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[LV] Add option --bypass-vf-comparison to bypass VF comparison. NFC #110460

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[LV] Add option --bypass-vf-comparison to bypass VF comparison. NFC #110460

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14 changes: 12 additions & 2 deletions llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -384,6 +384,13 @@ static cl::opt<bool> UseWiderVFIfCallVariantsPresent(
cl::Hidden,
cl::desc("Try wider VFs if they enable the use of vector variants"));

// Bypass the assertion when the VF selected by vplan-based cost model is
// different from the VF selected by legacy cost model.
static cl::opt<bool>
BypassVFComparison("bypass-vf-comparison", cl::init(false), cl::Hidden,
cl::desc("Bypass VF comparison between legacy cost "
"model and the vplan-base cost model."));

// Likelyhood of bypassing the vectorized loop because assumptions about SCEV
// variables not overflowing do not hold. See `emitSCEVChecks`.
static constexpr uint32_t SCEVCheckBypassWeights[] = {1, 127};
Expand Down Expand Up @@ -7383,10 +7390,13 @@ VectorizationFactor LoopVectorizationPlanner::computeBestVF() {
// different VF to be picked by the VPlan-based cost model.
VPCostContext CostCtx(CM.TTI, *CM.TLI, Legal->getWidestInductionType(), CM);
precomputeCosts(BestPlan, BestFactor.Width, CostCtx);
assert((BestFactor.Width == LegacyVF.Width ||
assert(BypassVFComparison ||
(BestFactor.Width == LegacyVF.Width ||
planContainsAdditionalSimplifications(getPlanFor(BestFactor.Width),
CostCtx, OrigLoop)) &&
" VPlan cost model and legacy cost model disagreed");
" VPlan cost model and legacy cost model disagreed. Please report "
"the issue and you can bypass "
"this assertion by `-bypass-vf-comparison=true`.");
assert((BestFactor.Width.isScalar() || BestFactor.ScalarCost > 0) &&
"when vectorizing, the scalar cost must be computed.");
#endif
Expand Down