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Revert "Revert r270478 "[LoopUnroll] Enable advanced unrolling analysis by default."" 

This reverts commit r270512 and reapplies r270478. Originally it caused
PR27847, but it was fixed in r270517.

llvm-svn: 270518
This commit is contained in:
Michael Zolotukhin 2016-05-24 01:22:20 +00:00
parent 3898b2b587
commit 96c150d154
2 changed files with 4 additions and 4 deletions
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6
llvm/lib/Transforms/Scalar/LoopUnrollPass.cpp
View File

@ -45,18 +45,18 @@ static cl::opt<unsigned>
cl::desc("The baseline cost threshold for loop unrolling"));
static cl::opt<unsigned> UnrollPercentDynamicCostSavedThreshold(
"unroll-percent-dynamic-cost-saved-threshold", cl::Hidden,
"unroll-percent-dynamic-cost-saved-threshold", cl::init(50), cl::Hidden,
cl::desc("The percentage of estimated dynamic cost which must be saved by "
"unrolling to allow unrolling up to the max threshold."));
static cl::opt<unsigned> UnrollDynamicCostSavingsDiscount(
"unroll-dynamic-cost-savings-discount", cl::Hidden,
"unroll-dynamic-cost-savings-discount", cl::init(100), cl::Hidden,
cl::desc("This is the amount discounted from the total unroll cost when "
"the unrolled form has a high dynamic cost savings (triggered by "
"the '-unroll-perecent-dynamic-cost-saved-threshold' flag)."));
static cl::opt<unsigned> UnrollMaxIterationsCountToAnalyze(
"unroll-max-iteration-count-to-analyze", cl::init(0), cl::Hidden,
"unroll-max-iteration-count-to-analyze", cl::init(10), cl::Hidden,
cl::desc("Don't allow loop unrolling to simulate more than this number of"
"iterations when checking full unroll profitability"));

2
llvm/test/Transforms/LoopUnroll/partial-unroll-const-bounds.ll
View File

@ -1,4 +1,4 @@
; RUN: opt < %s -S -unroll-threshold=20 -loop-unroll -unroll-allow-partial -unroll-runtime | FileCheck %s
; RUN: opt < %s -S -unroll-threshold=20 -loop-unroll -unroll-allow-partial -unroll-runtime -unroll-dynamic-cost-savings-discount=0 | FileCheck %s
; The Loop TripCount is 9. However unroll factors 3 or 9 exceed given threshold.
; The test checks that we choose a smaller, power-of-two, unroll count and do not give up on unrolling.