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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Code generation for __atomic_and_fetch() contains duplicates"
href="https://llvm.org/bugs/show_bug.cgi?id=30621">30621</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Code generation for __atomic_and_fetch() contains duplicates
</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>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>Yunzhong_Gao@playstation.sony.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>I was testing with trunk r283366.
Here is the test program (atomic.c)
short test(short *ptr, short val, int model) {
return __atomic_and_fetch(ptr, val, model);
}
=========================================
Here is the code generated by GCC 4.8.4
test:
movzwl (%rdi), %eax
movzwl %si, %esi
.L2:
movl %eax, %edx
andl %esi, %edx
lock cmpxchgw %dx, (%rdi)
jne .L2
movl %edx, %eax
ret
=========================================
Here is the code generated by clang:
test: # @test
decl %edx
cmpl $4, %edx
ja .LBB0_2
jmpq *.LJTI0_0(,%rdx,8)
.LBB0_4: # %acquire
movw (%rdi), %ax
.p2align 4, 0x90
.LBB0_5: # %atomicrmw.start6
# =>This Inner Loop Header: Depth=1
movl %eax, %ecx
andl %esi, %ecx
# kill: %AX<def> %AX<kill> %EAX<kill>
lock cmpxchgw %cx, (%rdi)
# kill: %AX<def> %AX<kill> %EAX<def>
jne .LBB0_5
jmp .LBB0_12
.LBB0_2: # %monotonic
movw (%rdi), %ax
.p2align 4, 0x90
.LBB0_3: # %atomicrmw.start
# =>This Inner Loop Header: Depth=1
movl %eax, %ecx
andl %esi, %ecx
# kill: %AX<def> %AX<kill> %EAX<kill>
lock cmpxchgw %cx, (%rdi)
# kill: %AX<def> %AX<kill> %EAX<def>
jne .LBB0_3
jmp .LBB0_12
.LBB0_6: # %release
movw (%rdi), %ax
.p2align 4, 0x90
.LBB0_7: # %atomicrmw.start12
# =>This Inner Loop Header: Depth=1
movl %eax, %ecx
andl %esi, %ecx
# kill: %AX<def> %AX<kill> %EAX<kill>
lock cmpxchgw %cx, (%rdi)
# kill: %AX<def> %AX<kill> %EAX<def>
jne .LBB0_7
jmp .LBB0_12
.LBB0_8: # %acqrel
movw (%rdi), %ax
.p2align 4, 0x90
.LBB0_9: # %atomicrmw.start18
# =>This Inner Loop Header: Depth=1
movl %eax, %ecx
andl %esi, %ecx
# kill: %AX<def> %AX<kill> %EAX<kill>
lock cmpxchgw %cx, (%rdi)
# kill: %AX<def> %AX<kill> %EAX<def>
jne .LBB0_9
jmp .LBB0_12
.LBB0_10: # %seqcst
movw (%rdi), %ax
.p2align 4, 0x90
.LBB0_11: # %atomicrmw.start24
# =>This Inner Loop Header: Depth=1
movl %eax, %ecx
andl %esi, %ecx
# kill: %AX<def> %AX<kill> %EAX<kill>
lock cmpxchgw %cx, (%rdi)
# kill: %AX<def> %AX<kill> %EAX<def>
jne .LBB0_11
.LBB0_12: # %atomic.continue
andl %esi, %eax
retq
It looks to me that many of these loop bodies are identical and can
be merged? For example, the .LBB0_5 block, the .LBB0_3 block, the
.LBB0_7 block, the .LBB0_9 block and the .LBB0_11 block.
Using a size optimization switch like -Os or -Oz does not seem to help.</pre>
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