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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - rL213897 introduced a regression on 32-bit code due to SEXTLOAD not utilized"
href="http://llvm.org/bugs/show_bug.cgi?id=20767">20767</a>
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<th>Summary</th>
<td>rL213897 introduced a regression on 32-bit code due to SEXTLOAD not utilized
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: X86
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>zinovy.nis@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>rL213897 (<a href="http://reviews.llvm.org/rL213897">http://reviews.llvm.org/rL213897</a>) introduced a significant regression
for 32bit code.
<span class="quote">> llc -march=x86 -mcpu=core-avx2 -O2 -o - test.ll</span >
; test.ll
define <4 x i32> @sextload(<4 x i16>* %ptr).
{
entry:
%l = load<4 x i16>* %ptr
%m = sext<4 x i16> %l to <4 x i32>
ret <4 x i32> %m
}
is compiled into:
movl 4(%esp), %eax
movswl 2(%eax), %ecx
movswl (%eax), %edx
vmovd %edx, %xmm0
vpinsrd $1, %ecx, %xmm0, %xmm0
movswl 4(%eax), %ecx
vpinsrd $2, %ecx, %xmm0, %xmm0
movswl 6(%eax), %eax
vpinsrd $3, %eax, %xmm0, %xmm0
retl
Note lots of insert instructions. These instructions appeared due to
if (Subtarget->is64Bit()) {
setLoadExtAction(ISD::SEXTLOAD, MVT::v4i16, Custom);
setLoadExtAction(ISD::SEXTLOAD, MVT::v8i8, Custom);
}
in lib/Target/X86/X86ISelLowering.cpp.
Eliminating "if", we get:
movl 4(%esp), %eax
vpmovsxwd (%eax), %xmm0
retl
which is optimal.</pre>
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