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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [X86] Failure to use condition code result from promoted bitop"
href="https://bugs.llvm.org/show_bug.cgi?id=35413">35413</a>
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<th>Summary</th>
<td>[X86] Failure to use condition code result from promoted bitop
</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>
<tr>
<th>OS</th>
<td>Windows NT
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>llvm-dev@redking.me.uk
</td>
</tr>
<tr>
<th>CC</th>
<td>craig.topper@gmail.com, filcab@gmail.com, llvm-bugs@lists.llvm.org, spatel+llvm@rotateright.com
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</tr></table>
<p>
<div>
<pre>After promoting a OR(i16,i16) to OR(i32,i32) (with signext args), we fail to
realise that we can use the EFLAGS result from the OR to test for zero instead
of creating a separate TESTW.
short bar16();
short foo16(short a, short b) {
if ((a | b) < 0)
return bar16();
return a | b;
}
int bar32();
int foo32(int a, int b) {
if ((a | b) < 0)
return bar32();
return a | b;
}
define signext i16 @foo16(i16 signext, i16 signext) {
%3 = or i16 %1, %0
%4 = icmp slt i16 %3, 0
br i1 %4, label %5, label %7
; <label>:5: ; preds = %2
%6 = tail call signext i16 @bar16()
br label %7
; <label>:7: ; preds = %2, %5
%8 = phi i16 [ %6, %5 ], [ %3, %2 ]
ret i16 %8
}
declare signext i16 @bar16()
define i32 @foo32(i32, i32) {
%3 = or i32 %1, %0
%4 = icmp slt i32 %3, 0
br i1 %4, label %5, label %7
; <label>:5: ; preds = %2
%6 = tail call i32 @bar32()
br label %7
; <label>:7: ; preds = %2, %5
%8 = phi i32 [ %6, %5 ], [ %3, %2 ]
ret i32 %8
}
declare i32 @bar32()
foo16:
orl %esi, %edi
testw %di, %di <<- UNNECESSARY??
je .LBB1_2
movl %edi, %eax
retq
.LBB1_2:
jmp bar16()@PLT # TAILCALL
foo32:
orl %esi, %edi
je .LBB2_2
movl %edi, %eax
retq
.LBB2_2:
jmp bar32()@PLT # TAILCALL</pre>
</div>
</p>
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