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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 - Labels generated, but no code above 'O0'"
href="https://bugs.llvm.org/show_bug.cgi?id=35508">35508</a>
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<tr>
<th>Summary</th>
<td>Labels generated, but no code above 'O0'
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>5.0
</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>LLVM Codegen
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>martino@theheart.ie
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>While reducing a bug in my LLVM Out-of-Tree sources (v5.0.0), I discovered that
the same problem occurs with the official v4.0.0 and v5.0.0 X86 distributions
for Windows and Linux.
When the following example is compiled with 'clang -S -O0' code is correctly
generated, but with '-O1' and above, only labels are generated with no code
following. No error is reported and the exit code is zero.
The minimal test case I could reduce to is as follows:
void func(int *z) {
int *b = 0;
for (int j = 0; j < 16; j++) {
int c = *b;
c -= *z++;
*b++ = c;
}
}
For X86 this produces only the following code (nothing after "# BB#0:"):
.text
.def @feat.00;
.scl 3;
.type 0;
.endef
.globl @feat.00
@feat.00 = 1
.def _func;
.scl 2;
.type 32;
.endef
.globl _func
.p2align 4, 0x90
_func: # @func
# BB#0:</pre>
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