<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missed optimization in math expression: log10(pow(10.0,x)) == x"
href="https://bugs.llvm.org/show_bug.cgi?id=35706">35706</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missed optimization in math expression: log10(pow(10.0,x)) == x
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</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>
<tr>
<th>Component</th>
<td>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>zamazan4ik@tut.by
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Clang (trunk) with '-O3 -std=c++17 -ffast-math' for this code:
#include <cmath>
double test10(double x)
{
return log10(pow(10.0, x));
}
double test2(double x)
{
return log2(pow(2.0, x));
}
generates this:
.LCPI0_0:
.quad 4621819117588971520 # double 10
test10(double): # @test10(double)
push rax
movaps xmm1, xmm0
movsd xmm0, qword ptr [rip + .LCPI0_0] # xmm0 = mem[0],zero
call pow
pop rax
jmp log10 # TAILCALL
test2(double): # @test2(double)
push rax
call exp2
pop rax
jmp log2 # TAILCALL
But we can simplify it by logX(pow(X,Y)) == Y.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>