From 7d2cbd2d43c389c0d067d30683ffefb6e4edde66 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 9 May 2008 05:19:28 +0000
Subject: [PATCH] Implement PR2298.  This transforms:    ~x < ~y --> y < x   
 -x == -y --> x == y

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50882 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/InstructionCombining.cpp | 13 +++++++++++++
 test/Transforms/InstCombine/not.ll             | 10 ++++++++++
 test/Transforms/InstCombine/sub.ll             | 10 ++++++++++
 3 files changed, 33 insertions(+)

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 772ef63121b..e8b60f890c2 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -5658,8 +5658,21 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
         return R;
   }
   
+  // ~x < ~y --> y < x
+  { Value *A, *B;
+    if (match(Op0, m_Not(m_Value(A))) &&
+        match(Op1, m_Not(m_Value(B))))
+      return new ICmpInst(I.getPredicate(), B, A);
+  }
+  
   if (I.isEquality()) {
     Value *A, *B, *C, *D;
+    
+    // -x == -y --> x == y
+    if (match(Op0, m_Neg(m_Value(A))) &&
+        match(Op1, m_Neg(m_Value(B))))
+      return new ICmpInst(I.getPredicate(), A, B);
+    
     if (match(Op0, m_Xor(m_Value(A), m_Value(B)))) {
       if (A == Op1 || B == Op1) {    // (A^B) == A  ->  B == 0
         Value *OtherVal = A == Op1 ? B : A;
diff --git a/test/Transforms/InstCombine/not.ll b/test/Transforms/InstCombine/not.ll
index 757e1de940c..a79e5187181 100644
--- a/test/Transforms/InstCombine/not.ll
+++ b/test/Transforms/InstCombine/not.ll
@@ -42,3 +42,13 @@ define i32 @test5(i32 %A, i32 %B) {
         ret i32 %d
 }
 
+; PR2298
+define i8 @test6(i32 %a, i32 %b) zeroext nounwind  {
+entry:
+	%tmp1not = xor i32 %a, -1		; <i32> [#uses=1]
+	%tmp2not = xor i32 %b, -1		; <i32> [#uses=1]
+	%tmp3 = icmp slt i32 %tmp1not, %tmp2not		; <i1> [#uses=1]
+	%retval67 = zext i1 %tmp3 to i8		; <i8> [#uses=1]
+	ret i8 %retval67
+}
+
diff --git a/test/Transforms/InstCombine/sub.ll b/test/Transforms/InstCombine/sub.ll
index 9ee8b068450..da6d710f6bc 100644
--- a/test/Transforms/InstCombine/sub.ll
+++ b/test/Transforms/InstCombine/sub.ll
@@ -134,3 +134,13 @@ define i1 @test21(i32 %g, i32 %h) {
 	%tmp.4 = icmp ne i32 %tmp.2, %g		; <i1> [#uses=1]
 	ret i1 %tmp.4
 }
+
+; PR2298
+define i8 @test22(i32 %a, i32 %b) zeroext nounwind  {
+	%tmp2 = sub i32 0, %a		; <i32> [#uses=1]
+	%tmp4 = sub i32 0, %b		; <i32> [#uses=1]
+	%tmp5 = icmp eq i32 %tmp2, %tmp4		; <i1> [#uses=1]
+	%retval89 = zext i1 %tmp5 to i8		; <i8> [#uses=1]
+	ret i8 %retval89
+}
+