From 8a23270ce60fdd5dafa1c8dfbf9f46c8efe244b7 Mon Sep 17 00:00:00 2001
From: Nick Lewycky <nicholas@mxc.ca>
Date: Fri, 12 Jul 2013 23:42:57 +0000
Subject: [PATCH] Fix logic error optimizing "icmp pred (urem X, Y), Y" where
 pred is signed. Fixes PR16605.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186229 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/InstructionSimplify.cpp    | 11 +++++++----
 test/Transforms/InstSimplify/compare.ll | 10 +++++++++-
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index d66ecca928a..52c04565862 100644
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -2246,6 +2246,7 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
     }
   }
 
+  // icmp pred (urem X, Y), Y
   if (LBO && match(LBO, m_URem(m_Value(), m_Specific(RHS)))) {
     bool KnownNonNegative, KnownNegative;
     switch (Pred) {
@@ -2253,7 +2254,7 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
       break;
     case ICmpInst::ICMP_SGT:
     case ICmpInst::ICMP_SGE:
-      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD);
+      ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD);
       if (!KnownNonNegative)
         break;
       // fall-through
@@ -2263,7 +2264,7 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
       return getFalse(ITy);
     case ICmpInst::ICMP_SLT:
     case ICmpInst::ICMP_SLE:
-      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD);
+      ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD);
       if (!KnownNonNegative)
         break;
       // fall-through
@@ -2273,6 +2274,8 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
       return getTrue(ITy);
     }
   }
+
+  // icmp pred X, (urem Y, X)
   if (RBO && match(RBO, m_URem(m_Value(), m_Specific(LHS)))) {
     bool KnownNonNegative, KnownNegative;
     switch (Pred) {
@@ -2280,7 +2283,7 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
       break;
     case ICmpInst::ICMP_SGT:
     case ICmpInst::ICMP_SGE:
-      ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD);
+      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD);
       if (!KnownNonNegative)
         break;
       // fall-through
@@ -2290,7 +2293,7 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS,
       return getTrue(ITy);
     case ICmpInst::ICMP_SLT:
     case ICmpInst::ICMP_SLE:
-      ComputeSignBit(RHS, KnownNonNegative, KnownNegative, Q.TD);
+      ComputeSignBit(LHS, KnownNonNegative, KnownNegative, Q.TD);
       if (!KnownNonNegative)
         break;
       // fall-through
diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll
index 82d56028c37..a0a9c8540ab 100644
--- a/test/Transforms/InstSimplify/compare.ll
+++ b/test/Transforms/InstSimplify/compare.ll
@@ -480,7 +480,7 @@ define i1 @urem5(i16 %X, i32 %Y) {
   %B = urem i32 %A, %Y
   %C = icmp slt i32 %B, %Y
   ret i1 %C
-; CHECK: ret i1 true
+; CHECK-NOT: ret i1 true
 }
 
 define i1 @urem6(i32 %X, i32 %Y) {
@@ -491,6 +491,14 @@ define i1 @urem6(i32 %X, i32 %Y) {
 ; CHECK: ret i1 true
 }
 
+define i1 @urem7(i32 %X) {
+; CHECK: @urem7
+  %A = urem i32 1, %X
+  %B = icmp sgt i32 %A, %X
+  ret i1 %B
+; CHECK-NOT: ret i1 false
+}
+
 define i1 @srem1(i32 %X) {
 ; CHECK: @srem1
   %A = srem i32 %X, -5
-- 
2.34.1