generalize the sadd creation code to not require that the
sadd formed is half the size of the original type. We can
now compile this into a sadd.i8:
unsigned char X(char a, char b) {
int res = a+b;
if ((unsigned )(res+128) > 255U)
abort();
return res;
}
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122178 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 1142686..9f0fa3e 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1635,54 +1635,31 @@
TI->getType()->getPrimitiveSizeInBits() > NewWidth) return 0;
}
- const IntegerType *WideType = cast<IntegerType>(CI1->getType());
- unsigned WideWidth = WideType->getBitWidth();
- unsigned NarrowWidth = WideWidth / 2;
- const IntegerType *NarrowType =
- IntegerType::get(CI1->getContext(), NarrowWidth);
-
- // NarrowAllOnes and NarrowSignBit are the magic constants used to
- // perform an overflow check in the wider type: 0x00..00FF..FF and
- // 0x00..0010..00 respectively, where the highest set bit in each is
- // what would be the sign bit in the narrower type.
- ConstantInt *NarrowAllOnes = cast<ConstantInt>(ConstantInt::get(WideType,
- APInt::getAllOnesValue(NarrowWidth).zext(WideWidth)));
- APInt SignBit(WideWidth, 0);
- SignBit.setBit(NarrowWidth-1);
- ConstantInt *NarrowSignBit =
- cast<ConstantInt>(ConstantInt::get(WideType, SignBit));
-
- if (CI1 != NarrowAllOnes || CI2 != NarrowSignBit)
- return 0;
-
- Module *M = I.getParent()->getParent()->getParent();
-
- const Type *IntrinsicType = NarrowType;
- Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow,
- &IntrinsicType, 1);
-
- BasicBlock *InitialBlock = Builder->GetInsertBlock();
- BasicBlock::iterator InitialInsert = Builder->GetInsertPoint();
-
// If the pattern matches, truncate the inputs to the narrower type and
// use the sadd_with_overflow intrinsic to efficiently compute both the
// result and the overflow bit.
- Builder->SetInsertPoint(OrigAdd->getParent(),
- BasicBlock::iterator(OrigAdd));
+ Module *M = I.getParent()->getParent()->getParent();
- Value *TruncA = Builder->CreateTrunc(A, NarrowType, A->getName());
- Value *TruncB = Builder->CreateTrunc(B, NarrowType, B->getName());
- CallInst *Call = Builder->CreateCall2(F, TruncA, TruncB);
- Value *Add = Builder->CreateExtractValue(Call, 0);
- Value *ZExt = Builder->CreateZExt(Add, WideType);
+ const Type *NewType = IntegerType::get(OrigAdd->getContext(), NewWidth);
+ Value *F = Intrinsic::getDeclaration(M, Intrinsic::sadd_with_overflow,
+ &NewType, 1);
+
+ // Put the new code above the original add, in case there are any uses of the
+ // add between the add and the compare.
+ Builder->SetInsertPoint(OrigAdd->getParent(), BasicBlock::iterator(OrigAdd));
+
+ Value *TruncA = Builder->CreateTrunc(A, NewType, A->getName()+".trunc");
+ Value *TruncB = Builder->CreateTrunc(B, NewType, B->getName()+".trunc");
+ CallInst *Call = Builder->CreateCall2(F, TruncA, TruncB, "sadd");
+ Value *Add = Builder->CreateExtractValue(Call, 0, "sadd.result");
+ Value *ZExt = Builder->CreateZExt(Add, OrigAdd->getType());
// The inner add was the result of the narrow add, zero extended to the
// wider type. Replace it with the result computed by the intrinsic.
OrigAdd->replaceAllUsesWith(ZExt);
- Builder->SetInsertPoint(InitialBlock, InitialInsert);
-
- return ExtractValueInst::Create(Call, 1);
+ // The original icmp gets replaced with the overflow value.
+ return ExtractValueInst::Create(Call, 1, "sadd.overflow");
}