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[PR26550] Use a different TBAA root for C++ vs C. 

This commit changes the root from "Simple C/C++ TBAA" to "Simple C++ TBAA" for
C++.

The problem is that the type name in the TBAA nodes is generated differently
for C vs C++. If we link an IR file for C with an IR file for C++, since they
have the same root and the type names are different, accesses to the two type
nodes will be considered no-alias, even though the two type nodes are from
the same type in a header file.

The fix is to use different roots for C and C++. Types from C will be treated
conservatively in respect to types from C++.

Follow-up commits will change the C root to "Simple C TBAA" plus some mangling
change for C types to make it a little more aggresive.

llvm-svn: 260567
This commit is contained in:
Manman Ren 2016-02-11 19:19:18 +00:00
parent bde158cbc7
commit 37dec10dbc
4 changed files with 9 additions and 5 deletions
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8
clang/lib/CodeGen/CodeGenTBAA.cpp
View File

@ -44,8 +44,12 @@ llvm::MDNode *CodeGenTBAA::getRoot() {
// if our LLVM IR is linked with LLVM IR from a different front-end
// (or a different version of this front-end), their TBAA trees will
// remain distinct, and the optimizer will treat them conservatively.
if (!Root)
Root = MDHelper.createTBAARoot("Simple C/C++ TBAA");
if (!Root) {
if (Features.CPlusPlus)
Root = MDHelper.createTBAARoot("Simple C++ TBAA");
else
Root = MDHelper.createTBAARoot("Simple C/C++ TBAA");
}
return Root;
}

2
clang/test/CodeGen/tbaa-class.cpp
View File

@ -199,7 +199,7 @@ uint32_t g12(StructC *C, StructD *D, uint64_t count) {
}
// CHECK: [[TYPE_char:!.*]] = !{!"omnipotent char", [[TAG_cxx_tbaa:!.*]],
// CHECK: [[TAG_cxx_tbaa]] = !{!"Simple C/C++ TBAA"}
// CHECK: [[TAG_cxx_tbaa]] = !{!"Simple C++ TBAA"}
// CHECK: [[TAG_i32]] = !{[[TYPE_i32:!.*]], [[TYPE_i32]], i64 0}
// CHECK: [[TYPE_i32]] = !{!"int", [[TYPE_char]],
// CHECK: [[TAG_i16]] = !{[[TYPE_i16:!.*]], [[TYPE_i16]], i64 0}

2
clang/test/CodeGen/tbaa-for-vptr.cpp
View File

@ -32,4 +32,4 @@ void CallFoo(A *a, int (A::*fp)() const) {
//
// CHECK: [[NUM]] = !{[[TYPE:!.*]], [[TYPE]], i64 0}
// CHECK: [[TYPE]] = !{!"vtable pointer", !{{.*}}
// NOTBAA-NOT: = !{!"Simple C/C++ TBAA"}
// NOTBAA-NOT: = !{!"Simple C++ TBAA"}

2
clang/test/CodeGen/tbaa.cpp
View File

@ -237,7 +237,7 @@ uint32_t g15(StructS *S, StructS3 *S3, uint64_t count) {
}
// CHECK: [[TYPE_char:!.*]] = !{!"omnipotent char", [[TAG_cxx_tbaa:!.*]],
// CHECK: [[TAG_cxx_tbaa]] = !{!"Simple C/C++ TBAA"}
// CHECK: [[TAG_cxx_tbaa]] = !{!"Simple C++ TBAA"}
// CHECK: [[TAG_i32]] = !{[[TYPE_i32:!.*]], [[TYPE_i32]], i64 0}
// CHECK: [[TYPE_i32]] = !{!"int", [[TYPE_char]],
// CHECK: [[TAG_i16]] = !{[[TYPE_i16:!.*]], [[TYPE_i16]], i64 0}