (allow natives syntax)
type: bool default: --noallow-natives-syntax
--allow-natives-for-differential-fuzzing (allow only natives explicitly allowlisted for differential fuzzers)
type: bool default: --noallow-natives-for-differential-fuzzing
--parse-only (only parse the sources)
type: bool default: --noparse-only
--sim-abort-on-bad-auth (Stop execution when a pointer authentication fails in the ARM64 simulator.)
type: bool default: --sim-abort-on-bad-auth
--async-stack-traces (include async stack traces in Error.stack)
type: bool default: --async-stack-traces
--stack-trace-on-illegal (print stack trace when an illegal exception is thrown)
type: bool default: --nostack-trace-on-illegal
--abort-on-uncaught-exception (abort program (dump core) when an uncaught exception is thrown)
type: bool default: --noabort-on-uncaught-exception
--correctness-fuzzer-suppressions (Suppress certain unspecified behaviors to ease correctness fuzzing: Abort program when the stack overflows or a string exceeds maximum length (as opposed to throwing RangeError). Use a fixed suppression string for error messages.)
type: bool default: --nocorrectness-fuzzer-suppressions
--rehash-snapshot (rehash strings from the snapshot to override the baked-in seed)
type: bool default: --rehash-snapshot
--hash-seed (Fixed seed to use to hash property keys (0 means random)(with snapshots this option cannot override the baked-in seed))
type: uint64 default: --hash-seed=0
--random-seed (Default seed for initializing random generator (0, the default, means to use system random).)
type: int default: --random-seed=0
--fuzzer-random-seed (Default seed for initializing fuzzer random generator (0, the default, means to use v8's random number generator seed).)
type: int default: --fuzzer-random-seed=0
--trace-rail (trace RAIL mode)
type: bool default: --notrace-rail
--print-all-exceptions (print exception object and stack trace on each thrown exception)
type: bool default: --noprint-all-exceptions
--detailed-error-stack-trace (includes arguments for each function call in the error stack frames array)
type: bool default: --nodetailed-error-stack-trace
--adjust-os-scheduling-parameters (adjust OS specific scheduling params for the isolate)
type: bool default: --adjust-os-scheduling-parameters
--experimental-flush-embedded-blob-icache (Used in an experiment to evaluate icache flushing on certain CPUs)
type: bool default: --experimental-flush-embedded-blob-icache
--short-builtin-calls (Put embedded builtins code into the code range for shorter builtin calls/jumps if system has >=4GB memory)
type: bool default: --short-builtin-calls
--runtime-call-stats (report runtime call counts and times)
type: bool default: --noruntime-call-stats
--rcs (report runtime call counts and times)
type: bool default: --norcs
--rcs-cpu-time (report runtime times in cpu time (the default is wall time))
type: bool default: --norcs-cpu-time
--verify-snapshot-checksum (Verify snapshot checksums when deserializing snapshots. Enable checksum creation and verification for code caches.)
type: bool default: --verify-snapshot-checksum
--profile-deserialization (Print the time it takes to deserialize the snapshot.)
type: bool default: --noprofile-deserialization
--serialization-statistics (Collect statistics on serialized objects.)
type: bool default: --noserialization-statistics
--regexp-optimization (generate optimized regexp code)
type: bool default: --regexp-optimization
--regexp-interpret-all (interpret all regexp code)
type: bool default: --noregexp-interpret-all
--regexp-tier-up (enable regexp interpreter and tier up to the compiler after the number of executions set by the tier up ticks flag)
type: bool default: --regexp-tier-up
--regexp-tier-up-ticks (set the number of executions for the regexp interpreter before tiering-up to the compiler)
type: int default: --regexp-tier-up-ticks=1
--regexp-peephole-optimization (enable peephole optimization for regexp bytecode)
type: bool default: --regexp-peephole-optimization
--trace-regexp-peephole-optimization (trace regexp bytecode peephole optimization)
type: bool default: --notrace-regexp-peephole-optimization
--trace-regexp-bytecodes (trace regexp bytecode execution)
type: bool default: --notrace-regexp-bytecodes
--trace-regexp-assembler (trace regexp macro assembler calls.)
