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<body><span class="vcard"><a class="email" href="mailto:llvm-dev@redking.me.uk" title="Simon Pilgrim <llvm-dev@redking.me.uk>"> <span class="fn">Simon Pilgrim</span></a>
</span> changed
<a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Redundant memory access in SIMD initialization of small struct"
href="http://bugs.llvm.org/show_bug.cgi?id=20934">bug 20934</a>
<br>
<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Resolution</td>
<td>---
</td>
<td>FIXED
</td>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>NEW
</td>
<td>RESOLVED
</td>
</tr>
<tr>
<td style="text-align:right;">CC</td>
<td>
</td>
<td>llvm-dev@redking.me.uk
</td>
</tr></table>
<p>
<div>
<b><a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Redundant memory access in SIMD initialization of small struct"
href="http://bugs.llvm.org/show_bug.cgi?id=20934#c3">Comment # 3</a>
on <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED FIXED - Redundant memory access in SIMD initialization of small struct"
href="http://bugs.llvm.org/show_bug.cgi?id=20934">bug 20934</a>
from <span class="vcard"><a class="email" href="mailto:llvm-dev@redking.me.uk" title="Simon Pilgrim <llvm-dev@redking.me.uk>"> <span class="fn">Simon Pilgrim</span></a>
</span></b>
<pre>Clang 3.5 (-O1) codegen:
func1(): # @func1()
subq $24, %rsp
xorps %xmm0, %xmm0
movaps %xmm0, (%rsp)
leaq (%rsp), %rdi
callq test(void const*)
addq $24, %rsp
retq
func2(): # @func2()
subq $24, %rsp
movups .L_ZZ5func2vE4Bits(%rip), %xmm0
movaps %xmm0, (%rsp)
leaq (%rsp), %rdi
callq test(void const*)
addq $24, %rsp
retq
.L_ZZ5func2vE4Bits:
.quad 0 # 0x0
.long 0 # 0x0
.zero 4
This was fixed in Clang 3.6:
func1(): # @func1()
subq $24, %rsp
xorps %xmm0, %xmm0
movaps %xmm0, (%rsp)
leaq (%rsp), %rdi
callq test(void const*)
addq $24, %rsp
retq
func2(): # @func2()
subq $24, %rsp
xorps %xmm0, %xmm0
movaps %xmm0, (%rsp)
leaq (%rsp), %rdi
callq test(void const*)
addq $24, %rsp
retq
And by clang trunk (r301105) has also avoided that unnecessary LEA:
func1(): # @func1()
subq $24, %rsp
xorps %xmm0, %xmm0
movaps %xmm0, (%rsp)
movq %rsp, %rdi
callq test(void const*)
addq $24, %rsp
retq
func2(): # @func2()
subq $24, %rsp
xorps %xmm0, %xmm0
movaps %xmm0, (%rsp)
movq %rsp, %rdi
callq test(void const*)
addq $24, %rsp
retq</pre>
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