From: Chris Lattner <sabre@nondot.org>
Date: Sat, 7 Aug 2010 00:20:46 +0000 (+0000)
Subject: Correct -ftrapv to trap on errors, instead of calling the
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=93a00357f2795404c6709d9e06b4f717c82e6efb;p=clang

Correct -ftrapv to trap on errors, instead of calling the
__overflow_handler entrypoint that David Chisnall made up.
Calling __overflow_handler is not part of the contract of
-ftrapv provided by GCC, and should never have been checked
in in the first place.

According to:
http://permalink.gmane.org/gmane.comp.compilers.clang.devel/8699

David is using this for some of arbitrary precision integer stuff
or something, which is not an appropriate thing to implement on
this.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@110490 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index ae073da672..d2ff5623cb 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -1548,54 +1548,21 @@ Value *ScalarExprEmitter::EmitOverflowCheckedBinOp(const BinOpInfo &Ops) {
   Value *overflow = Builder.CreateExtractValue(resultAndOverflow, 1);
 
   // Branch in case of overflow.
-  llvm::BasicBlock *initialBB = Builder.GetInsertBlock();
-  llvm::BasicBlock *overflowBB =
-    CGF.createBasicBlock("overflow", CGF.CurFn);
-  llvm::BasicBlock *continueBB =
-    CGF.createBasicBlock("overflow.continue", CGF.CurFn);
+  llvm::BasicBlock *overflowBB = CGF.createBasicBlock("overflow", CGF.CurFn);
+  llvm::BasicBlock *continueBB = CGF.createBasicBlock("nooverflow", CGF.CurFn);
 
   Builder.CreateCondBr(overflow, overflowBB, continueBB);
 
-  // Handle overflow
-
+  // Handle overflow with llvm.trap.
+  // TODO: it would be better to generate one of these blocks per function.
   Builder.SetInsertPoint(overflowBB);
-
-  // Handler is:
-  // long long *__overflow_handler)(long long a, long long b, char op,
-  // char width)
-  std::vector<const llvm::Type*> handerArgTypes;
-  handerArgTypes.push_back(CGF.Int64Ty);
-  handerArgTypes.push_back(CGF.Int64Ty);
-  handerArgTypes.push_back(llvm::Type::getInt8Ty(VMContext));
-  handerArgTypes.push_back(llvm::Type::getInt8Ty(VMContext));
-  llvm::FunctionType *handlerTy =
-    llvm::FunctionType::get(CGF.Int64Ty, handerArgTypes, false);
-  llvm::Value *handlerFunction =
-    CGF.CGM.getModule().getOrInsertGlobal("__overflow_handler",
-        llvm::PointerType::getUnqual(handlerTy));
-  handlerFunction = Builder.CreateLoad(handlerFunction);
-
-  llvm::Value *lhs = Builder.CreateSExt(Ops.LHS, CGF.Int64Ty);
-  llvm::Value *rhs = Builder.CreateSExt(Ops.RHS, CGF.Int64Ty);
-
-  llvm::Value *handlerResult =
-    Builder.CreateCall4(handlerFunction, lhs, rhs,
-                        Builder.getInt8(OpID),
-              Builder.getInt8(cast<llvm::IntegerType>(opTy)->getBitWidth()));
-
-  handlerResult = Builder.CreateTrunc(handlerResult, opTy);
-
-  Builder.CreateBr(continueBB);
-
-  // Set up the continuation
+  llvm::Function *Trap = CGF.CGM.getIntrinsic(llvm::Intrinsic::trap);
+  Builder.CreateCall(Trap);
+  Builder.CreateUnreachable();
+  
+  // Continue on.
   Builder.SetInsertPoint(continueBB);
-  // Get the correct result
-  llvm::PHINode *phi = Builder.CreatePHI(opTy);
-  phi->reserveOperandSpace(2);
-  phi->addIncoming(result, initialBB);
-  phi->addIncoming(handlerResult, overflowBB);
-
-  return phi;
+  return result;
 }
 
