From: Sanjay Patel <spatel@rotateright.com>
Date: Mon, 15 May 2017 19:27:53 +0000 (+0000)
Subject: [InstCombine] restrict icmp fold with 2 sdiv exact operands (PR32949)
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=6d2022f1d3e2bd776e9f7098ccb63f4fd0bd87ec;p=llvm

[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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@303105 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index e3639db544a..60ed4057ced 100644
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -3068,16 +3068,23 @@ Instruction *InstCombiner::foldICmpBinOp(ICmpInst &I) {
         }
       }
       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();
diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll
index b29931c69d3..6f657b19045 100644
--- a/test/Transforms/InstCombine/icmp.ll
+++ b/test/Transforms/InstCombine/icmp.ll
@@ -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