[LoopAccesses] Add canAnalyzeLoop
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.
llvm-svn: 229895
diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
index 0591703..40b70ef 100644
--- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp
+++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp
@@ -855,6 +855,55 @@
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 @@
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) {