[PATCH] D86452: [LV] Fix scalar cost for tail predicated loops
Dave Green via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Sat Dec 12 06:22:06 PST 2020
This revision was automatically updated to reflect the committed changes.
Closed by commit rGab97c9bdb747: [LV] Fix scalar cost for tail predicated loops (authored by dmgreen).
Changed prior to commit:
https://reviews.llvm.org/D86452?vs=287391&id=311390#toc
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D86452/new/
https://reviews.llvm.org/D86452
Files:
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
llvm/test/Transforms/LoopVectorize/ARM/scalar-block-cost.ll
Index: llvm/test/Transforms/LoopVectorize/ARM/scalar-block-cost.ll
===================================================================
--- llvm/test/Transforms/LoopVectorize/ARM/scalar-block-cost.ll
+++ llvm/test/Transforms/LoopVectorize/ARM/scalar-block-cost.ll
@@ -15,7 +15,7 @@
; CHECK-COST-NEXT: LV: Found an estimated cost of 1 for VF 1 For instruction: store i32 %add1, i32* %arrayidx2, align 4
; CHECK-COST-NEXT: LV: Found an estimated cost of 1 for VF 1 For instruction: %exitcond.not = icmp eq i32 %add, %n
; CHECK-COST-NEXT: LV: Found an estimated cost of 0 for VF 1 For instruction: br i1 %exitcond.not, label %exit.loopexit, label %for.body
-; CHECK-COST-NEXT: LV: Scalar loop costs: 2.
+; CHECK-COST-NEXT: LV: Scalar loop costs: 5.
entry:
%cmp8 = icmp sgt i32 %n, 0
Index: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -6483,9 +6483,10 @@
// if-converted. This means that the block's instructions (aside from
// stores and instructions that may divide by zero) will now be
// unconditionally executed. For the scalar case, we may not always execute
- // the predicated block. Thus, scale the block's cost by the probability of
- // executing it.
- if (VF.isScalar() && blockNeedsPredication(BB))
+ // the predicated block, if it is an if-else block. Thus, scale the block's
+ // cost by the probability of executing it. blockNeedsPredication from
+ // Legal is used so as to not include all blocks in tail folded loops.
+ if (VF.isScalar() && Legal->blockNeedsPredication(BB))
BlockCost.first /= getReciprocalPredBlockProb();
Cost.first += BlockCost.first;
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