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Tweaked RCIdentity comments during review.

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Swift SVN r25360
This commit is contained in:
Andrew Trick
2015-02-18 00:41:36 +00:00
parent cdb1ff6152
commit d6016759e7
1 changed files with 11 additions and 9 deletions
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20
lib/SILAnalysis/RCIdentityAnalysis.cpp
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@@ -112,6 +112,10 @@ static SILValue stripRCIdentityPreservingInsts(SILValue V) {
return SILValue();
}
/// V is the incoming value for the SILArgument A on at least one path. Find a
/// value that is trivially RC-identical to V and dominates the argument's
/// block. If such a value exists, it is a candidate for RC-indentity with the
/// argument itself--the caller must verify this after evaluating all paths.
SILValue RCIdentityAnalysis::stripOneRCIdentityIncomingValue(SILArgument *A,
SILValue V) {
// Strip off any non-argument instructions from IV. We know that this will
@@ -120,8 +124,7 @@ SILValue RCIdentityAnalysis::stripOneRCIdentityIncomingValue(SILArgument *A,
V = NewIV;
// Then make sure that this incoming value is from a BB which is different
// from our BB and dominates our BB. Otherwise, just return SILValue() there
// is nothing we can do hter.
// from our BB and dominates our BB. Otherwise, return SILValue() to bail.
DominanceInfo *DI = DA->getDomInfo(A->getFunction());
if (!dominatesArgument(DI, A, V))
return SILValue();
@@ -196,7 +199,7 @@ findDominatingNonPayloadedEdge(SILBasicBlock *IncomingEdgeBB,
// non-payloaded enums can always be eliminated (since we can always eliminate
// ref count operations on non-payloaded enums).
// RCIdentityBB must never have a non
// RCIdentityBB must have a valid dominator tree node.
auto *EndDomNode = DI->getNode(RCIdentityBB);
if (!EndDomNode)
return false;
@@ -325,14 +328,13 @@ stripRCIdentityPreservingArgs(SILValue V, unsigned RecursionDepth) {
return SILValue();
}
// Ok, we now know that all of our incoming values that are not no-payload
// enums are equal to FirstIV after just stripping RCIdentical instructions
// (*NOTE* not args). If we have no NonPayloadEnums, then we know that this
// Arg's RCIdentity must be FirstIV.
if (NoPayloadEnumBBs.empty())
// We now know that all incoming values, other than NoPayloadEnums, are
// FirstIV after trivially stripping RCIdentical instructions. If we have no
// NoPayloadEnums, then we know that this Arg's RCIdentity must be FirstIV.
if (NoPayloadEnums.empty())
return FirstIV;
// At this point, we know that we have *some* no-payload enums. If FirstIV is
// At this point, we know that we have *some* NoPayloadEnums. If FirstIV is
// not an enum, then we must bail. We do not try to analyze this case.
if (!FirstIV.getType().getEnumOrBoundGenericEnum())
return SILValue();