ShortestPathAnalysis::Weight ShortestPathAnalysis::
getWeight(SILBasicBlock *BB, Weight CallerWeight) {
assert(BB->getParent() == F);
SILLoop *Loop = LI->getLoopFor(BB);
if (!Loop) {
// We are not in a loop. So just account the length of our function scope
// in to the length of the CallerWeight.
return Weight(CallerWeight.ScopeLength + getScopeLength(BB, 0),
CallerWeight.LoopWeight);
}
int LoopDepth = Loop->getLoopDepth();
// Deal with the corner case of having more than 4 nested loops.
while (LoopDepth >= MaxNumLoopLevels) {
--LoopDepth;
Loop = Loop->getParentLoop();
}
Weight W(getScopeLength(BB, LoopDepth), SingleLoopWeight);
// Add weights for all the loops BB is in.
while (Loop) {
assert(LoopDepth > 0);
BlockInfo *HeaderInfo = getBlockInfo(Loop->getHeader());
int InnerLoopLength = HeaderInfo->getScopeLength(LoopDepth) *
ShortestPathAnalysis::LoopCount;
int OuterLoopWeight = SingleLoopWeight;
int OuterScopeLength = HeaderInfo->getScopeLength(LoopDepth - 1);
// Reaching the outermost loop, we use the CallerWeight to get the outer
// length+loopweight.
if (LoopDepth == 1) {
// If the apply in the caller is not in a significant loop, just stop with
// what we have now.
if (CallerWeight.LoopWeight < 4)
return W;
// If this function is part of the caller's scope length take the caller's
// scope length. Note: this is not the case e.g. if the apply is in a
// then-branch of an if-then-else in the caller and the else-branch is
// the short path.
if (CallerWeight.ScopeLength > OuterScopeLength)
OuterScopeLength = CallerWeight.ScopeLength;
OuterLoopWeight = CallerWeight.LoopWeight;
}
assert(OuterScopeLength >= InnerLoopLength);
// If the current loop is only a small part of its outer loop, we don't
// take the outer loop that much into account. Only if the current loop is
// actually the "main part" in the outer loop we add the full loop weight
// for the outer loop.
if (OuterScopeLength < InnerLoopLength * 2) {
W.LoopWeight += OuterLoopWeight - 1;
} else if (OuterScopeLength < InnerLoopLength * 3) {
W.LoopWeight += OuterLoopWeight - 2;
} else if (OuterScopeLength < InnerLoopLength * 4) {
W.LoopWeight += OuterLoopWeight - 3;
} else {
return W;
}
--LoopDepth;
Loop = Loop->getParentLoop();
}
assert(LoopDepth == 0);
return W;
}
