// ./build/linux-x86_64-server-fastdebug/jdk/bin/java -XX:+PrintCompilation -XX:CompileCommand=compileonly,EmptyString::main -XX:CompileCommand=quiet -Xbatch -XX:+PrintOptoAssembly -XX:CompileCommand=IGVPrintLevel,EmptyString::main,3 EmptyString
class EmptyString {
public static void main(String[] args) {
String msg = "";
int x = 0;
for (int i = 0; i < 300_000; ++i) {
if (msg.length() > 0) {
x++;
}
}
System.out.println(x);
}
}here is main in bytecode. OSR comples the loop 7-26. LV1 is String msg = "".
public static void main(java.lang.String[]);
Code:
0: ldc #7 // String
2: astore_1
3: iconst_0
4: istore_2
5: iconst_0
6: istore_3
7: iload_3
8: ldc #9 // int 300000
10: if_icmpge 29
13: aload_1
14: invokevirtual #10 // Method java/lang/String.length:()I
17: ifle 23
20: iinc 2, 1
23: iinc 3, 1
26: goto 7
29: getstatic #16 // Field java/lang/System.out:Ljava/io/PrintStream;
32: iload_2
33: invokevirtual #22 // Method java/io/PrintStream.println:(I)V
36: return
Here are generated OSR in OptoAssembly.
============================= C2-compiled nmethod ==============================
#r018 rsi:rsi : parm 0: rawptr:BotPTR
# -- Old rsp -- Framesize: 48 --
#r591 rsp+44: in_preserve
#r590 rsp+40: return address
#r589 rsp+36: in_preserve
#r588 rsp+32: saved fp register
#r587 rsp+28: pad2, stack alignment
#r586 rsp+24: pad2, stack alignment
#r585 rsp+20: Fixed slot 1
#r584 rsp+16: Fixed slot 0
#r595 rsp+12: spill
#r594 rsp+ 8: spill
#r593 rsp+ 4: spill
#r592 rsp+ 0: spill
#
----------------------- MetaData before Compile_id = 28 ------------------------
{method}
- this oop: 0x00007fd448705308
- method holder: 'EmptyString'
- constants: 0x00007fd448705030 constant pool [37] {0x00007fd448705030} for 'EmptyString' cache=0x00007fd448705430
- access: 0x9 public static
- flags: 0x6080 queued_for_compilation has_loops_flag has_loops_flag_init
- name: 'main'
- signature: '([Ljava/lang/String;)V'
- max stack: 3
- max locals: 4
- size of params: 1
- method size: 14
- highest level: 3
- vtable index: -2
- i2i entry: 0x00007fd490423be0
- adapters: AHE@0x00007fd49816bba0: 0xb i2c: 0x00007fd490532d60 c2i: 0x00007fd490532e1a c2iUV: 0x00007fd490532df5 c2iNCI: 0x00007fd490532e54
- compiled entry 0x00007fd489000c20
- code size: 37
- code start: 0x00007fd4487052d8
- code end (excl): 0x00007fd4487052fd
- method data: 0x00007fd4487054b0
- checked ex length: 0
- linenumber start: 0x00007fd4487052fd
- localvar length: 0
- compiled code: nmethod366 27 3 EmptyString::main (37 bytes)
------------------------ OptoAssembly for Compile_id = 28 -----------------------
#
# void ( rawptr:BotPTR )
#
000 N104: # out( B1 ) <- BLOCK HEAD IS JUNK Freq: 1
000 # breakpoint
nop # 11 bytes pad for loops and calls
010 B1: # out( B8 B2 ) <- BLOCK HEAD IS JUNK Freq: 1
010 # stack bang (144 bytes)
pushq rbp # Save rbp
subq rsp, #32 # Create frame
02a movq RBP, [RSI + #16 (8-bit)] # ptr
