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[LoopAccesses] Add canAnalyzeLoop

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This allows the analysis to be attempted with any loop.  This feature
will be used with -analysis.  (LV only requests the analysis on loops
that have already satisfied these tests.)

This is part of the patchset that converts LoopAccessAnalysis into an
actual analysis pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229895 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Adam Nemet 2015-02-19 19:15:10 +00:00
parent 9fdb32eb84
commit 5c4c262b3c
2 changed files with 55 additions and 1 deletions
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4
include/llvm/Analysis/LoopAccessAnalysis.h
View File

@ -181,6 +181,10 @@ private:
/// \brief Analyze the loop. Substitute symbolic strides using Strides.
void analyzeLoop(ValueToValueMap &Strides);
/// \brief Check if the structure of the loop allows it to be analyzed by this
/// pass.
bool canAnalyzeLoop();
void emitAnalysis(VectorizationReport &Message);
/// We need to check that all of the pointers in this list are disjoint

52
lib/Analysis/LoopAccessAnalysis.cpp
View File

@ -855,6 +855,55 @@ bool MemoryDepChecker::areDepsSafe(AccessAnalysis::DepCandidates &AccessSets,
return true;
}
bool LoopAccessInfo::canAnalyzeLoop() {
// We can only analyze innermost loops.
if (!TheLoop->empty()) {
emitAnalysis(VectorizationReport() << "loop is not the innermost loop");
return false;
}
// We must have a single backedge.
if (TheLoop->getNumBackEdges() != 1) {
emitAnalysis(
VectorizationReport() <<
"loop control flow is not understood by analyzer");
return false;
}
// We must have a single exiting block.
if (!TheLoop->getExitingBlock()) {
emitAnalysis(
VectorizationReport() <<
"loop control flow is not understood by analyzer");
return false;
}
// We only handle bottom-tested loops, i.e. loop in which the condition is
// checked at the end of each iteration. With that we can assume that all
// instructions in the loop are executed the same number of times.
if (TheLoop->getExitingBlock() != TheLoop->getLoopLatch()) {
emitAnalysis(
VectorizationReport() <<
"loop control flow is not understood by analyzer");
return false;
}
// We need to have a loop header.
DEBUG(dbgs() << "LAA: Found a loop: " <<
TheLoop->getHeader()->getName() << '\n');
// ScalarEvolution needs to be able to find the exit count.
const SCEV *ExitCount = SE->getBackedgeTakenCount(TheLoop);
if (ExitCount == SE->getCouldNotCompute()) {
emitAnalysis(VectorizationReport() <<
"could not determine number of loop iterations");
DEBUG(dbgs() << "LAA: SCEV could not compute the loop exit count.\n");
return false;
}
return true;
}
void LoopAccessInfo::analyzeLoop(ValueToValueMap &Strides) {
typedef SmallVector<Value*, 16> ValueVector;
@ -1238,7 +1287,8 @@ LoopAccessInfo::LoopAccessInfo(Loop *L, ScalarEvolution *SE,
DominatorTree *DT, ValueToValueMap &Strides)
: TheLoop(L), SE(SE), DL(DL), TLI(TLI), AA(AA), DT(DT), NumLoads(0),
NumStores(0), MaxSafeDepDistBytes(-1U), CanVecMem(false) {
analyzeLoop(Strides);
if (canAnalyzeLoop())
analyzeLoop(Strides);
}
LoopAccessInfo &LoopAccessAnalysis::getInfo(Loop *L, ValueToValueMap &Strides) {