[CodeGenCXX] Emit strip.invariant.group with -fstrict-vtable-pointers
Summary:
Emmiting new intrinsic that strips invariant.groups to make
devirtulization sound, as described in RFC: Devirtualization v2.
Reviewers: rjmccall, rsmith, amharc, kuhar
Subscribers: llvm-commits, cfe-commits
Differential Revision: https://reviews.llvm.org/D47299
Co-authored-by: Krzysztof Pszeniczny <krzysztof.pszeniczny@gmail.com>
llvm-svn: 336137
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 12b3093..3097caa 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -3870,6 +3870,18 @@
}
Address addr = base.getAddress();
+ if (auto *ClassDef = dyn_cast<CXXRecordDecl>(rec)) {
+ if (CGM.getCodeGenOpts().StrictVTablePointers &&
+ ClassDef->isDynamicClass()) {
+ // Getting to any field of dynamic object requires stripping dynamic
+ // information provided by invariant.group. This is because accessing
+ // fields may leak the real address of dynamic object, which could result
+ // in miscompilation when leaked pointer would be compared.
+ auto *stripped = Builder.CreateStripInvariantGroup(addr.getPointer());
+ addr = Address(stripped, addr.getAlignment());
+ }
+ }
+
unsigned RecordCVR = base.getVRQualifiers();
if (rec->isUnion()) {
// For unions, there is no pointer adjustment.