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LoopVectorizer: Don't count the induction variable multiple times

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When estimating register pressure, don't count the induction variable mulitple
times. It is unlikely to be unrolled. This is currently disabled and hidden
behind a flag ("enable-ind-var-reg-heur").

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200371 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer 2014-01-29 04:36:12 +00:00
parent c86f56a506
commit 8dc253e97b
1 changed files with 9 additions and 0 deletions
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9
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -188,6 +188,10 @@ static cl::opt<unsigned> NumberOfStoresToPredicate(
"vectorize-num-stores-pred", cl::init(0), cl::Hidden,
cl::desc("Max number of stores to be predicated behind an if."));
static cl::opt<bool> EnableIndVarRegisterHeur(
"enable-ind-var-reg-heur", cl::init(false), cl::Hidden,
cl::desc("Count the induction variable only once when unrolling"));
static cl::opt<bool> EnableCondStoresVectorization(
"enable-cond-stores-vec", cl::init(false), cl::Hidden,
cl::desc("Enable if predication of stores during vectorization."));
@ -5155,6 +5159,11 @@ LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
unsigned UF = PowerOf2Floor((TargetNumRegisters - R.LoopInvariantRegs) /
R.MaxLocalUsers);
// Don't count the induction variable as unrolled.
if (EnableIndVarRegisterHeur)
UF = PowerOf2Floor((TargetNumRegisters - R.LoopInvariantRegs - 1) /
std::max(1U, (R.MaxLocalUsers - 1)));
// Clamp the unroll factor ranges to reasonable factors.
unsigned MaxUnrollSize = TTI.getMaximumUnrollFactor();