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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 - `.fill` handling is slow"
href="https://bugs.llvm.org/show_bug.cgi?id=51632">51632</a>
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<tr>
<th>Summary</th>
<td>`.fill` handling is slow
</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>
<tr>
<th>Component</th>
<td>MC
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nicolasweber@gmx.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Compiling this file takes over 4s on my machine (targeting mach-o in case it
matters):
```
void f();
int main() {
f();
__asm__(".fill 0x10000000"); // 256 MiB, max jump dist on arm64
}
void f() {}
```
Deleting this look in MCObjectStreamer::emitFill():
// Emit now if we can for better errors.
int64_t NonZeroSize = Size > 4 ? 4 : Size;
Expr &= ~0ULL >> (64 - NonZeroSize * 8);
for (uint64_t i = 0, e = IntNumValues; i != e; ++i) {
emitIntValue(Expr, NonZeroSize);
if (NonZeroSize < Size)
emitIntValue(0, Size - NonZeroSize);
}
return;
and making it fall through to the MCFillFragment() case drops that to 0.6s,
which is much better (but still slow -- writing 256 MiB should be ~instant).
Completely deleting it makes some tests fail, possibly because the expression
evaluator can't reason about symbols refering to MCFillFragment (?)</pre>
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