From 6af608b8cecaf85ec0c0c670fbe79023e0a0bf45 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 11 Jul 2008 04:20:58 +0000
Subject: [PATCH] Fix folding of icmp's of i1 where the comparison is signed. 
 The code was using the algorithm for folding unsigned comparisons which is
 completely wrong.  This has been broken since the signless types change.

llvm-svn: 53444
---
 .../Scalar/InstructionCombining.cpp           | 32 +++++++++++++------
 .../InstCombine/2008-07-10-CastSextBool.ll    | 11 ++++++-
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index 8cc7c05425b9..409d29c2a49c 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -5196,34 +5196,46 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
   if (Ty == Type::Int1Ty) {
     switch (I.getPredicate()) {
     default: assert(0 && "Invalid icmp instruction!");
-    case ICmpInst::ICMP_EQ: {               // icmp eq bool %A, %B -> ~(A^B)
+    case ICmpInst::ICMP_EQ: {               // icmp eq i1 A, B -> ~(A^B)
       Instruction *Xor = BinaryOperator::CreateXor(Op0, Op1, I.getName()+"tmp");
       InsertNewInstBefore(Xor, I);
       return BinaryOperator::CreateNot(Xor);
     }
-    case ICmpInst::ICMP_NE:                  // icmp eq bool %A, %B -> A^B
+    case ICmpInst::ICMP_NE:                  // icmp eq i1 A, B -> A^B
       return BinaryOperator::CreateXor(Op0, Op1);
 
     case ICmpInst::ICMP_UGT:
-    case ICmpInst::ICMP_SGT:
-      std::swap(Op0, Op1);                   // Change icmp gt -> icmp lt
+      std::swap(Op0, Op1);                   // Change icmp ugt -> icmp ult
       // FALL THROUGH
-    case ICmpInst::ICMP_ULT:
-    case ICmpInst::ICMP_SLT: {               // icmp lt bool A, B -> ~X & Y
+    case ICmpInst::ICMP_ULT:{               // icmp ult i1 A, B -> ~A & B
       Instruction *Not = BinaryOperator::CreateNot(Op0, I.getName()+"tmp");
       InsertNewInstBefore(Not, I);
       return BinaryOperator::CreateAnd(Not, Op1);
     }
+    case ICmpInst::ICMP_SGT:
+      std::swap(Op0, Op1);                   // Change icmp sgt -> icmp slt
+      // FALL THROUGH
+    case ICmpInst::ICMP_SLT: {               // icmp slt i1 A, B -> A & ~B
+      Instruction *Not = BinaryOperator::CreateNot(Op1, I.getName()+"tmp");
+      InsertNewInstBefore(Not, I);
+      return BinaryOperator::CreateAnd(Not, Op0);
+    }
     case ICmpInst::ICMP_UGE:
-    case ICmpInst::ICMP_SGE:
-      std::swap(Op0, Op1);                   // Change icmp ge -> icmp le
+      std::swap(Op0, Op1);                   // Change icmp uge -> icmp ule
       // FALL THROUGH
-    case ICmpInst::ICMP_ULE:
-    case ICmpInst::ICMP_SLE: {               //  icmp le bool %A, %B -> ~A | B
+    case ICmpInst::ICMP_ULE: {               //  icmp ule i1 A, B -> ~A | B
       Instruction *Not = BinaryOperator::CreateNot(Op0, I.getName()+"tmp");
       InsertNewInstBefore(Not, I);
       return BinaryOperator::CreateOr(Not, Op1);
     }
+    case ICmpInst::ICMP_SGE:
+      std::swap(Op0, Op1);                   // Change icmp sge -> icmp sle
+      // FALL THROUGH
+    case ICmpInst::ICMP_SLE: {               //  icmp sle i1 A, B -> A | ~B
+      Instruction *Not = BinaryOperator::CreateNot(Op1, I.getName()+"tmp");
+      InsertNewInstBefore(Not, I);
+      return BinaryOperator::CreateOr(Not, Op0);
+    }
     }
   }
 
diff --git a/llvm/test/Transforms/InstCombine/2008-07-10-CastSextBool.ll b/llvm/test/Transforms/InstCombine/2008-07-10-CastSextBool.ll
index f5efefb0a0be..205e57d79738 100644
--- a/llvm/test/Transforms/InstCombine/2008-07-10-CastSextBool.ll
+++ b/llvm/test/Transforms/InstCombine/2008-07-10-CastSextBool.ll
@@ -1,8 +1,17 @@
 ; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {%C = xor i1 %A, true}
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {ret i1 false}
 ; PR2539
 
-define i1 @test(i1 %A) {
+define i1 @test1(i1 %A) {
 	%B = zext i1 %A to i32
 	%C = icmp slt i32 %B, 1
 	ret i1 %C
 }
+
+
+define i1 @test2(i1 zeroext  %b) {
+entry:
+	%cmptmp = icmp slt i1 %b, true		; <i1> [#uses=1]
+	ret i1 %cmptmp
+}
+
-- 
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