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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Always inliner should not delete dead calls to readonly/readnone functions at -O0"
href="https://bugs.llvm.org/show_bug.cgi?id=32363">32363</a>
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<th>Summary</th>
<td>Always inliner should not delete dead calls to readonly/readnone functions at -O0
</td>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Interprocedural Optimizations
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>rnk@google.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<p>
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<pre>Consider this code:
void readonly(void) __attribute__((__const__));
void readonly(void) {}
void foo(void) { readonly(); }
This code built with 'clang -O0' ends up not calling 'readonly', which is bad
for debugging and dynamic instrumentation tools.
The inliner contains this logic:
// If this call site is dead and it is to a readonly function, we should
// just delete the call instead of trying to inline it, regardless of
// size. This happens because IPSCCP propagates the result out of the
// call and then we're left with the dead call.
if (isInstructionTriviallyDead(CS.getInstruction(), &TLI)) {
DEBUG(dbgs() << " -> Deleting dead call: " << *CS.getInstruction()
<< "\n");
// Update the call graph by deleting the edge from Callee to Caller.
CG[Caller]->removeCallEdgeFor(CS);
CS.getInstruction()->eraseFromParent();
++NumCallsDeleted;
} else {
// We can only inline direct calls to non-declarations.
if (!Callee || Callee->isDeclaration())
continue;
This logic should not be enabled at -O0.</pre>
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