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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 - Missed optimization: fmax(a+n, b+n)"
href="https://bugs.llvm.org/show_bug.cgi?id=37403">37403</a>
</td>
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<tr>
<th>Summary</th>
<td>Missed optimization: fmax(a+n, b+n)
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>6.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<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>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>m-takahiro@jp.fujitsu.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>I compiled the following code by clang (tags/RELEASE_600/final 327104).
Option is '-Ofast -march=native'.
#include <math.h>
double foo(double a, double b, const double n) {
return fmax(a + n, b + n);
}
Generated IRs is as follows.
; Function Attrs: nounwind readnone uwtable
define double @foo(double, double, double) local_unnamed_addr #0 {
%4 = fadd fast double %2, %0
%5 = fadd fast double %2, %1
%6 = tail call fast double @llvm.maxnum.f64(double %4, double %5)
ret double %6
}
I think the above IRs can be simplified like the following IR when
'-ffast-math' is enabled.
; Function Attrs: nounwind readnone uwtable
define double @foo1(double, double, double) local_unnamed_addr #0 {
%3 = tail call fast double @llvm.maxnum.f64(double %0, double %1)
%4 = fadd fast double %2, %3
ret double %4
}
The same occurs about fmin.
#include <math.h>
double foo(double a, double b, const double n) {
return fmin(a + n, b + n);
}
-->
; Function Attrs: nounwind readnone uwtable
define double @foo(double, double, double) local_unnamed_addr #0 {
%4 = fadd fast double %2, %0
%5 = fadd fast double %2, %1
%6 = tail call fast double @llvm.minnum.f64(double %4, double %5)
ret double %6
}</pre>
</div>
</p>
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