02e movl RBX, [RSI + #8 (8-bit)] # int
031 movl R13, [RSI] # int
034 movq RDI, RSI # spill
037 call_leaf,runtime OSR_migration_end
No JVM State Info
#
04c testq RBP, RBP # ptr
04f je,s B8 P=0.000001 C=-1.000000
051 B2: # out( B10 B3 ) <- in( B1 ) Freq: 0.999999
051 movl R10, [RBP + #8 (8-bit)] # compressed klass ptr
055 cmpl R10, narrowklass: precise java/lang/String: 0x00007fd498320c18 (java/io/Serializable,java/lang/Comparable,java/lang/CharSequence,java/lang/constant/Constable,java/lang/constant/ConstantDesc):Constant:exact * # compressed klass ptr
05c jne,u B10 P=0.000001 C=-1.000000
062 B3: # out( B9 B4 ) <- in( B2 ) Freq: 0.999998
062 # checkcastPP of RBP
062 movl R10, [RBP + #20 (8-bit)] # compressed ptr ! Field: java/lang/String.value (constant)
066 movl R11, [R12 + R10 << 3 + #12] (compressed oop addressing) # range
06b NullCheck R10
06b B4: # out( B9 B5 ) <- in( B3 ) Freq: 0.999997
06b movsbl R10, [RBP + #16 (8-bit)] # byte ! Field: java/lang/String.coder (constant)
070 sarxl R11, R11, R10
075 testl R11, R11
078 jg,s B9 P=0.000001 C=-1.000000
07a B5: # out( B7 B6 ) <- in( B4 ) Freq: 0.999996
07a cmpl R13, #300000
081 jge,s B7 P=0.000001 C=40960.000000
083 B6: # out( B7 ) <- in( B5 ) Freq: 0.999995
083 movl R13, #300000 # int
089 B7: # out( N104 ) <- in( B5 B6 ) Freq: 0.999996
089 movl RSI, #-187 # int
08e movl RBP, RBX # spill
090 movl [rsp + #0], R13 # spill
nop # 3 bytes pad for loops and calls
097 call,static wrapper for: uncommon_trap(reason='unstable_if' action='reinterpret' debug_id='0')
# EmptyString::main @ bci:10 (line 6) L[0]=_ L[1]=_ L[2]=RBP L[3]=_ STK[0]=rsp + #0 STK[1]=#300000
# OopMap {off=156/0x9c}
0a4 stop # ShouldNotReachHere
0b8 B8: # out( B9 ) <- in( B1 ) Freq: 1.01328e-06
0b8 xorl RBP, RBP # ptr
0ba B9: # out( N104 ) <- in( B4 B8 B3 ) Freq: 3.03983e-06
0ba movl RSI, #-138 # int
0bf movl [rsp + #0], RBX # spill
0c2 movl [rsp + #4], R13 # spill
0c7 call,static wrapper for: uncommon_trap(reason='predicate' action='maybe_recompile' debug_id='0')
# EmptyString::main @ bci:7 (line 6) L[0]=_ L[1]=RBP L[2]=rsp + #0 L[3]=rsp + #4
# OopMap {rbp=Oop off=204/0xcc}
0d4 stop # ShouldNotReachHere
0e8 B10: # out( N104 ) <- in( B2 ) Freq: 9.99999e-07
0e8 movl RSI, #-115 # int
0ed movl [rsp + #0], RBX # spill
0f0 movl [rsp + #4], R13 # spill
nop # 2 bytes pad for loops and calls
0f7 call,static wrapper for: uncommon_trap(reason='constraint' action='reinterpret' debug_id='0')
# EmptyString::main @ bci:7 (line 6) L[0]=_ L[1]=RBP L[2]=rsp + #0 L[3]=rsp + #4
# OopMap {rbp=Oop off=252/0xfc}
104 stop # ShouldNotReachHere
--------------------------------------------------------------------------------
366 26 % 3 EmptyString::main @ 7 (37 bytes) made not entrant
366 28 % 4 EmptyString::main @ 7 (37 bytes) made not entrant
LoadRange (get the length of an array) node before optimizer
LoadRange after optimizer.
LoadRange after codegen.
