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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Invalid WebAssembly module generation when using alloca"
href="https://bugs.llvm.org/show_bug.cgi?id=35205">35205</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Invalid WebAssembly module generation when using alloca
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: WebAssembly
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>talzion12@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Following is a terminal session showing the problem:
$ cat code.ll
; ModuleID = "bridge-module:bridge-module"
target triple = "wasm32-unknown-unknown-wasm"
target datalayout = ""
declare i32 @"foo"()
define external void @"hello_world"()
{
entry:
%".2" = alloca i32
%".3" = call i32 @"foo"()
ret void
}
$ llc -filetype=obj code.ll
$ wasm2wast code.o
(module
(type (;0;) (func))
(type (;1;) (func (result i32)))
(import "env" "__stack_pointer" (global (;0;) i32))
(import "env" "foo" (func $foo (type 1)))
(func $hello_world (type 0)
(local i32)
get_global 0
i32.const 16
i32.sub
tee_local 0
set_global 0
call $foo
drop
get_local 0
i32.const 16
i32.add
set_global 0)
(table (;0;) 0 anyfunc)
(memory (;0;) 0)
(export "hello_world" (func $hello_world)))
$ node --version
v9.0.0-nightly2017103182790d84f2
$ node
<span class="quote">> var module = new WebAssembly.Module(fs.readFileSync("code.o"))</span >
CompileError: WebAssembly.Module(): Compiling wasm function #1:hello_world
failed: immutable global #0 cannot be assigned @+132
When I try commenting out either the alloca or the call instruction in the
hello_world function, everything works fine. It seems that the set_global
instruction in the resulting WebAssembly is what's causing node to throw an
error.
I'm not sure if this is a bug in LLVM or node.
wasm2wast is a tool from the wabt tools.
I grabbed node from
<a href="https://nodejs.org/download/nightly/v9.0.0-nightly2017103182790d84f2/">https://nodejs.org/download/nightly/v9.0.0-nightly2017103182790d84f2/</a></pre>
</div>
</p>
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