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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86] PostRAScheduler can reorder inline assembly containing x87 instructions with other x87 instructions used to get the results from the inline assembly."
href="https://bugs.llvm.org/show_bug.cgi?id=40539">40539</a>
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<th>Summary</th>
<td>[X86] PostRAScheduler can reorder inline assembly containing x87 instructions with other x87 instructions used to get the results from the inline assembly.
</td>
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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>Windows NT
</td>
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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
</td>
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<th>Reporter</th>
<td>craig.topper@gmail.com
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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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<p>
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<pre>This test case when compiled with -mtriple=i686 -mcpu=pentium4
@f1 = global float 1.000000e+00, align 4
define zeroext i1 @_Z9test_log2v() {
entry:
%0 = load float, float* @f1, align 4
%1 = fpext float %0 to x86_fp80
%2 = tail call x86_fp80 asm "fld1; fxch; fyl2x",
"={st},0,~{st(1)},~{dirflag},~{fpsr},~{flags}"(x86_fp80 %1)
%conv = fptrunc x86_fp80 %2 to float
%3 = fcmp oeq float %conv, 0.000000e+00
ret i1 %3
}
Will generate this assembly
pushl %eax
.cfi_def_cfa_offset 8
flds f1
fstps (%esp)
xorps %xmm0, %xmm0
#APP
fld1
fxch %st(1)
fyl2x
#NO_APP
cmpeqss (%esp), %xmm0
movd %xmm0, %eax
andl $1, %eax
# kill: def $al killed $al killed $eax
popl %ecx
.cfi_def_cfa_offset 4
retl
The fstps instruction needs to be below the inline assembly block. It's
supposed to store the results from the inline assembly.</pre>
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