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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Clang's call lowering often coerces pointers to ints, which blocks alias analysis"
href="https://llvm.org/bugs/show_bug.cgi?id=31724">31724</a>
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<th>Summary</th>
<td>Clang's call lowering often coerces pointers to ints, which blocks alias analysis
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</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>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>LLVM Codegen
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>rnk@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Consider this C code:
struct Handle { void *p; };
extern void g(struct Handle);
void f(struct Handle o) { g(o); }
Here are three examples of clang coercing the 'p' field to an int:
$ clang -S -x c --target=ppc64-linux t.cpp -o - -emit-llvm | grep define
define void @f(i64 %o.coerce) #0 {
$ clang -S -x c --target=x86_64-windows t.cpp -o - -emit-llvm | grep define
define void @f(i64 %o.coerce) #0 {
$ clang -S -x c --target=mips-linux t.cpp -o - -emit-llvm | grep define
define void @f(i32 inreg %o.coerce) #0 {
According to dannyb, this is bad, because the ptrtoint calls block alias
analysis.</pre>
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</p>
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