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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [PCG] Redundant stack operations"
href="https://bugs.llvm.org/show_bug.cgi?id=36042">36042</a>
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<th>Summary</th>
<td>[PCG] Redundant stack operations
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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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>
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<th>Reporter</th>
<td>konstantin.belochapka@sony.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Redundant stack operations from clang.
A repro case with command line and disassembly is below.
Source (test.c):
typedef bool (*CallbackFunc)(unsigned int param);
bool Test(CallbackFunc func, unsigned int param)
{
bool x = func(param);
return (x || 1);
}
Command Line:
clang -fomit-frame-pointer -O2 -g -c test.c test.o
Disassembly:
Test: # @Test
.cfi_startproc
# BB#0: # %entry
pushq %rax
.Ltmp1:
.cfi_def_cfa_offset 16
movq %rdi, %rax
movl %esi, %edi
callq *%rax
movb $1, %al
popq %rdx
ret
Notice the redundant 'push rax' (and the 'pop rdx' that seems to go with it).
Please note that the -fomit-frame-pointer is intentional in this
case, btw.. even though it's not actually a leaf function.</pre>
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