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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 - wasm32: Miscompile of aggregate return containing i128"
href="https://bugs.llvm.org/show_bug.cgi?id=43132">43132</a>
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<th>Summary</th>
<td>wasm32: Miscompile of aggregate return containing i128
</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>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: WebAssembly
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>alex@crichton.co
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>First reported upstream at <a href="https://github.com/rust-lang/rust/issues/63918">https://github.com/rust-lang/rust/issues/63918</a> this
has been minimized to IR that looks like:
; ModuleID = 'foo.ll'
source_filename = "foo.ll"
target triple = "wasm32-unknown-unknown"
@foo = private constant i128 8000000000000000000
define i128 @get() {
start:
%0 = tail call { i64, i128 } @decode(i8* bitcast (i128* @foo to i8*))
%1 = extractvalue { i64, i128 } %0, 1
ret i128 %1
}
declare hidden { i64, i128 } @decode(i8* nocapture readonly)
When compiled with `llc wut.ll -o foo.o -filetype=obj -O2` the generated output
contains:
(func (;1;) (type 0) (param i32)
(local i32)
global.get 0
i32.const 32
i32.sub
local.tee 1
global.set 0
local.get 1
i32.const 8
i32.add
i32.const 0
call 0
local.get 0
local.get 1
i64.load offset=8
i64.store
local.get 1
i32.const 32
i32.add
global.set 0)
but at the end of the function there's only one `i64.store` instead of two, so
I think that the upper or lower bits is missing from the store, meaning that
not all of the i128 bytes were copied over.</pre>
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