[llvm] e894511 - [InstCombine] Remove redundant unsigned underflow fold (NFCI)

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-04-25T14:22:43+02:00
New Revision: e8945110d238289886cc51cafe9461bfcf109f6f

URL: https://github.com/llvm/llvm-project/commit/e8945110d238289886cc51cafe9461bfcf109f6f
DIFF: https://github.com/llvm/llvm-project/commit/e8945110d238289886cc51cafe9461bfcf109f6f.diff

LOG: [InstCombine] Remove redundant unsigned underflow fold (NFCI)

This is now handled as a combination of two other folds:
(A+B) <= A & (A+B) != 0  -->  (A+B)-1 < A
(A+B)-1 < A  -->  -B < A

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

Removed: 
    


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diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 4a97d6b83767b..8c25d4992f736 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -991,22 +991,13 @@ static Value *foldUnsignedUnderflowCheck(ICmpInst *ZeroICmp,
     };
 
     // Given  ZeroCmpOp = (A + B)
-    //   ZeroCmpOp <= A && ZeroCmpOp != 0  -->  (0-B) <  A
-    //   ZeroCmpOp >  A || ZeroCmpOp == 0  -->  (0-B) >= A
-    //
     //   ZeroCmpOp <  A && ZeroCmpOp != 0  -->  (0-X) <  Y  iff
     //   ZeroCmpOp >= A || ZeroCmpOp == 0  -->  (0-X) >= Y  iff
     //     with X being the value (A/B) that is known to be non-zero,
     //     and Y being remaining value.
-    if (UnsignedPred == ICmpInst::ICMP_ULE && EqPred == ICmpInst::ICMP_NE &&
-        IsAnd)
-      return Builder.CreateICmpULT(Builder.CreateNeg(B), A);
     if (UnsignedPred == ICmpInst::ICMP_ULT && EqPred == ICmpInst::ICMP_NE &&
         IsAnd && GetKnownNonZeroAndOther(B, A))
       return Builder.CreateICmpULT(Builder.CreateNeg(B), A);
-    if (UnsignedPred == ICmpInst::ICMP_UGT && EqPred == ICmpInst::ICMP_EQ &&
-        !IsAnd)
-      return Builder.CreateICmpUGE(Builder.CreateNeg(B), A);
     if (UnsignedPred == ICmpInst::ICMP_UGE && EqPred == ICmpInst::ICMP_EQ &&
         !IsAnd && GetKnownNonZeroAndOther(B, A))
       return Builder.CreateICmpUGE(Builder.CreateNeg(B), A);