Using WebAssembly in LLVM

!wasmllvm.md

NOTE: the content is out-of-date. All development is moved to the https://github.com/yurydelendik/wasmception

Using WebAssembly in LLVM

Compiling

# locations, e.g.
export WORKDIR=~/llvmwasm; mkdir -p $WORKDIR
export INSTALLDIR=$WORKDIR

# checkout LLVM
cd $WORKDIR
svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm

# checkout clang
cd $WORKDIR/llvm/tools
svn co http://llvm.org/svn/llvm-project/cfe/trunk clang

# checkout lld
svn co http://llvm.org/svn/llvm-project/lld/trunk lld

# build folder (~14 min; ~1 hour /wo -j)
mkdir $WORKDIR/llvm-build
cd $WORKDIR/llvm-build
# For Debug build:
# cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$INSTALLDIR -DLLVM_TARGETS_TO_BUILD= -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=WebAssembly -DCMAKE_BUILD_TYPE=Debug $WORKDIR/llvm
cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$INSTALLDIR -DLLVM_TARGETS_TO_BUILD= -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=WebAssembly $WORKDIR/llvm 
make -j 8

# install llvm
make install

Example

Let's create "fib.c" and compile it, first to LLVM bitcode, then to WebAssembly-like file. (Notice -O2 or above near clang to avoid failure during llc run.)

$INSTALLDIR/bin/clang -emit-llvm --target=wasm32 -Oz fib.c -c -o fib.bc
$INSTALLDIR/bin/llc -asm-verbose=false -o fib.s fib.bc

See output at fib.s.

Convert to WebAssebly s-expressions (needs binaryen s2wasm tool):

$BINARYENDIR/bin/s2wasm fib.s > fib.wast

See output at fib.wast.

References

• http://llvm.org/docs/GettingStarted.html
• http://llvm.org/svn/llvm-project/llvm/trunk/lib/Target/WebAssembly/
• https://github.com/llvm-mirror/llvm/tree/master/test/CodeGen/WebAssembly

compile.sh

#/bin/bash
llvm_root=~/llvmwasm/llvm-build/bin
binaryen_root=~/llvmwasm/binaryen/bin

cfile=$1
bcfile=${cfile%.*}.bc
sfile=${cfile%.*}.s
wastfile=${cfile%.*}.wast

$llvm_root/clang -emit-llvm --target=wasm32 -Oz "$cfile" -c -o "$bcfile"
if [ $? != 0 ];then
  exit 1
fi

$llvm_root/llc -asm-verbose=false -o "$sfile" "$bcfile"
if [ $? != 0 ];then
  exit 2
fi

$binaryen_root/s2wasm "$sfile" > "$wastfile"
if [ $? != 0 ];then
  exit 3
fi

fib.c

int fib(int n) {
  int i, t, a = 0, b = 1;
  for (i = 0; i < n; i++) {
    t = a + b; a = b; b = t;
  }
  return b;
}

fib.wasm0

	.text
	.file	"fib.bc"
	.globl	fib
	.type	fib,@function
fib:
	.param i32
	.result i32
	block $BB0_3
	i32.const 1
	set_local @9, pop
	i32.const 0
	set_local @13, pop
	i32.const -1
	set_local @12, pop
	@0
	set_local @6, pop
	@9
	set_local @14, pop
BB0_1:
	loop $BB0_3
	add @12, @9
	set_local @12, pop
	sge @12, @6
	set_local @11, pop
	brif $BB0_3, @11
	add @14, @13
	set_local @5, pop
	@14
	set_local @13, pop
	@5
	set_local @14, pop
	br $BB0_1
BB0_3:
	return @14
func_end0:
	.size	fib, func_end0-fib

fib.wast

(module
  (import $print_i32 "stdio" "print" (param i32))
  (import $print_f32 "stdio" "print" (param f32))
  (import $print_i64 "stdio" "print" (param i64))
  (import $print_f64 "stdio" "print" (param f64))
  (func $fib
    (param i32)
    (result i32)
    (block $BB0_3
    (set_local @9 (i32.const 1))
    (set_local @13 (i32.const 0))
    (set_local @12 (i32.const -1))
    (set_local @6 (@0))
    (set_local @14 (@9))
    (loop $BB0_1
    (set_local @12 (add @12 @9))
    (set_local @11 (sge @12 @6))
    (brif $BB0_3 @11)
    (set_local @5 (add @14 @13))
    (set_local @13 (@14))
    (set_local @14 (@5))
    (br $BB0_1)
    )
    )
    (return @14)
  )
  (memory 0 0
    (segment 0
      ""
    )
  )
)

