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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [ppc] floating point var allocated to integer register"
href="https://llvm.org/bugs/show_bug.cgi?id=25342">25342</a>
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<tr>
<th>Summary</th>
<td>[ppc] floating point var allocated to integer register
</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>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: PowerPC
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>carrot@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15183" name="attach_15183" title="testcase">attachment 15183</a> <a href="attachment.cgi?id=15183&action=edit" title="testcase">[details]</a></span>
testcase
Compile the attached source code with options
~/llvm/obj/bin/clang++ --target=powerpc64le-grtev4-linux-gnu -O2
-fno-strict-aliasing -m64 -mvsx -mcpu=power8 -ffp-contract=fast
llvm generates following code for the inner loop
lfsu 1, 16(22)
addi 24, 24, -2
cmplwi 6, 24, 0
lfsu 2, 16(23)
lxsspx 4, 22, 5
lxsspx 3, 23, 5
stw 25, -112(1) // A
ori 2, 2, 0
lxsspx 5, 0, 6 // B
stw 26, -108(1) // C
xsmulsp 7, 3, 4
ori 2, 2, 0
lxsspx 6, 0, 7 // D
lxsspx 9, 23, 10
lxsspx 8, 22, 10
lxsspx 11, 23, 8
lxsspx 12, 22, 8
xsmaddasp 6, 2, 4
xsmulsp 10, 9, 8
xsmsubasp 7, 2, 1
xsmaddasp 6, 3, 1
xsmsubasp 10, 11, 12
xsaddsp 5, 5, 7
xsmaddasp 6, 11, 8
xsaddsp 13, 5, 10
xsmaddasp 6, 9, 12
stxsspx 13, 0, 11 // E
ori 2, 2, 0
lwz 25, -100(1) // F
stxsspx 6, 0, 12 // G
ori 2, 2, 0
lwz 26, -104(1) // H
bne 6, .LBB0_9
The variable std::complex<float> sum is allocated to integer registers r25,r26.
Before using it, instructions ABCD move it to floating point registers, after
generating new values, instructions EFGH move it back to integer registers.
GCC allocates sum to floating point registers directly.
On power8, llvm generated code is 4.5x slower than gcc.</pre>
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</p>
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