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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - KNL: inline memcpy uses two ymm loads/stores instead of one zmm load/store"
href="https://bugs.llvm.org/show_bug.cgi?id=43240">43240</a>
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<th>Summary</th>
<td>KNL: inline memcpy uses two ymm loads/stores instead of one zmm load/store
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: X86
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>dave@znu.io
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<th>CC</th>
<td>craig.topper@gmail.com, llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, spatel+llvm@rotateright.com
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<pre>The following code generates two ymm loads/stores instead of a single zmm
load/store. This seems specific to knl because skylake-avx512 and
icelake-client both generate the correct code. And yes, this example is derived
from test/CodeGen/X86/memcpy.ll.
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i1)
nounwind
define void @test(i8* nocapture %A, i8* nocapture %B) nounwind optsize
noredzone {
entry:
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %A, i8* %B, i64 64, i1 false)
ret void
}
Expected result (as seen with skylake-avx512 and icelake-client):
vmovups (%rsi), %zmm0
vmovups %zmm0, (%rdi)
retq
Actual result (as seen with knl):
vmovups (%rsi), %ymm0
vmovups 32(%rsi), %ymm1
vmovups %ymm1, 32(%rdi)
vmovups %ymm0, (%rdi)
retq</pre>
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