[llvm] r303105 - [InstCombine] restrict icmp fold with 2 sdiv exact operands (PR32949)

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Mon May 15 14:27:53 2017
New Revision: 303105

URL: http://llvm.org/viewvc/llvm-project?rev=303105&view=rev
Log:
[InstCombine] restrict icmp fold with 2 sdiv exact operands (PR32949)

This is the InstCombine counterpart to D32954. 
I added some comments about the code duplication in:
rL302436

Alive-based verification:
http://rise4fun.com/Alive/dPw

This is a 2nd fix for the problem reported in:
https://bugs.llvm.org/show_bug.cgi?id=32949

Differential Revision: https://reviews.llvm.org/D32970

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
    llvm/trunk/test/Transforms/InstCombine/icmp.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp?rev=303105&r1=303104&r2=303105&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCompares.cpp Mon May 15 14:27:53 2017
@@ -3068,16 +3068,23 @@ Instruction *InstCombiner::foldICmpBinOp
         }
       }
       break;
+
     case Instruction::UDiv:
     case Instruction::LShr:
-      if (I.isSigned())
+      if (I.isSigned() || !BO0->isExact() || !BO1->isExact())
         break;
-      LLVM_FALLTHROUGH;
+      return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
+
     case Instruction::SDiv:
+      if (!I.isEquality() || !BO0->isExact() || !BO1->isExact())
+        break;
+      return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
+
     case Instruction::AShr:
       if (!BO0->isExact() || !BO1->isExact())
         break;
       return new ICmpInst(Pred, BO0->getOperand(0), BO1->getOperand(0));
+
     case Instruction::Shl: {
       bool NUW = BO0->hasNoUnsignedWrap() && BO1->hasNoUnsignedWrap();
       bool NSW = BO0->hasNoSignedWrap() && BO1->hasNoSignedWrap();

Modified: llvm/trunk/test/Transforms/InstCombine/icmp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp.ll?rev=303105&r1=303104&r2=303105&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp.ll Mon May 15 14:27:53 2017
@@ -695,11 +695,13 @@ define i1 @test48(i32 %X, i32 %Y, i32 %Z
   ret i1 %C
 }
 
-; FIXME: The above transform only works for equality predicates.
+; The above transform only works for equality predicates.
 
 define i1 @PR32949(i32 %X, i32 %Y, i32 %Z) {
 ; CHECK-LABEL: @PR32949(
-; CHECK-NEXT:    [[C:%.*]] = icmp sgt i32 %X, %Y
+; CHECK-NEXT:    [[A:%.*]] = sdiv exact i32 %X, %Z
+; CHECK-NEXT:    [[B:%.*]] = sdiv exact i32 %Y, %Z
+; CHECK-NEXT:    [[C:%.*]] = icmp sgt i32 [[A]], [[B]]
 ; CHECK-NEXT:    ret i1 [[C]]
 ;
   %A = sdiv exact i32 %X, %Z