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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [GlobalISel][AArch64] i1 value in aggregate not zero-extend prior to store"
href="https://bugs.llvm.org/show_bug.cgi?id=37397">37397</a>
</td>
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<th>Summary</th>
<td>[GlobalISel][AArch64] i1 value in aggregate not zero-extend prior to store
</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: AArch64
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>tstellar@redhat.com
</td>
</tr>
<tr>
<th>CC</th>
<td>efriedma@codeaurora.org, jistone@redhat.com, llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Blocks</th>
<td>36649
</td>
</tr></table>
<p>
<div>
<pre>This testcase comes from <a href="https://github.com/rust-lang/rust/issues/50516">https://github.com/rust-lang/rust/issues/50516</a> and
shows that GlobalISel does not zero-extend an i1 value to 8-bits prior to
writing it to memory:
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-gnu"
define void @i1_store() {
start:
%tmp0 = alloca { i32, i1 }, align 4
%tmp1 = call { i32, i1 } @foo()
store { i32, i1 } %tmp1, { i32, i1 }* %tmp0, align 4
ret void
}
declare { i32, i1 } @foo()
llc -O0 gives us:
sub sp, sp, #32 // =32
str x30, [sp, #16] // 8-byte Folded Spill
.cfi_def_cfa_offset 32
.cfi_offset w30, -16
bl foo
// implicit-def: $x8
mov w9, w0
bfxil x8, x9, #0, #32
mov w9, w1
bfi x8, x9, #32, #1
str x8, [sp, #8]
i1 values are stored in memory as 8-bit values, but it is expected that value
will be either 0x0 or 0x1. In this case, since Bits 33-39 of x8 remain
uninitialized, when this value is loaded there will be random values in the
high 7-bits.
Fast-ISel seems to handle this test case correctly:
sub sp, sp, #32 // =32
str x30, [sp, #16] // 8-byte Folded Spill
.cfi_def_cfa_offset 32
.cfi_offset w30, -16
bl foo
str w0, [sp, #8]
and w0, w1, #0x1
strb w0, [sp, #12]
ldr x30, [sp, #16] // 8-byte Folded Reload
add sp, sp, #32 // =32
ret</pre>
</div>
</p>
<div id="referenced">
<hr style="border: 1px dashed #969696">
<b>Referenced Bugs:</b>
<ul>
<li>
[<a class="bz_bug_link
bz_status_NEW "
title="NEW - [meta] 6.0.1 Release Blockers"
href="https://bugs.llvm.org/show_bug.cgi?id=36649">Bug 36649</a>] [meta] 6.0.1 Release Blockers
</li>
</ul>
</div>
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