[CodeGen] Don't UBSan-ize the argument to __builtin_frame_address

__builtin_frame_address requires its argument to be a constant
expression which already implies that it cannot have undefined behavior.
However, we used EmitScalarExpr to emit the argument causing UBSan to
try to check for overflow.

Instead, use the constant expression emission system.

This fixes PR24256.

llvm-svn: 243206

2 files changed, 11 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 463b3eee3d3..9b8694f9c5f 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -866,14 +866,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
                                       llvm::ConstantInt::get(Int32Ty, Offset)));
   }
   case Builtin::BI__builtin_return_address: {
-    Value *Depth = EmitScalarExpr(E->getArg(0));
-    Depth = Builder.CreateIntCast(Depth, Int32Ty, false);
+    Value *Depth =
+        CGM.EmitConstantExpr(E->getArg(0), getContext().UnsignedIntTy, this);
     Value *F = CGM.getIntrinsic(Intrinsic::returnaddress);
     return RValue::get(Builder.CreateCall(F, Depth));
   }
   case Builtin::BI__builtin_frame_address: {
-    Value *Depth = EmitScalarExpr(E->getArg(0));
-    Depth = Builder.CreateIntCast(Depth, Int32Ty, false);
+    Value *Depth =
+        CGM.EmitConstantExpr(E->getArg(0), getContext().UnsignedIntTy, this);
     Value *F = CGM.getIntrinsic(Intrinsic::frameaddress);
     return RValue::get(Builder.CreateCall(F, Depth));
   }
diff --git a/clang/test/CodeGen/integer-overflow.c b/clang/test/CodeGen/integer-overflow.c
index de3b53f4b5b..6a7c3e51ee1 100644
--- a/clang/test/CodeGen/integer-overflow.c
+++ b/clang/test/CodeGen/integer-overflow.c
@@ -72,4 +72,11 @@ void test1() {
   // TRAPV: add i8 {{.*}}, 1
   // CATCH_UB: add i8 {{.*}}, 1
   ++PR9350;
+
+  // PR24256: don't instrument __builtin_frame_address.
+  __builtin_frame_address(0 + 0);
+  // DEFAULT:  call i8* @llvm.frameaddress(i32 0)
+  // WRAPV:    call i8* @llvm.frameaddress(i32 0)
+  // TRAPV:    call i8* @llvm.frameaddress(i32 0)
+  // CATCH_UB: call i8* @llvm.frameaddress(i32 0)
 }