[PATCH] D146468: [LFTR] Use evaluateAtIteration in genLoopLimit [nfc]
Philip Reames via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Tue Mar 21 19:18:34 PDT 2023
This revision was automatically updated to reflect the committed changes.
Closed by commit rG206dc5453477: [LFTR] Use evaluateAtIteration in genLoopLimit [nfc] (authored by reames).
Changed prior to commit:
https://reviews.llvm.org/D146468?vs=506764&id=507207#toc
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D146468/new/
https://reviews.llvm.org/D146468
Files:
llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
Index: llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -914,28 +914,14 @@
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.
+ // finds a valid pointer IV.
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)
- IVOffset = SE->getAddExpr(IVOffset, SE->getOne(OfsTy));
-
- // Expand the code for the iteration count.
- assert(SE->isLoopInvariant(IVOffset, L) &&
+ const SCEVAddRecExpr *ARBase = UsePostInc ? AR->getPostIncExpr(*SE) : AR;
+ const SCEV *IVLimit = ARBase->evaluateAtIteration(ExitCount, *SE);
+ assert(SE->isLoopInvariant(IVLimit, L) &&
"Computed iteration count is not loop invariant!");
-
- const SCEV *IVLimit = SE->getAddExpr(IVInit, IVOffset);
- BranchInst *BI = cast<BranchInst>(ExitingBB->getTerminator());
- return Rewriter.expandCodeFor(IVLimit, IndVar->getType(), BI);
+ return Rewriter.expandCodeFor(IVLimit, IndVar->getType(),
+ ExitingBB->getTerminator());
} else {
// In any other case, convert both IVInit and ExitCount to integers before
// comparing. This may result in SCEV expansion of pointers, but in practice
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