 Value *ScalarExprEmitter::EmitAdd(const BinOpInfo &Ops) {
diff --git a/test/CodeGen/trapv.c b/test/CodeGen/trapv.c
index 46b1c8b14f..7f192c634c 100644
--- a/test/CodeGen/trapv.c
+++ b/test/CodeGen/trapv.c
@@ -20,14 +20,7 @@ void test0() {
   // CHECK-NEXT: [[T4:%.*]] = extractvalue [[I32O]] [[T3]], 0
   // CHECK-NEXT: [[T5:%.*]] = extractvalue [[I32O]] [[T3]], 1
   // CHECK-NEXT: br i1 [[T5]]
-  // CHECK:      [[F:%.*]] = load i64 (i64, i64, i8, i8)** @__overflow_handler
-  // CHECK-NEXT: [[T6:%.*]] = sext i32 [[T1]] to i64
-  // CHECK-NEXT: [[T7:%.*]] = sext i32 [[T2]] to i64
-  // CHECK-NEXT: [[T8:%.*]] = call i64 [[F]](i64 [[T6]], i64 [[T7]], i8 3, i8 32)
-  // CHECK-NEXT: [[T9:%.*]] = trunc i64 [[T8]] to i32
-  // CHECK-NEXT: br label
-  // CHECK:      [[T10:%.*]] = phi i32 [ [[T4]], {{.*}} ], [ [[T9]], {{.*}} ]
-  // CHECK-NEXT: store i32 [[T10]], i32* @i
+  // CHECK:      call void @llvm.trap()
   i = j + k;
 }
 
@@ -41,14 +34,7 @@ void test1() {
   // CHECK-NEXT: [[T3:%.*]] = extractvalue [[I32O]] [[T2]], 0
   // CHECK-NEXT: [[T4:%.*]] = extractvalue [[I32O]] [[T2]], 1
   // CHECK-NEXT: br i1 [[T4]]
-  // CHECK:      [[F:%.*]] = load i64 (i64, i64, i8, i8)** @__overflow_handler
-  // CHECK-NEXT: [[T5:%.*]] = sext i32 [[T1]] to i64
-  // CHECK-NEXT: [[T6:%.*]] = call i64 [[F]](i64 [[T5]], i64 1, i8 3, i8 32)
-  // CHECK-NEXT: [[T7:%.*]] = trunc i64 [[T6]] to i32
-  // CHECK-NEXT: br label
-  // CHECK:      [[T8:%.*]] = phi i32 [ [[T3]], {{.*}} ], [ [[T7]], {{.*}} ]
-  // CHECK-NEXT: store i32 [[T8]], i32* @i
-  // CHECK-NEXT: call void @opaque(i32 [[T1]])
+  // CHECK:      call void @llvm.trap()
 }
 
 // CHECK: define void @test2()
@@ -61,12 +47,5 @@ void test2() {
   // CHECK-NEXT: [[T3:%.*]] = extractvalue [[I32O]] [[T2]], 0
   // CHECK-NEXT: [[T4:%.*]] = extractvalue [[I32O]] [[T2]], 1
   // CHECK-NEXT: br i1 [[T4]]
-  // CHECK:      [[F:%.*]] = load i64 (i64, i64, i8, i8)** @__overflow_handler
-  // CHECK-NEXT: [[T5:%.*]] = sext i32 [[T1]] to i64
-  // CHECK-NEXT: [[T6:%.*]] = call i64 [[F]](i64 [[T5]], i64 1, i8 3, i8 32)
-  // CHECK-NEXT: [[T7:%.*]] = trunc i64 [[T6]] to i32
-  // CHECK-NEXT: br label
-  // CHECK:      [[T8:%.*]] = phi i32 [ [[T3]], {{.*}} ], [ [[T7]], {{.*}} ]
-  // CHECK-NEXT: store i32 [[T8]], i32* @i
-  // CHECK-NEXT: call void @opaque(i32 [[T8]])
+  // CHECK:      call void @llvm.trap()
 }