[PATCH] D112298: [InstCombine] Generalize sadd.sat combine to compute sign bits.

[Dave Green via Phabricator via llvm-commits]

dmgreen added inline comments.


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Comment at: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp:2324-2325
   Function *F = Intrinsic::getDeclaration(MinMax1.getModule(), IntrinsicID, NewTy);
-  Value *AT = Builder.CreateSExt(A, NewTy);
-  Value *BT = Builder.CreateSExt(B, NewTy);
+  Value *AT = Builder.CreateTrunc(AddSub->getOperand(0), NewTy);
+  Value *BT = Builder.CreateTrunc(AddSub->getOperand(1), NewTy);
   Value *Sat = Builder.CreateCall(F, {AT, BT});
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lebedev.ri wrote:
> Should these not be `CreateTruncOrBitCast`?
I think CreateTrunc works how you imagine CreateTruncOrBitCast works, if everything is an integer type. It starts out with `if (V->getType() == DestTy) return V;`


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D112298/new/

https://reviews.llvm.org/D112298