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[vectorizer] Add some flags which are useful for conducting experiments

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with the unrolling behavior in the loop vectorizer. No functionality
changed at this point.

These are a bit hack-y, but talking with Hal, there doesn't seem to be
a cleaner way to easily experiment with different thresholds here and he
was also interested in them so I wanted to commit them. Suggestions for
improvement are very welcome here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200212 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2014-01-27 11:12:19 +00:00
parent 3fa842d791
commit 9f22a8788f
1 changed files with 38 additions and 2 deletions
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40
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -139,11 +139,30 @@ static const unsigned RuntimeMemoryCheckThreshold = 8;
/// Maximum simd width.
static const unsigned MaxVectorWidth = 64;
static cl::opt<unsigned> ForceTargetNumScalarRegs(
"force-target-num-scalar-regs", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's number of scalar registers."));
static cl::opt<unsigned> ForceTargetNumVectorRegs(
"force-target-num-vector-regs", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's number of vector registers."));
/// Maximum vectorization unroll count.
static const unsigned MaxUnrollFactor = 16;
/// The cost of a loop that is considered 'small' by the unroller.
static const unsigned SmallLoopCost = 20;
static cl::opt<unsigned> ForceTargetMaxScalarUnrollFactor(
"force-target-max-scalar-unroll", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's max unroll factor for scalar "
"loops."));
static cl::opt<unsigned> ForceTargetMaxVectorUnrollFactor(
"force-target-max-vector-unroll", cl::init(0), cl::Hidden,
cl::desc("A flag that overrides the target's max unroll factor for "
"vectorized loops."));
static cl::opt<unsigned> SmallLoopCost(
"small-loop-cost", cl::init(20), cl::Hidden,
cl::desc("The cost of a loop that is considered 'small' by the unroller."));
namespace {
@ -4966,6 +4985,14 @@ LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
DEBUG(dbgs() << "LV: The target has " << TargetNumRegisters <<
" registers\n");
if (VF == 1) {
if (ForceTargetNumScalarRegs.getNumOccurrences() > 0)
TargetNumRegisters = ForceTargetNumScalarRegs;
} else {
if (ForceTargetNumVectorRegs.getNumOccurrences() > 0)
TargetNumRegisters = ForceTargetNumVectorRegs;
}
LoopVectorizationCostModel::RegisterUsage R = calculateRegisterUsage();
// We divide by these constants so assume that we have at least one
// instruction that uses at least one register.
@ -4983,6 +5010,15 @@ LoopVectorizationCostModel::selectUnrollFactor(bool OptForSize,
// Clamp the unroll factor ranges to reasonable factors.
unsigned MaxUnrollSize = TTI.getMaximumUnrollFactor();
// Check if the user has overridden the unroll max.
if (VF == 1) {
if (ForceTargetMaxScalarUnrollFactor.getNumOccurrences() > 0)
MaxUnrollSize = ForceTargetMaxScalarUnrollFactor;
} else {
if (ForceTargetMaxVectorUnrollFactor.getNumOccurrences() > 0)
MaxUnrollSize = ForceTargetMaxVectorUnrollFactor;
}
// If we did not calculate the cost for VF (because the user selected the VF)
// then we calculate the cost of VF here.
if (LoopCost == 0)