Hi,
I started playing with the current wasm implementation and there are some
things that are not clear for me.
If I compile this wast i get the expected result:
(module
(func $add (param $x f32) (param $y f32) (result f32) (f32.add (get_local
$x) (get_local $y)))
(export "add" (func $add))
)
module = Wasm.instantiateModule(new Uint8Array(buffer), {});
module.exports.add(1,2) // => 3
But when I try to compile from C, I get an exception "Error: memory access
out of bounds"
This is the C source:
double add(double a, double b) { return a + b; }
Fist I compile it to llvm ir:
; ModuleID = 'sample.c'
source_filename = "sample.c"
target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
target triple = "wasm32"
; Function Attrs: nounwind
define hidden double @add(double %a, double %b) #0 {
entry:
%a.addr = alloca double, align 8
%b.addr = alloca double, align 8
store double %a, double* %a.addr, align 8
store double %b, double* %b.addr, align 8
%0 = load double, double* %a.addr, align 8
%1 = load double, double* %b.addr, align 8
%add = fadd double %0, %1
ret double %add
}
attributes #0 = { nounwind "correctly-rounded-divide-sqrt-fp-math"="false"
"disable-tail-calls"="false" "less-precise-fpmad"="false"
"no-frame-pointer-elim"="false" "no-infs-fp-math"="false"
"no-jump-tables"="false" "no-nans-fp-math"="false"
"no-signed-zeros-fp-math"="false" "no-trapping-math"="false"
"stack-protector-buffer-size"="8" "target-cpu"="generic"
"unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.ident = !{!0}
!0 = !{!"clang version 4.0.0 (http://llvm.org/git/clang.git
b1b3141a30d56f4feb3cc68f57d1ebaf6fbad246) (http://llvm.org/git/llvm.git
cf04e5f0f84bd44c375bf866d777708df39935df)"}
Then to .s:
.text
.file "sample.ll"
.hidden add
.globl add
.type add,@function
add: # @add
.param f64, f64
.result f64
.local i32
# BB#0: # %entry
i32.const $push2=, 0
i32.load $push3=, __stack_pointer($pop2)
i32.const $push4=, 16
i32.sub $push6=, $pop3, $pop4
tee_local $push5=, $2=, $pop6
f64.store $drop=, 8($pop5), $0
f64.store $drop=, 0($2), $1
f64.load $push0=, 8($2)
f64.add $push1=, $pop0, $1
# fallthrough-return: $pop1
.endfunc
.Lfunc_end0:
.size add, .Lfunc_end0-add
.ident "clang version 4.0.0 (http://llvm.org/git/clang.git
b1b3141a30d56f4feb3cc68f57d1ebaf6fbad246) (http://llvm.org/git/llvm.git
cf04e5f0f84bd44c375bf866d777708df39935df)"
Then i use binaryen s2wast:
(module
(memory $0 1)
(export "memory" (memory $0))
(export "add" (func $add))
(table 0 anyfunc)
(func $add (param $0 f64) (param $1 f64) (result f64)
(local $2 i32)
(f64.store offset=8
(tee_local $2
(i32.sub
(i32.load offset=4
(i32.const 0)
)
(i32.const 16)
)
)
(get_local $0)
)
(f64.store
(get_local $2)
(get_local $1)
)
(f64.add
(f64.load offset=8
(get_local $2)
)
(get_local $1)
)
)
)
And finally use wabt to get wasm file.
If I try to run the result in Chrome Canary i get "Error: memory access
out of bounds"
My goal is to be able to pass ArrayBuffers and other args from JS to wasm
module and to be able to write the code in C. Can someone help me to solve
this issue and maybe point to some useful resources. At this moment it is
hard to find any working examples.
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