type: bool default: --notrace-regexp-assembler
--trace-regexp-parser (trace regexp parsing)
type: bool default: --notrace-regexp-parser
--trace-regexp-tier-up (trace regexp tiering up execution)
type: bool default: --notrace-regexp-tier-up
--trace-regexp-graph (trace the regexp graph)
type: bool default: --notrace-regexp-graph
--enable-experimental-regexp-engine (recognize regexps with 'l' flag, run them on experimental engine)
type: bool default: --noenable-experimental-regexp-engine
--default-to-experimental-regexp-engine (run regexps with the experimental engine where possible)
type: bool default: --nodefault-to-experimental-regexp-engine
--trace-experimental-regexp-engine (trace execution of experimental regexp engine)
type: bool default: --notrace-experimental-regexp-engine
--enable-experimental-regexp-engine-on-excessive-backtracks (fall back to a breadth-first regexp engine on excessive backtracking)
type: bool default: --noenable-experimental-regexp-engine-on-excessive-backtracks
--regexp-backtracks-before-fallback (number of backtracks during regexp execution before fall back to experimental engine if enable_experimental_regexp_engine_on_excessive_backtracks is set)
type: uint default: --regexp-backtracks-before-fallback=50000
--testing-bool-flag (testing_bool_flag)
type: bool default: --testing-bool-flag
--testing-maybe-bool-flag (testing_maybe_bool_flag)
type: maybe_bool default: --testing-maybe-bool-flag=unset
--testing-int-flag (testing_int_flag)
type: int default: --testing-int-flag=13
--testing-float-flag (float-flag)
type: float default: --testing-float-flag=2.5
--testing-string-flag (string-flag)
type: string default: --testing-string-flag="Hello, world!"
--testing-prng-seed (Seed used for threading test randomness)
type: int default: --testing-prng-seed=42
--testing-d8-test-runner (test runner turns on this flag to enable a check that the function was prepared for optimization before marking it for optimization)
type: bool default: --notesting-d8-test-runner
--fuzzing (Fuzzers use this flag to signal that they are ... fuzzing. This causes intrinsics to fail silently (e.g. return undefined) on invalid usage.)
type: bool default: --nofuzzing
--embedded-src (Path for the generated embedded data file. (mksnapshot only))
type: string default: --embedded-src=""
--embedded-variant (Label to disambiguate symbols in embedded data file. (mksnapshot only))
type: string default: --embedded-variant=""
--startup-src (Write V8 startup as C++ src. (mksnapshot only))
type: string default: --startup-src=""
--startup-blob (Write V8 startup blob file. (mksnapshot only))
type: string default: --startup-blob=""
--target-arch (The mksnapshot target arch. (mksnapshot only))
type: string default: --target-arch=""
--target-os (The mksnapshot target os. (mksnapshot only))
type: string default: --target-os=""
--target-is-simulator (Instruct mksnapshot that the target is meant to run in the simulator and it can generate simulator-specific instructions. (mksnapshot only))
type: bool default: --notarget-is-simulator
--turbo-profiling-log-file (Path of the input file containing basic block counters for builtins. (mksnapshot only))
type: string default: --turbo-profiling-log-file=""
--text-is-readable (Whether the .text section of binary can be read)
type: bool default: --text-is-readable
--trace-minor-mc-parallel-marking (trace parallel marking for the young generation)
type: bool default: --notrace-minor-mc-parallel-marking
--minor-mc (perform young generation mark compact GCs)
type: bool default: --nominor-mc
--help (Print usage message, including flags, on console)
type: bool default: --help
--print-flag-values (Print all flag values of V8)
type: bool default: --noprint-flag-values
--slow-histograms (Enable slow histograms with more overhead.)
