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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [SimplifyCFG] failure to sink common function call below if/else"
href="https://llvm.org/bugs/show_bug.cgi?id=28964">28964</a>
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<th>Summary</th>
<td>[SimplifyCFG] failure to sink common function call below if/else
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<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>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Transformation Utilities
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Forking this off from <a class="bz_bug_link
bz_status_NEW "
title="NEW --- - constant function parameter is set to existing value"
href="show_bug.cgi?id=28957">bug 28957</a>:
extern int bar(int);
int foo(int x) {
if (x == 1)
return bar(1);
else
return bar(-1);
}
Or as optimized IR:
define i32 @foo(i32 %x) {
entry:
%cmp = icmp eq i32 %x, 1
br i1 %cmp, label %if.then, label %if.else
if.then:
%call = tail call i32 @bar(i32 1) #2
br label %return
if.else:
%call1 = tail call i32 @bar(i32 -1) #2
br label %return
return:
%retval.0 = phi i32 [ %call, %if.then ], [ %call1, %if.else ]
ret i32 %retval.0
}
declare i32 @bar(i32)
--------------------------------------------------------------------------
I think SimplifyCFG should transform this to the equivalent of:
int goo(int x) {
if (x == 1)
x = 1;
else
x = -1;
return bar(x);
}
which is this in IR:
define i32 @goo(i32 %x) local_unnamed_addr #0 {
%cmp = icmp eq i32 %x, 1
%sel = select i1 %cmp, i32 1, i32 -1
%call = tail call i32 @bar(i32 %sel)
ret i32 %call
}</pre>
</div>
</p>
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