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LoopVectorizer: Calculate the number of pointers to disambiguate at runtime based on the numbers of reads and writes.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180593 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nadav Rotem
2013-04-26 05:08:59 +00:00
parent 276b8549ee
commit 7557e521e5
2 changed files with 95 additions and 4 deletions
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15
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -114,9 +114,9 @@ TinyTripCountVectorThreshold("vectorizer-min-trip-count", cl::init(16),
/// We don't unroll loops with a known constant trip count below this number.
static const unsigned TinyTripCountUnrollThreshold = 128;
/// When performing a runtime memory check, do not check more than this
/// number of pointers. Notice that the check is quadratic!
static const unsigned RuntimeMemoryCheckThreshold = 4;
/// When performing memory disambiguation checks at runtime do not make more
/// than this number of comparisons.
static const unsigned RuntimeMemoryCheckThreshold = 8;
/// We use a metadata with this name to indicate that a scalar loop was
/// vectorized and that we don't need to re-vectorize it if we run into it
@ -2679,6 +2679,9 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
return true;
}
unsigned NumReadPtrs = 0;
unsigned NumWritePtrs = 0;
// Find pointers with computable bounds. We are going to use this information
// to place a runtime bound check.
bool CanDoRT = true;
@ -2687,6 +2690,7 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
Value *V = (*MI).first;
if (hasComputableBounds(V)) {
PtrRtCheck.insert(SE, TheLoop, V, true);
NumWritePtrs++;
DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *V <<"\n");
} else {
CanDoRT = false;
@ -2697,6 +2701,7 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
Value *V = (*MI).first;
if (hasComputableBounds(V)) {
PtrRtCheck.insert(SE, TheLoop, V, false);
NumReadPtrs++;
DEBUG(dbgs() << "LV: Found a runtime check ptr:" << *V <<"\n");
} else {
CanDoRT = false;
@ -2706,7 +2711,9 @@ bool LoopVectorizationLegality::canVectorizeMemory() {
// Check that we did not collect too many pointers or found a
// unsizeable pointer.
if (!CanDoRT || PtrRtCheck.Pointers.size() > RuntimeMemoryCheckThreshold) {
unsigned NumComparisons = (NumWritePtrs * (NumReadPtrs + NumWritePtrs - 1));
DEBUG(dbgs() << "LV: We need to compare " << NumComparisons << " ptrs.\n");
if (!CanDoRT || NumComparisons > RuntimeMemoryCheckThreshold) {
PtrRtCheck.reset();
CanDoRT = false;
}