[llvm] [InstCombine] Avoid rewriting multi-use post-inc latch icmps (preserve nsw/nuw for later passes) (PR #215960)

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``````````bash
git-clang-format --diff origin/main HEAD --extensions cpp,h -- llvm/include/llvm/Analysis/ScalarEvolution.h llvm/lib/Analysis/ScalarEvolution.cpp llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp --diff_from_common_commit
``````````

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in a stack if you are using a stacked PR workflow. You can limit the results by
changing `origin/main` to the base branch/commit you want to compare against.
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``````````diff
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 93564d989..40ce90643 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -9593,9 +9593,8 @@ ScalarEvolution::ExitLimit ScalarEvolution::computeExitLimitFromICmp(
       return EL;
 
     // X < (Y+1) failed to get an exact count. Try the pre-inc form.
-    ExitLimit PreEL = howManyLessThansViaPreInc(OrigLHS, OrigRHS, L, IsSigned,
-                                                ControlsOnlyExit,
-                                                AllowPredicates);
+    ExitLimit PreEL = howManyLessThansViaPreInc(
+        OrigLHS, OrigRHS, L, IsSigned, ControlsOnlyExit, AllowPredicates);
     if (PreEL.hasFullInfo())
       return PreEL;
 
@@ -9618,10 +9617,9 @@ ScalarEvolution::ExitLimit ScalarEvolution::computeExitLimitFromICmp(
     // SimplifyICmpOperands may have rewritten an original X <= Y into
     // X < (Y + 1). Retry with the pre-inc form of the original compare.
     if (OrigPred == ICmpInst::ICMP_ULE || OrigPred == ICmpInst::ICMP_SLE) {
-      ExitLimit PreEL = howManyLessThansViaPreInc(OrigLHS, OrigRHS, L,
-                                                  ICmpInst::isSigned(OrigPred),
-                                                  ControlsOnlyExit,
-                                                  AllowPredicates);
+      ExitLimit PreEL = howManyLessThansViaPreInc(
+          OrigLHS, OrigRHS, L, ICmpInst::isSigned(OrigPred), ControlsOnlyExit,
+          AllowPredicates);
       if (PreEL.hasFullInfo())
         return PreEL;
       if (!EL.hasAnyInfo() && PreEL.hasAnyInfo())
@@ -13438,8 +13436,7 @@ ScalarEvolution::ExitLimit ScalarEvolution::howManyLessThansViaPreInc(
     return getCouldNotCompute();
 
   const auto *AR = dyn_cast<SCEVAddRecExpr>(LHS);
-  SCEV::NoWrapFlags NoWrapFlag =
-      IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW;
+  SCEV::NoWrapFlags NoWrapFlag = IsSigned ? SCEV::FlagNSW : SCEV::FlagNUW;
   if (!AR || AR->getLoop() != L || !AR->isAffine() ||
       !AR->getNoWrapFlags(NoWrapFlag))
     return getCouldNotCompute();
@@ -13452,8 +13449,7 @@ ScalarEvolution::ExitLimit ScalarEvolution::howManyLessThansViaPreInc(
 
   const SCEV *PreStart = getMinusSCEV(AR->getStart(), Step);
   // Do not transfer nowrap flags from the post-inc AddRec to its sibling.
-  const SCEV *PreAR =
-      getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap);
+  const SCEV *PreAR = getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap);
 
   const APInt &StepV = StepC->getAPInt();
   auto IsMultipleOfStep = [&](const SCEV *S) {

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https://github.com/llvm/llvm-project/pull/215960