IndVarSimplify: thread CmpPredicate to SCEV (NFC) (#125240)

Relevant parts of ScalarEvolution's API accept a CmpPredicate instead of
a CmpInst::Predicate after 60dc450 (SCEV: migrate to CmpPredicate
(NFC)). After auditing the callers of these APIs, it was found that
IndVarSimplify was dropping samesign information. Fix this.

Author: artagnon

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

@@ -1262,14 +1262,14 @@ static std::optional<Value *>
 createReplacement(ICmpInst *ICmp, const Loop *L, BasicBlock *ExitingBB,
                   const SCEV *MaxIter, bool Inverted, bool SkipLastIter,
                   ScalarEvolution *SE, SCEVExpander &Rewriter) {
-  ICmpInst::Predicate Pred = ICmp->getPredicate();
+  CmpPredicate Pred = ICmp->getCmpPredicate();
   Value *LHS = ICmp->getOperand(0);
   Value *RHS = ICmp->getOperand(1);
 
   // 'LHS pred RHS' should now mean that we stay in loop.
   auto *BI = cast<BranchInst>(ExitingBB->getTerminator());
   if (Inverted)
-    Pred = CmpInst::getInversePredicate(Pred);
+    Pred = ICmpInst::getInverseCmpPredicate(Pred);
 
   const SCEV *LHSS = SE->getSCEVAtScope(LHS, L);
   const SCEV *RHSS = SE->getSCEVAtScope(RHS, L);

llvm/lib/Transforms/Utils/SimplifyIndVar.cpp

@@ -205,12 +205,12 @@ bool SimplifyIndvar::makeIVComparisonInvariant(ICmpInst *ICmp,
   if (!Preheader)
     return false;
   unsigned IVOperIdx = 0;
-  ICmpInst::Predicate Pred = ICmp->getPredicate();
+  CmpPredicate Pred = ICmp->getCmpPredicate();
   if (IVOperand != ICmp->getOperand(0)) {
     // Swapped
     assert(IVOperand == ICmp->getOperand(1) && "Can't find IVOperand");
     IVOperIdx = 1;
-    Pred = ICmpInst::getSwappedPredicate(Pred);
+    Pred = ICmpInst::getSwappedCmpPredicate(Pred);
   }
 
   // Get the SCEVs for the ICmp operands (in the specific context of the
@@ -249,13 +249,13 @@ bool SimplifyIndvar::makeIVComparisonInvariant(ICmpInst *ICmp,
 void SimplifyIndvar::eliminateIVComparison(ICmpInst *ICmp,
                                            Instruction *IVOperand) {
   unsigned IVOperIdx = 0;
-  ICmpInst::Predicate Pred = ICmp->getPredicate();
+  CmpPredicate Pred = ICmp->getCmpPredicate();
   ICmpInst::Predicate OriginalPred = Pred;
   if (IVOperand != ICmp->getOperand(0)) {
     // Swapped
     assert(IVOperand == ICmp->getOperand(1) && "Can't find IVOperand");
     IVOperIdx = 1;
-    Pred = ICmpInst::getSwappedPredicate(Pred);
+    Pred = ICmpInst::getSwappedCmpPredicate(Pred);
   }
 
   // Get the SCEVs for the ICmp operands (in the specific context of the