[Clang] Add __builtin_launder
Summary:
This patch adds `__builtin_launder`, which is required to implement `std::launder`. Additionally GCC provides `__builtin_launder`, so thing brings Clang in-line with GCC.
I'm not exactly sure what magic `__builtin_launder` requires, but based on previous discussions this patch applies a `@llvm.invariant.group.barrier`. As noted in previous discussions, this may not be enough to correctly handle vtables.
Reviewers: rnk, majnemer, rsmith
Reviewed By: rsmith
Subscribers: kristina, Romain-Geissler-1A, erichkeane, amharc, jroelofs, cfe-commits, Prazek
Differential Revision: https://reviews.llvm.org/D40218
llvm-svn: 349195
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index f1df983..eea9207a 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -25,6 +25,7 @@
#include "clang/Basic/TargetBuiltins.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/CodeGen/CGFunctionInfo.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DataLayout.h"
@@ -1409,6 +1410,42 @@
return Res;
}
+static bool
+TypeRequiresBuiltinLaunderImp(const ASTContext &Ctx, QualType Ty,
+ llvm::SmallPtrSetImpl<const Decl *> &Seen) {
+ if (const auto *Arr = Ctx.getAsArrayType(Ty))
+ Ty = Ctx.getBaseElementType(Arr);
+
+ const auto *Record = Ty->getAsCXXRecordDecl();
+ if (!Record)
+ return false;
+
+ // We've already checked this type, or are in the process of checking it.
+ if (!Seen.insert(Record).second)
+ return false;
+
+ assert(Record->hasDefinition() &&
+ "Incomplete types should already be diagnosed");
+
+ if (Record->isDynamicClass())
+ return true;
+
+ for (FieldDecl *F : Record->fields()) {
+ if (TypeRequiresBuiltinLaunderImp(Ctx, F->getType(), Seen))
+ return true;
+ }
+ return false;
+}
+
+/// Determine if the specified type requires laundering by checking if it is a
+/// dynamic class type or contains a subobject which is a dynamic class type.
+static bool TypeRequiresBuiltinLaunder(CodeGenModule &CGM, QualType Ty) {
+ if (!CGM.getCodeGenOpts().StrictVTablePointers)
+ return false;
+ llvm::SmallPtrSet<const Decl *, 16> Seen;
+ return TypeRequiresBuiltinLaunderImp(CGM.getContext(), Ty, Seen);
+}
+
RValue CodeGenFunction::emitRotate(const CallExpr *E, bool IsRotateRight) {
llvm::Value *Src = EmitScalarExpr(E->getArg(0));
llvm::Value *ShiftAmt = EmitScalarExpr(E->getArg(1));
@@ -2474,6 +2511,15 @@
return RValue::get(nullptr);
}
+ case Builtin::BI__builtin_launder: {
+ const Expr *Arg = E->getArg(0);
+ QualType ArgTy = Arg->getType()->getPointeeType();
+ Value *Ptr = EmitScalarExpr(Arg);
+ if (TypeRequiresBuiltinLaunder(CGM, ArgTy))
+ Ptr = Builder.CreateLaunderInvariantGroup(Ptr);
+
+ return RValue::get(Ptr);
+ }
case Builtin::BI__sync_fetch_and_add:
case Builtin::BI__sync_fetch_and_sub:
case Builtin::BI__sync_fetch_and_or: