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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Code generation for 128 bit multiplication - MULX"
href="https://bugs.llvm.org/show_bug.cgi?id=41164">41164</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Code generation for 128 bit multiplication - MULX
</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>Linux
</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>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>uint64_t wyhash64_x;
uint64_t wyhash64() {
wyhash64_x += 0x60bee2bee120fc15;
__uint128_t tmp;
tmp = (__uint128_t) wyhash64_x * 0xa3b195354a39b70d;
uint64_t m1 = (tmp >> 64) ^ tmp;
tmp = (__uint128_t)m1 * 0x1b03738712fad5c9;
uint64_t m2 = (tmp >> 64) ^ tmp;
return m2;
}
Clang trunk -O3 -march=haswell
wyhash64(): # @wyhash64()
movabs rcx, 6971258582664805397
add rcx, qword ptr [rip + wyhash64_x]
mov qword ptr [rip + wyhash64_x], rcx
movabs rsi, -6651371118538410227
mov rax, rcx
mul rsi
imul rcx, rsi
xor rcx, rdx
movabs rdx, 1946526487930394057
mov rax, rcx
mul rdx
xor rax, rdx
ret
wyhash64_x:
.quad 0
While ICC and GCC generates nicer code:
wyhash64():
mov rdx, 0x60bee2bee120fc15 #10.3
add rdx, QWORD PTR wyhash64_x[rip] #10.3
mov rax, 0xa3b195354a39b70d #12.3
mov QWORD PTR wyhash64_x[rip], rdx #10.3
mov rsi, 0x1b03738712fad5c9 #14.3
mulx rdx, rcx, rax #12.36
xor rdx, rcx #13.31
mulx rax, rdi, rsi #14.27
xor rax, rdi #15.31
ret</pre>
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