type: bool default: --noslow-histograms
--use-external-strings (Use external strings for source code)
type: bool default: --nouse-external-strings
--map-counters (Map counters to a file)
type: string default: --map-counters=""
--mock-arraybuffer-allocator (Use a mock ArrayBuffer allocator for testing.)
type: bool default: --nomock-arraybuffer-allocator
--mock-arraybuffer-allocator-limit (Memory limit for mock ArrayBuffer allocator used to simulate OOM for testing.)
type: size_t default: --mock-arraybuffer-allocator-limit=0
--logfile (Specify the name of the log file, use '-' for console, '+' for a temporary file.)
type: string default: --logfile="v8.log"
--logfile-per-isolate (Separate log files for each isolate.)
type: bool default: --logfile-per-isolate
--log (Minimal logging (no API, code, GC, suspect, or handles samples).)
type: bool default: --nolog
--log-all (Log all events to the log file.)
type: bool default: --nolog-all
--log-api (Log API events to the log file.)
type: bool default: --nolog-api
--log-code (Log code events to the log file without profiling.)
type: bool default: --nolog-code
--log-code-disassemble (Log all disassembled code to the log file.)
type: bool default: --nolog-code-disassemble
--log-handles (Log global handle events.)
type: bool default: --nolog-handles
--log-suspect (Log suspect operations.)
type: bool default: --nolog-suspect
--log-source-code (Log source code.)
type: bool default: --nolog-source-code
--log-function-events (Log function events (parse, compile, execute) separately.)
type: bool default: --nolog-function-events
--detailed-line-info (Always generate detailed line information for CPU profiling.)
type: bool default: --nodetailed-line-info
--prof-sampling-interval (Interval for --prof samples (in microseconds).)
type: int default: --prof-sampling-interval=1000
--prof-cpp (Like --prof, but ignore generated code.)
type: bool default: --noprof-cpp
--prof-browser-mode (Used with --prof, turns on browser-compatible mode for profiling.)
type: bool default: --prof-browser-mode
--prof (Log statistical profiling information (implies --log-code).)
type: bool default: --noprof
--ll-prof (Enable low-level linux profiler.)
type: bool default: --noll-prof
--gc-fake-mmap (Specify the name of the file for fake gc mmap used in ll_prof)
type: string default: --gc-fake-mmap="/tmp/__v8_gc__"
--log-internal-timer-events (Time internal events.)
type: bool default: --nolog-internal-timer-events
--redirect-code-traces (output deopt information and disassembly into file code-<pid>-<isolate id>.asm)
type: bool default: --noredirect-code-traces
--redirect-code-traces-to (output deopt information and disassembly into the given file)
type: string default: --redirect-code-traces-to=""
--print-opt-source (print source code of optimized and inlined functions)
type: bool default: --noprint-opt-source
--vtune-prof-annotate-wasm (Used when v8_enable_vtunejit is enabled, load wasm source map and provide annotate support (experimental).)
type: bool default: --novtune-prof-annotate-wasm
--win64-unwinding-info (Enable unwinding info for Windows/x64)
type: bool default: --win64-unwinding-info
--interpreted-frames-native-stack (Show interpreted frames on the native stack (useful for external profilers).)
type: bool default: --nointerpreted-frames-native-stack
--enable-system-instrumentation (Enable platform-specific profiling.)
type: bool default: --noenable-system-instrumentation
--predictable (enable predictable mode)
type: bool default: --nopredictable
--predictable-gc-schedule (Predictable garbage collection schedule. Fixes heap growing, idle, and memory reducing behavior.)
type: bool default: --nopredictable-gc-schedule
--single-threaded (disable the use of background tasks)
type: bool default: --nosingle-threaded
--single-threaded-gc (disable the use of background gc tasks)
type: bool default: --nosingle-threaded-gc
--experimental-web-snapshots (interpret scripts as web snapshots if they start with a magic number)
type: bool default: --noexperimental-web-snapshots