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List:       cfe-commits
Subject:    r243206 - [CodeGen] Don't UBSan-ize the argument to __builtin_frame_address
From:       David Majnemer <david.majnemer () gmail ! com>
Date:       2015-07-25 5:57:24
Message-ID: 20150725055724.D856E1BE001 () llvm ! org
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Author: majnemer
Date: Sat Jul 25 00:57:24 2015
New Revision: 243206

URL: http://llvm.org/viewvc/llvm-project?rev=243206&view=rev
Log:
[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.

Modified:
    cfe/trunk/lib/CodeGen/CGBuiltin.cpp
    cfe/trunk/test/CodeGen/integer-overflow.c

Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGBuiltin.cpp?rev=243206&r1=243205&r2=243206&view=diff
 ==============================================================================
--- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Sat Jul 25 00:57:24 2015
@@ -866,14 +866,14 @@ RValue CodeGenFunction::EmitBuiltinExpr(
                                       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));
   }

Modified: cfe/trunk/test/CodeGen/integer-overflow.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/integer-overflow.c?rev=243206&r1=243205&r2=243206&view=diff
 ==============================================================================
--- cfe/trunk/test/CodeGen/integer-overflow.c (original)
+++ cfe/trunk/test/CodeGen/integer-overflow.c Sat Jul 25 00:57:24 2015
@@ -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)
 }


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