From 38d2b2442feaa777cf87c5f57939b158f04735fe Mon Sep 17 00:00:00 2001
From: NAKAMURA Takumi <geek4civic@gmail.com>
Date: Thu, 13 Dec 2012 14:28:16 +0000
Subject: [PATCH] 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
---
 .../Transforms/InstCombine/InstCombineCompares.cpp | 18 ---------------
 llvm/test/Transforms/InstCombine/icmp.ll           | 26 ----------------------
 2 files changed, 44 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 00807a3..1b96c3c 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:
diff --git a/llvm/test/Transforms/InstCombine/icmp.ll b/llvm/test/Transforms/InstCombine/icmp.ll
index d11b6cc..8e064a4 100644
--- a/llvm/test/Transforms/InstCombine/icmp.ll
+++ b/llvm/test/Transforms/InstCombine/icmp.ll
@@ -677,29 +677,3 @@ define i1 @test66(i64 %A, i64 %B) {
 ; CHECK-NEXT: ret i1 true
   ret i1 %cmp
 }
-
-define i1 @test67(i32 %A, i32 %B) {
-  %neg = xor i32 %A, -1
-  %shl = shl i32 1, %B
-  %and = and i32 %shl, %neg
-  %cmp = icmp ne i32 %and, 0
-; CHECK: @test67
-; CHECK-NEXT: %shl = shl i32 1, %B
-; CHECK-NEXT: %1 = and i32 %shl, %A
-; CHECK-NEXT: %cmp = icmp eq i32 %1, 0
-; CHECK-NEXT: ret i1 %cmp
-  ret i1 %cmp
-}
-
-define i1 @test68(i32 %A, i32 %B) {
-  %neg = xor i32 %A, -1
-  %shl = shl i32 1, %B
-  %and = and i32 %shl, %neg
-  %cmp = icmp eq i32 %and, 0
-; CHECK: @test68
-; CHECK-NEXT: %shl = shl i32 1, %B
-; CHECK-NEXT: %1 = and i32 %shl, %A
-; CHECK-NEXT: %cmp = icmp ne i32 %1, 0
-; CHECK-NEXT: ret i1 %cmp
-  ret i1 %cmp
-}
-- 
2.7.4