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<head>
<base href="http://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - 'tbaa vtable pointer' attr is missed for member function pointer deref"
href="http://llvm.org/bugs/show_bug.cgi?id=19113">19113</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>'tbaa vtable pointer' attr is missed for member function pointer deref
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>-New Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dvyukov@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>$ clang -v
clang version 3.5.0 (203643)
Target: x86_64-unknown-linux-gnu
$ cat vptr.cc
struct X {
virtual void foo();
};
void foo(X *x) {
x->foo();
}
void bar(X *x, void (X::*fn)()) {
(x->*fn)();
}
$ clang++ vptr.cc -O1 -S -emit-llvm
$ cat vptr.ll
; ModuleID = '/tmp/vptr.cc'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
%struct.X = type { i32 (...)** }
; Function Attrs: uwtable
define void @_Z3fooP1X(%struct.X* %x) #0 {
%1 = bitcast %struct.X* %x to void (%struct.X*)***
%2 = load void (%struct.X*)*** %1, align 8, !tbaa !1
%3 = load void (%struct.X*)** %2, align 8
tail call void %3(%struct.X* %x)
ret void
}
; Function Attrs: uwtable
define void @_Z3barP1XMS_FvvE(%struct.X* %x, i64 %fn.coerce0, i64 %fn.coerce1)
#0 {
%1 = bitcast %struct.X* %x to i8*
%2 = getelementptr inbounds i8* %1, i64 %fn.coerce1
%3 = bitcast i8* %2 to %struct.X*
%4 = and i64 %fn.coerce0, 1
%5 = icmp eq i64 %4, 0
br i1 %5, label %13, label %6
; <label>:6 ; preds = %0
%7 = bitcast i8* %2 to i8**
%8 = load i8** %7, align 8
%9 = add i64 %fn.coerce0, -1
%10 = getelementptr i8* %8, i64 %9
%11 = bitcast i8* %10 to void (%struct.X*)**
%12 = load void (%struct.X*)** %11, align 8
br label %15
; <label>:13 ; preds = %0
%14 = inttoptr i64 %fn.coerce0 to void (%struct.X*)*
br label %15
; <label>:15 ; preds = %13, %6
%16 = phi void (%struct.X*)* [ %12, %6 ], [ %14, %13 ]
tail call void %16(%struct.X* %3)
ret void
}
attributes #0 = { uwtable "less-precise-fpmad"="false"
"no-frame-pointer-elim"="false" "no-infs-fp-math"="false"
"no-nans-fp-math"="false" "stack-protector-buffer-size"="8"
"unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.ident = !{!0}
!0 = metadata !{metadata !"clang version 3.5.0 (203643)"}
!1 = metadata !{metadata !2, metadata !2, i64 0}
!2 = metadata !{metadata !"vtable pointer", metadata !3, i64 0}
!3 = metadata !{metadata !"Simple C/C++ TBAA"}
============================================================
vptr load in foo() is marked with !tbaa !1
vptr load in bar() (%12 = load void (%struct.X*)** %11, align 8) is not marked
with !tbaa !1
This breaks ThreadSanitizer instrumentation pass, and leads to worse race
reports.</pre>
</div>
</p>
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