[LFTR] Assert and simplify under assumption exit counts are integers

[reames]

Summary

This invariant was introduced in 8f3d16905d75b07a933d01dc29677fe5867c1b3e. This change should be entirely obvious; I'm posting for review just for a sanity check.

[reames]

Another simplification.

[nikic]

LGTM

llvm/lib/Transforms/Scalar/IndVarSimplify.cpp

 
 /// Insert an IR expression which computes the value held by the IV IndVar
 /// (which must be an loop counter w/unit stride) after the backedge of loop L
 /// is taken ExitCount times.
 static Value *genLoopLimit(PHINode *IndVar, BasicBlock *ExitingBB,
                            const SCEV *ExitCount, bool UsePostInc, Loop *L,
                            SCEVExpander &Rewriter, ScalarEvolution *SE) {
   assert(isLoopCounter(IndVar, L, SE));
+  assert(ExitCount->getType()->isIntegerTy() && "exit count must be integer");
   const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(SE->getSCEV(IndVar));
   const SCEV *IVInit = AR->getStart();
   assert(AR->getStepRecurrence(*SE)->isOne() && "only handles unit stride");
 
   // IVInit may be a pointer while ExitCount is an integer when FindLoopCounter
   // finds a valid pointer IV. Sign extend ExitCount in order to materialize a
   // GEP. Avoid running SCEVExpander on a new pointer value, instead reusing
   // the existing GEPs whenever possible.
-  if (IndVar->getType()->isPointerTy() &&
-      !ExitCount->getType()->isPointerTy()) {
+  if (IndVar->getType()->isPointerTy()) {
     // IVOffset will be the new GEP offset that is interpreted by GEP as a
     // signed value. ExitCount on the other hand represents the loop trip count,
     // which is an unsigned value. FindLoopCounter only allows induction
     // variables that have a positive unit stride of one. This means we don't
     // have to handle the case of negative offsets (yet) and just need to zero
     // extend ExitCount.
     Type *OfsTy = SE->getEffectiveSCEVType(IVInit->getType());
     const SCEV *IVOffset = SE->getTruncateOrZeroExtend(ExitCount, OfsTy);
if (UsePostInc)
       IVLimit = SE->getAddExpr(IVLimit, SE->getOne(IVLimit->getType()));
 
     // Expand the code for the iteration count.
     assert(SE->isLoopInvariant(IVLimit, L) &&
            "Computed iteration count is not loop invariant!");
     // Ensure that we generate the same type as IndVar, or a smaller integer
     // type. In the presence of null pointer values, we have an integer type
     // SCEV expression (IVInit) for a pointer type IV value (IndVar).
-    Type *LimitTy = ExitCount->getType()->isPointerTy() ?
-      IndVar->getType() : ExitCount->getType();
+    Type *LimitTy = ExitCount->getType();
     BranchInst *BI = cast<BranchInst>(ExitingBB->getTerminator());
     return Rewriter.expandCodeFor(IVLimit, LimitTy, BI);
   }
 }
 
 /// This method rewrites the exit condition of the loop to be a canonical !=
 /// comparison against the incremented loop induction variable.  This pass is
 /// able to rewrite the exit tests of any loop where the SCEV analysis can