Revert r170020, "Simplify negated bit test", for now.

This assumes (1 << n) is always not zero. Consider n is greater than word size.
Although I know it is undefined, this transforms undefined behavior hidden.

This led clang unexpected behavior with some failures. I will investigate to fix undefined shl in clang.

llvm-svn: 170128

1 files changed, 0 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 00807a391a9..1b96c3cca4e 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2034,15 +2034,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
                                                CI->countTrailingZeros()));
       }
 
-      // Turn x&~y == 0 into x&y != 0 if x is a power of 2.
-      Value *X = 0, *Y = 0;
-      if (match(Op0, m_And(m_Value(X), m_Not(m_Value(Y)))) &&
-          match(Op1, m_Zero()) && isKnownToBeAPowerOfTwo(X, TD)) {
-        return new ICmpInst(ICmpInst::ICMP_NE,
-                            Builder->CreateAnd(X, Y),
-                            Op1);
-      }
-
       break;
     }
     case ICmpInst::ICMP_NE: {
@@ -2080,15 +2071,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
                                                CI->countTrailingZeros()));
       }
 
-      // Turn x&~y != 0 into x&y == 0 if x is a power of 2.
-      Value *X = 0, *Y = 0;
-      if (match(Op0, m_And(m_Value(X), m_Not(m_Value(Y)))) &&
-          match(Op1, m_Zero()) && isKnownToBeAPowerOfTwo(X, TD)) {
-        return new ICmpInst(ICmpInst::ICMP_EQ,
-                            Builder->CreateAnd(X, Y),
-                            Op1);
-      }
-
       break;
     }
     case ICmpInst::ICMP_ULT: