[IndVars] Split NumElimCmp statistic into three pieces (#170514)

Only one of the three update paths actual eliminates the comparison.

While here, use early return to clarify the code structure.

Author: preames

llvm/lib/Transforms/Utils/SimplifyIndVar.cpp

@@ -43,7 +43,9 @@ STATISTIC(
 STATISTIC(
     NumSimplifiedSRem,
     "Number of IV signed remainder operations converted to unsigned remainder");
-STATISTIC(NumElimCmp     , "Number of IV comparisons eliminated");
+STATISTIC(NumElimCmp, "Number of IV comparisons eliminated");
+STATISTIC(NumInvariantCmp, "Number of IV comparisons made loop invariant");
+STATISTIC(NumSameSign, "Number of IV comparisons with new samesign flags");
 
 namespace {
   /// This is a utility for simplifying induction variables
@@ -275,11 +277,20 @@ void SimplifyIndvar::eliminateIVComparison(ICmpInst *ICmp,
     ICmp->replaceAllUsesWith(ConstantInt::getBool(ICmp->getContext(), *Ev));
     DeadInsts.emplace_back(ICmp);
     LLVM_DEBUG(dbgs() << "INDVARS: Eliminated comparison: " << *ICmp << '\n');
-  } else if (makeIVComparisonInvariant(ICmp, IVOperand)) {
-    // fallthrough to end of function
-  } else if ((ICmpInst::isSigned(OriginalPred) ||
-              (ICmpInst::isUnsigned(OriginalPred) && !ICmp->hasSameSign())) &&
-             SE->haveSameSign(S, X)) {
+    ++NumElimCmp;
+    Changed = true;
+    return;
+  }
+
+  if (makeIVComparisonInvariant(ICmp, IVOperand)) {
+    ++NumInvariantCmp;
+    Changed = true;
+    return;
+  }
+
+  if ((ICmpInst::isSigned(OriginalPred) ||
+       (ICmpInst::isUnsigned(OriginalPred) && !ICmp->hasSameSign())) &&
+      SE->haveSameSign(S, X)) {
     // Set the samesign flag on the compare if legal, and canonicalize to
     // the unsigned variant (for signed compares) hoping that it will open
     // the doors for other optimizations.  Note that we cannot rely on Pred
@@ -289,11 +300,10 @@ void SimplifyIndvar::eliminateIVComparison(ICmpInst *ICmp,
                       << '\n');
     ICmp->setPredicate(ICmpInst::getUnsignedPredicate(OriginalPred));
     ICmp->setSameSign();
-  } else
+    NumSameSign++;
+    Changed = true;
     return;
-
-  ++NumElimCmp;
-  Changed = true;
+  }
 }
 
 bool SimplifyIndvar::eliminateSDiv(BinaryOperator *SDiv) {