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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 --- - Shrink wrapping creates invalid epilogue for Win64 binaries" href="https://urldefense.proofpoint.com/v2/url?u=https-3A__llvm.org_bugs_show-5Fbug.cgi-3Fid-3D24193&d=AwMBaQ&c=8hUWFZcy2Z-Za5rBPlktOQ&r=pF93YEPyB-J_PERP4DUZOJDzFVX5ZQ57vQk33wu0vio&m=MM_a0PUcU5xOo1H1wld-lzB10xWGoqQBYd1jqzXcviY&s=6-FAL1Daj20V_f7rnyAJk8yL27dY9h8SRElheh3HoXw&e=">24193</a>
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<th>Summary</th>
<td>Shrink wrapping creates invalid epilogue for Win64 binaries
</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>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>rnk@google.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>I retargetted this test case from x86-shrink-wrapping.ll:
$ cat test.ll
; ModuleID = '<stdin>'
target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
target triple = "x86_64-windows-gnu"
; Function Attrs: uwtable
define i32 @loopInfoSaveOutsideLoop(i32 %cond, i32 %N) #0 {
entry:
%tobool = icmp eq i32 %cond, 0
br i1 %tobool, label %if.else, label %for.preheader
for.preheader: ; preds = %entry
tail call void asm "nop", ""()
br label %for.body
for.body: ; preds = %for.body,
%for.preheader
%i.05 = phi i32 [ %inc, %for.body ], [ 0, %for.preheader ]
%sum.04 = phi i32 [ %add, %for.body ], [ 0, %for.preheader ]
%call = tail call i32 asm "movl $$1, $0", "=r,~{ebx}"()
%add = add nsw i32 %call, %sum.04
%inc = add nuw nsw i32 %i.05, 1
%exitcond = icmp eq i32 %inc, 10
br i1 %exitcond, label %for.end, label %for.body
for.end: ; preds = %for.body
tail call void asm "nop", "~{ebx}"()
%shl = shl i32 %add, 3
br label %if.end
if.else: ; preds = %entry
%mul = shl nsw i32 %N, 1
br label %if.end
if.end: ; preds = %if.else, %for.end
%sum.1 = phi i32 [ %shl, %for.end ], [ %mul, %if.else ]
ret i32 %sum.1
}
attributes #0 = { uwtable }
It produces an epilogue with a register-to-register move after starting to pop
CSRs, which is illegal:
$ llc -enable-shrink-wrap=true test.ll -o - | grep -A4 popq
popq %rbx
movl %esi, %eax ; <-- not allowed by win64 epilogue rules
retq
.LBB0_4: # %if.else
addl %esi, %esi
We might want to try to make the win64 epilogue more generally resilient to
other MI passes in order to fix this.</pre>
</div>
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