From 63522b1998289e694385a45a719313c95f3350cf Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Wed, 12 Dec 2012 20:48:54 +0000
Subject: [PATCH] Simplify negated bit test

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170020 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstCombineCompares.cpp       | 18 +++++++++++++
 test/Transforms/InstCombine/icmp.ll           | 26 +++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 1b96c3cca4e..b0fc82f6f66 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2034,6 +2034,15 @@ 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()) && isPowerOfTwo(X, TD)) {
+        return new ICmpInst(ICmpInst::ICMP_NE,
+                            Builder->CreateAnd(X, Y),
+                            Op1);
+      }
+
       break;
     }
     case ICmpInst::ICMP_NE: {
@@ -2071,6 +2080,15 @@ 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()) && isPowerOfTwo(X, TD)) {
+        return new ICmpInst(ICmpInst::ICMP_EQ,
+                            Builder->CreateAnd(X, Y),
+                            Op1);
+      }
+
       break;
     }
     case ICmpInst::ICMP_ULT:
diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll
index 8e064a4f2fc..d11b6cc756f 100644
--- a/test/Transforms/InstCombine/icmp.ll
+++ b/test/Transforms/InstCombine/icmp.ll
@@ -677,3 +677,29 @@ 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
+}