Makefile

ROOT_DIR=$(shell pwd)
LLVM_WORKDIR=$(ROOT_DIR)/src/llvm
LLVM_BUILDDIR=$(ROOT_DIR)/build/llvm
BINARYEN_WORKDIR=$(ROOT_DIR)/src/binaryen
BINARYEN_BUILDDIR=$(ROOT_DIR)/build/binaryen
INSTALLDIR=$(ROOT_DIR)/bin

build: build-llvm build-binaryen

clean: clean-llvm clean-binaryen
	rm -rf $(INSTALLDIR)

install: install-llvm install-binaryen

$(LLVM_WORKDIR)/.svn:
	rm -rf $(LLVM_WORKDIR)
	mkdir -p $(LLVM_WORKDIR)
	svn co http://llvm.org/svn/llvm-project/llvm/trunk $(LLVM_WORKDIR)
	svn co http://llvm.org/svn/llvm-project/cfe/trunk $(LLVM_WORKDIR)/tools/clang
	svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk $(LLVM_WORKDIR)/projects/compiler-rt

$(LLVM_BUILDDIR)/Makefile: $(LLVM_WORKDIR)/.svn
	mkdir -p $(LLVM_BUILDDIR)
	cd $(LLVM_BUILDDIR); cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$(INSTALLDIR) -DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=WebAssembly -DLLVM_TARGETS_TO_BUILD= -DCMAKE_BUILD_TYPE=Release $(LLVM_WORKDIR)

build-llvm: $(LLVM_BUILDDIR)/Makefile
	$(MAKE) -C $(LLVM_BUILDDIR) -j 8 clang llc llvm-lib

clean-llvm:
	rm -rf $(LLVM_WORKDIR)
	rm -rf $(LLVM_BUILDDIR)

install-llvm:
	mkdir -p $(INSTALLDIR)
	$(MAKE) -C $(LLVM_BUILDDIR) install-clang install-llc install-llvm-lib

$(BINARYEN_WORKDIR)/.git:
	rm -rf $(BINARYEN_WORKDIR)
	mkdir -p $(BINARYEN_WORKDIR)
	git clone https://github.com/WebAssembly/binaryen $(BINARYEN_WORKDIR)

$(BINARYEN_BUILDDIR)/Makefile: $(BINARYEN_WORKDIR)/.git
	mkdir -p $(BINARYEN_BUILDDIR)
	cd $(BINARYEN_BUILDDIR); cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=$(INSTALLDIR) -DCMAKE_BUILD_TYPE=Release $(BINARYEN_WORKDIR)

build-binaryen: $(BINARYEN_BUILDDIR)/Makefile
	$(MAKE) -C $(BINARYEN_BUILDDIR) -j 8 wasm-as wasm-dis s2wasm

clean-binaryen:
	rm -rf $(BINARYEN_WORKDIR)
        rm -rf $(BINARYEN_BUILDDIR)

install-binaryen:
	mkdir -p $(INSTALLDIR)
	cp $(addprefix $(BINARYEN_BUILDDIR)/bin/, wasm-as wasm-dis s2wasm) $(INSTALLDIR) 

.PHONY: build clean install build-llvm clean-llvm install-llvm build-binaryen clean-binaryen install-binaryen

@yurydelendik
When I use command:

s2wasm fib.s > fib.wast

Console output:

[[function element:]]:
==========
.functype	fib (i32) -> (i32)
	.local  	i32, i32, i32, i32
	i
==========
Abort trap: 6

And the fib.wast file is empty.
Can you tell me why?
My plateform is Mac(Darwin Kernel Version 17.7.0,macOS 10.13.6)