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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Misoptimizations caused by "[ARM] Fix conditions for lowering to S[LR]I""
href="https://bugs.llvm.org/show_bug.cgi?id=45610">45610</a>
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<th>Summary</th>
<td>Misoptimizations caused by "[ARM] Fix conditions for lowering to S[LR]I"
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<th>Product</th>
<td>libraries
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Backend: AArch64
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>martin@martin.st
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<th>CC</th>
<td>arnaud.degrandmaison@arm.com, llvm-bugs@lists.llvm.org, smithp352@googlemail.com, Ties.Stuij@arm.com
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<pre>This commit, "[ARM] Fix conditions for lowering to S[LR]I"
<a href="https://reviews.llvm.org/D77387">https://reviews.llvm.org/D77387</a>, causes misoptimizations to the following
function:
$ cat test.c
void rgb16to24(const unsigned char *src, unsigned char *dst, int src_size) {
unsigned char *d = dst;
const unsigned short *s = (const unsigned short *)src;
const unsigned short *end = s + src_size / 2;
while (s < end) {
unsigned short bgr = *s++;
*d++ = ((bgr&0xF800)>>8) | ((bgr&0xF800)>>13);
*d++ = ((bgr&0x07E0)>>3) | ((bgr&0x07E0)>> 9);
*d++ = ((bgr&0x001F)<<3) | ((bgr&0x001F)>> 2);
}
}
Compiled e.g. like this:
$ clang -target aarch64-linux-gnu -S -O3 test.c -o test.s
I haven't pinpointed which bit of the change in the output is wrong, but
running the function as part of a testsuite points it out as incorrect.</pre>
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