From: Craig Topper <craig.topper@gmail.com>
Date: Thu, 23 Mar 2017 21:00:13 +0000 (+0000)
Subject: [InstCombine] Remove some code from visitAnd that dealt with trying to reduce the... 
X-Git-Tag: llvmorg-5.0.0-rc1~9305
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=74494d017998436694da3ebc8af7cf7772d8cb48;p=platform%2Fupstream%2Fllvm.git

[InstCombine] Remove some code from visitAnd that dealt with trying to reduce the LHS of a sub to 0. This should now be fully handled by SimplifyDemandedInstructionBits now.

Now that we call ShrinkDemandedConstant on the RHS of sub this should be taken care of. This code doesn't trigger on any in tree regressions, but did before ShrinkDemandedConstant was added to the RHS.

llvm-svn: 298644
---

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index b06bb1b..13f3f31 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -1335,18 +1335,6 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
         if (AndRHSMask == 1 && match(Op0LHS, m_Zero()))
           return BinaryOperator::CreateAnd(Op0RHS, AndRHS);
 
-        // (A - N) & AndRHS -> -N & AndRHS iff A&AndRHS==0 and AndRHS
-        // has 1's for all bits that the subtraction with A might affect.
-        if (Op0I->hasOneUse() && !match(Op0LHS, m_Zero())) {
-          uint32_t BitWidth = AndRHSMask.getBitWidth();
-          uint32_t Zeros = AndRHSMask.countLeadingZeros();
-          APInt Mask = APInt::getLowBitsSet(BitWidth, BitWidth - Zeros);
-
-          if (MaskedValueIsZero(Op0LHS, Mask, 0, &I)) {
-            Value *NewNeg = Builder->CreateNeg(Op0RHS);
-            return BinaryOperator::CreateAnd(NewNeg, AndRHS);
-          }
-        }
         break;
 
       case Instruction::Shl: