Revert "[InstCombine] fold zext of masked bit set/clear"

This reverts commit a041c4ec6f7aa659b235cb67e9231a05e0a33b7d.

This looks like a non-trivial change and there has been no code
reviews (at least there were no phabricator revisions attached to the
commit description). It is also causing a regression in one of our
downstream integration tests, we haven't been able to come up with a
minimal reproducer yet.

1 files changed, 3 insertions, 17 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index b9be41840ff..3ba56bbe53e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -922,24 +922,10 @@ Instruction *InstCombiner::transformZExtICmp(ICmpInst *Cmp, ZExtInst &Zext,
     }
   }
 
+  // icmp ne A, B is equal to xor A, B when A and B only really have one bit.
+  // It is also profitable to transform icmp eq into not(xor(A, B)) because that
+  // may lead to additional simplifications.
   if (Cmp->isEquality() && Zext.getType() == Cmp->getOperand(0)->getType()) {
-    // Test if a bit is clear/set using a shifted-one mask:
-    // zext (icmp eq (and X, (1 << ShAmt)), 0) --> and (lshr (not X), ShAmt), 1
-    // zext (icmp ne (and X, (1 << ShAmt)), 0) --> and (lshr X, ShAmt), 1
-    Value *X, *ShAmt;
-    if (Cmp->hasOneUse() && match(Cmp->getOperand(1), m_ZeroInt()) &&
-        match(Cmp->getOperand(0),
-              m_OneUse(m_c_And(m_Shl(m_One(), m_Value(ShAmt)), m_Value(X))))) {
-      if (Cmp->getPredicate() == ICmpInst::ICMP_EQ)
-        X = Builder.CreateNot(X);
-      Value *Lshr = Builder.CreateLShr(X, ShAmt);
-      Value *And1 = Builder.CreateAnd(Lshr, ConstantInt::get(X->getType(), 1));
-      return replaceInstUsesWith(Zext, And1);
-    }
-
-    // icmp ne A, B is equal to xor A, B when A and B only really have one bit.
-    // It is also profitable to transform icmp eq into not(xor(A, B)) because
-    // that may lead to additional simplifications.
     if (IntegerType *ITy = dyn_cast<IntegerType>(Zext.getType())) {
       Value *LHS = Cmp->getOperand(0);
       Value *RHS = Cmp->getOperand(1);