[llvm] r186229 - Fix logic error optimizing "icmp pred (urem X, Y), Y" where pred is signed.

[Nick Lewycky]

Author: nicholas
Date: Fri Jul 12 18:42:57 2013
New Revision: 186229

URL: http://llvm.org/viewvc/llvm-project?rev=186229&view=rev
Log:
Fix logic error optimizing "icmp pred (urem X, Y), Y" where pred is signed.
Fixes PR16605.

Modified:
    llvm/trunk/lib/Analysis/InstructionSimplify.cpp
    llvm/trunk/test/Transforms/InstSimplify/compare.ll

Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=186229&r1=186228&r2=186229&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Fri Jul 12 18:42:57 2013
@@ -2246,6 +2246,7 @@ static Value *SimplifyICmpInst(unsigned
     }
   }
 
+  // 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
       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
       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
       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
       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
       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

Modified: llvm/trunk/test/Transforms/InstSimplify/compare.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/compare.ll?rev=186229&r1=186228&r2=186229&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/compare.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/compare.ll Fri Jul 12 18:42:57 2013
@@ -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