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IRCE: only touch loops that have been shown to have a high 

backedge-taken count in profiliing data.

llvm-svn: 230619
This commit is contained in:
Sanjoy Das 2015-02-26 08:56:04 +00:00
parent e75ed92630
commit e91665de39
1 changed files with 17 additions and 4 deletions
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21
llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
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@ -82,6 +82,9 @@ static cl::opt<unsigned> LoopSizeCutoff("irce-loop-size-cutoff", cl::Hidden,
static cl::opt<bool> PrintChangedLoops("irce-print-changed-loops", cl::Hidden,
cl::init(false));
static cl::opt<int> MaxExitProbReciprocal("irce-max-exit-prob-reciprocal",
cl::Hidden, cl::init(10));
#define DEBUG_TYPE "irce"
namespace {
@ -441,7 +444,9 @@ struct LoopStructure {
return Result;
}
static Optional<LoopStructure> parseLoopStructure(ScalarEvolution &, Loop &,
static Optional<LoopStructure> parseLoopStructure(ScalarEvolution &,
BranchProbabilityInfo &BPI,
Loop &,
const char *&);
};
@ -615,8 +620,8 @@ static bool CanBeSMin(ScalarEvolution &SE, const SCEV *S) {
}
Optional<LoopStructure>
LoopStructure::parseLoopStructure(ScalarEvolution &SE, Loop &L,
const char *&FailureReason) {
LoopStructure::parseLoopStructure(ScalarEvolution &SE, BranchProbabilityInfo &BPI,
Loop &L, const char *&FailureReason) {
assert(L.isLoopSimplifyForm() && "should follow from addRequired<>");
BasicBlock *Latch = L.getLoopLatch();
@ -640,6 +645,14 @@ LoopStructure::parseLoopStructure(ScalarEvolution &SE, Loop &L,
unsigned LatchBrExitIdx = LatchBr->getSuccessor(0) == Header ? 1 : 0;
BranchProbability ExitProbability =
BPI.getEdgeProbability(LatchBr->getParent(), LatchBrExitIdx);
if (ExitProbability > BranchProbability(1, MaxExitProbReciprocal)) {
FailureReason = "short running loop, not profitable";
return None;
}
ICmpInst *ICI = dyn_cast<ICmpInst>(LatchBr->getCondition());
if (!ICI || !isa<IntegerType>(ICI->getOperand(0)->getType())) {
FailureReason = "latch terminator branch not conditional on integral icmp";
@ -1340,7 +1353,7 @@ bool InductiveRangeCheckElimination::runOnLoop(Loop *L, LPPassManager &LPM) {
const char *FailureReason = nullptr;
Optional<LoopStructure> MaybeLoopStructure =
LoopStructure::parseLoopStructure(SE, *L, FailureReason);
LoopStructure::parseLoopStructure(SE, BPI, *L, FailureReason);
if (!MaybeLoopStructure.hasValue()) {
DEBUG(dbgs() << "irce: could not parse loop structure: " << FailureReason
<< "\n";);