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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 - failed to eliminate conditional memops"
href="https://bugs.llvm.org/show_bug.cgi?id=39603">39603</a>
</td>
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<tr>
<th>Summary</th>
<td>failed to eliminate conditional memops
</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>
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<th>OS</th>
<td>All
</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>
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<th>Reporter</th>
<td>spatel+llvm@rotateright.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>This probably doesn't do anything for <a class="bz_bug_link
bz_status_NEW "
title="NEW - vectorization differences"
href="show_bug.cgi?id=39597">bug 39597</a>, but we're missing some
fundamental transforms before we get to anything more complicated:
void always_store(int* x, int exchangeVal) {
*x = (*x != exchangeVal) ? exchangeVal : *x;
}
void never_store(int* x, int exchangeVal) {
*x = (*x == exchangeVal) ? exchangeVal : *x;
}
void conditional_always_store(int* x, int exchangeVal) {
if (*x != exchangeVal)
*x = exchangeVal;
}
void conditional_never_store(int* x, int exchangeVal) {
if (*x == exchangeVal)
*x = exchangeVal;
}
<a href="https://godbolt.org/z/En099n">https://godbolt.org/z/En099n</a>
As optimized IR:
define void @always_store(i32* nocapture %x, i32 %exchangeVal) {
store i32 %exchangeVal, i32* %x, align 4
ret void
}
define void @never_store(i32* nocapture %x, i32 %exchangeVal) {
ret void
}
define void @conditional_always_store(i32* nocapture %x, i32 %exchangeVal) {
entry:
%0 = load i32, i32* %x, align 4
%cmp = icmp eq i32 %0, %exchangeVal
br i1 %cmp, label %if.end, label %if.then
if.then:
store i32 %exchangeVal, i32* %x, align 4
br label %if.end
if.end:
ret void
}
define void @conditional_never_store(i32* nocapture %x, i32 %exchangeVal) {
entry:
%0 = load i32, i32* %x, align 4
%cmp = icmp eq i32 %0, %exchangeVal
br i1 %cmp, label %if.then, label %if.end
if.then:
store i32 %exchangeVal, i32* %x, align 4
br label %if.end
if.end:
ret void
}</pre>
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</p>
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