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Layout the code for trapping arithmetic so that the overflow case comes after 

the normal case.

Before, for this:

$ cat t.c
int test(int x) { return x * 2; }

We would get this:

   addl  %edi, %edi
   jno   LBB0_2
## BB#1:                                ## %overflow
   ud2
LBB0_2:                                 ## %nooverflow
   movl    %edi, %eax
   popq    %rbp
   ret

Now we get this:

   addl   %edi, %edi
   jo     LBB0_2
## BB#1:                                ## %nooverflow
   movl                                 %edi, %eax
   popq                                 %rbp
   ret
LBB0_2:                                 ## %overflow
   ud2

<rdar://problem/8283919>

llvm-svn: 134642
This commit is contained in:
Bill Wendling 2011-07-07 21:13:10 +00:00
parent 13bcc6c1c7
commit e367f387af
1 changed files with 10 additions and 4 deletions
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14
clang/lib/CodeGen/CGExprScalar.cpp
View File

@ -1677,9 +1677,11 @@ Value *ScalarExprEmitter::EmitCompoundAssign(const CompoundAssignOperator *E,
void ScalarExprEmitter::EmitUndefinedBehaviorIntegerDivAndRemCheck(
const BinOpInfo &Ops,
llvm::Value *Zero, bool isDiv) {
llvm::BasicBlock *overflowBB = CGF.createBasicBlock("overflow", CGF.CurFn);
llvm::Function::iterator insertPt = Builder.GetInsertBlock();
llvm::BasicBlock *contBB =
CGF.createBasicBlock(isDiv ? "div.cont" : "rem.cont", CGF.CurFn);
CGF.createBasicBlock(isDiv ? "div.cont" : "rem.cont", CGF.CurFn,
llvm::next(insertPt));
llvm::BasicBlock *overflowBB = CGF.createBasicBlock("overflow", CGF.CurFn);
const llvm::IntegerType *Ty = cast<llvm::IntegerType>(Zero->getType());
@ -1709,9 +1711,11 @@ Value *ScalarExprEmitter::EmitDiv(const BinOpInfo &Ops) {
if (Ops.Ty->isIntegerType())
EmitUndefinedBehaviorIntegerDivAndRemCheck(Ops, Zero, true);
else if (Ops.Ty->isRealFloatingType()) {
llvm::Function::iterator insertPt = Builder.GetInsertBlock();
llvm::BasicBlock *DivCont = CGF.createBasicBlock("div.cont", CGF.CurFn,
llvm::next(insertPt));
llvm::BasicBlock *overflowBB = CGF.createBasicBlock("overflow",
CGF.CurFn);
llvm::BasicBlock *DivCont = CGF.createBasicBlock("div.cont", CGF.CurFn);
CGF.Builder.CreateCondBr(Builder.CreateFCmpOEQ(Ops.RHS, Zero),
overflowBB, DivCont);
EmitOverflowBB(overflowBB);
@ -1778,8 +1782,10 @@ Value *ScalarExprEmitter::EmitOverflowCheckedBinOp(const BinOpInfo &Ops) {
// Branch in case of overflow.
llvm::BasicBlock *initialBB = Builder.GetInsertBlock();
llvm::Function::iterator insertPt = initialBB;
llvm::BasicBlock *continueBB = CGF.createBasicBlock("nooverflow", CGF.CurFn,
llvm::next(insertPt));
llvm::BasicBlock *overflowBB = CGF.createBasicBlock("overflow", CGF.CurFn);
llvm::BasicBlock *continueBB = CGF.createBasicBlock("nooverflow", CGF.CurFn);
Builder.CreateCondBr(overflow, overflowBB, continueBB);