[LV] Check if plan has an early exit via plan's exit blocks. (NFC) #134720
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Add a dedicated function to check if a plan is for a loop with an early exit. This can easily be determined by checking the exit blocks. This allows removing a use of Legal->hasUncountableEarlyExit() from InnerLoopVectorizer.
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@llvm/pr-subscribers-vectorizers @llvm/pr-subscribers-llvm-transforms Author: Florian Hahn (fhahn) ChangesAdd a dedicated function to check if a plan is for a loop with an early exit. This can easily be determined by checking the exit blocks. This allows removing a use of Legal->hasUncountableEarlyExit() from InnerLoopVectorizer. Full diff: https://github.com/llvm/llvm-project/pull/134720.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 5df1061691a67..02dc407e6d56b 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7564,14 +7564,10 @@ VectorizationFactor LoopVectorizationPlanner::computeBestVF() {
VPCostContext CostCtx(CM.TTI, *CM.TLI, Legal->getWidestInductionType(), CM,
CM.CostKind);
precomputeCosts(BestPlan, BestFactor.Width, CostCtx);
- // Set PlanForEarlyExitLoop to true if the BestPlan has been built from a
- // loop with an uncountable early exit. The legacy cost model doesn't
- // properly model costs for such loops.
- bool PlanForEarlyExitLoop =
- BestPlan.getVectorLoopRegion() &&
- BestPlan.getVectorLoopRegion()->getSingleSuccessor() !=
- BestPlan.getMiddleBlock();
- assert((BestFactor.Width == LegacyVF.Width || PlanForEarlyExitLoop ||
+ // Verify that the VPlan-based and legacy cost models agree, except for VPlans
+ // with early exits and plans with additional VPlan simplifications. The
+ // legacy cost model doesn't properly model costs for such loops.
+ assert((BestFactor.Width == LegacyVF.Width || BestPlan.hasEarlyExit() ||
planContainsAdditionalSimplifications(getPlanFor(BestFactor.Width),
CostCtx, OrigLoop) ||
planContainsAdditionalSimplifications(getPlanFor(LegacyVF.Width),
@@ -7782,7 +7778,7 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
// 2.5 When vectorizing the epilogue, fix reduction resume values from the
// additional bypass block.
if (VectorizingEpilogue) {
- assert(!ILV.Legal->hasUncountableEarlyExit() &&
+ assert(!BestVPlan.hasEarlyExit() &&
"Epilogue vectorisation not yet supported with early exits");
BasicBlock *PH = OrigLoop->getLoopPreheader();
BasicBlock *BypassBlock = ILV.getAdditionalBypassBlock();
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index a98d0ecb9a33b..da7aef73f9df3 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -3768,6 +3768,14 @@ class VPlan {
/// successors of the block in VPlan. The returned block is owned by the VPlan
/// and deleted once the VPlan is destroyed.
VPIRBasicBlock *createVPIRBasicBlock(BasicBlock *IRBB);
+
+ /// Returns true if the VPlan is based on a loop with an early exit. That is
+ /// the case if the VPlan has either more than one exit block or a single exit
+ /// block with multiple predecessors (one for the exit via the latch and one
+ /// via the other early exit).
+ bool hasEarlyExit() const {
+ return ExitBlocks.size() > 1 || ExitBlocks[0]->getNumPredecessors() > 1;
+ }
};
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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…s. (NFC) (#134720) Add a dedicated function to check if a plan is for a loop with an early exit. This can easily be determined by checking the exit blocks. This allows removing a use of Legal->hasUncountableEarlyExit() from InnerLoopVectorizer. PR: llvm/llvm-project#134720
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/195/builds/7306 Here is the relevant piece of the build log for the reference |
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Add a dedicated function to check if a plan is for a loop with an early exit. This can easily be determined by checking the exit blocks.
This allows removing a use of Legal->hasUncountableEarlyExit() from InnerLoopVectorizer.