[llvm] [VPlan] Replace BranchOnCount with Compare + BranchOnCond (NFC). (PR #172181)

[Luke Lau via llvm-commits]

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@@ -3201,27 +3201,25 @@ void VPlanTransforms::canonicalizeEVLLoops(VPlan &Plan) {
   CanonicalIV->eraseFromParent();
 
   // Replace the use of VectorTripCount in the latch-exiting block.
-  // Before: (branch-on-count EVLIVInc, VectorTripCount)
-  // After: (branch-on-cond eq AVLNext, 0)
-
+  // Before: (branch-on-cond (icmp eq EVLIVInc, VectorTripCount))
+  // After: (branch-on-cond icmp eq AVLNext, 0)
   VPBasicBlock *LatchExiting =
       HeaderVPBB->getPredecessors()[1]->getEntryBasicBlock();
   auto *LatchExitingBr = cast<VPInstruction>(LatchExiting->getTerminator());
-  // Skip single-iteration loop region
   if (match(LatchExitingBr, m_BranchOnCond(m_True())))
     return;
-  assert(LatchExitingBr &&
-         match(LatchExitingBr,
-               m_BranchOnCount(m_VPValue(EVLIncrement),
-                               m_Specific(&Plan.getVectorTripCount()))) &&
-         "Unexpected terminator in EVL loop");
+
+  assert(match(LatchExitingBr, m_BranchOnCond(m_SpecificCmp(
+                                   CmpInst::ICMP_EQ, m_VPValue(EVLIncrement),
+                                   m_Specific(&Plan.getVectorTripCount())))) &&
+         "Expected BranchOnCond with ICmp comparing EVL increment with vector "
+         "trip count");
 
   Type *AVLTy = VPTypeAnalysis(Plan).inferScalarType(AVLNext);
   VPBuilder Builder(LatchExitingBr);
-  VPValue *Cmp = Builder.createICmp(CmpInst::ICMP_EQ, AVLNext,
-                                    Plan.getConstantInt(AVLTy, 0));
-  Builder.createNaryOp(VPInstruction::BranchOnCond, Cmp);
-  LatchExitingBr->eraseFromParent();
+  LatchExitingBr->setOperand(0,
+                             Builder.createICmp(CmpInst::ICMP_EQ, AVLNext,
+                                                Plan.getConstantInt(AVLTy, 0)));
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lukel97 wrote:

I think this will leave behind a potentially dead icmp but that should be ok since we run removeDeadRecipes afterwards?

https://github.com/llvm/llvm-project/pull/172181