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SIL passes: Work with select_enum instead of enum_is_tag.

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Simplify binary switches to select_enum instead of enum_is_tag, and make a first attempt at changing passes over to recognize limited forms of select_enum instead of enum_is_tag. There is one case in test/SILPasses/simplify_cfg.sil I wasn't able to figure out, and there are a lot more general passes we could define in terms of select_enum.

Swift SVN r22615
This commit is contained in:
Joe Groff
2014-10-09 03:49:31 +00:00
parent d4316bd302
commit c2fc9f58b8
15 changed files with 397 additions and 165 deletions
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53
lib/SILPasses/SILCodeMotion.cpp
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@@ -474,23 +474,30 @@ static bool tryToSinkRefCountAcrossSwitch(SwitchEnumInst *Switch,
return true;
}
/// Sink retain_value, release_value before enum_is_tag to be retain_value,
/// Sink retain_value, release_value before select_enum to be retain_value,
/// release_value on the payload of the switch_enum in the destination BBs. We
/// only do this if the destination BBs have only the switch enum as its
/// predecessor.
static bool tryToSinkRefCountAcrossEnumIsTag(CondBranchInst *CondBr,
SILBasicBlock::iterator I,
AliasAnalysis *AA) {
static bool tryToSinkRefCountAcrossSelectEnum(CondBranchInst *CondBr,
SILBasicBlock::iterator I,
AliasAnalysis *AA) {
// If this instruction is not a retain_value, there is nothing left for us to
// do... bail...
if (!isa<RetainValueInst>(I))
return false;
// Make sure the condition comes from an enum_is_tag
auto *EITI = dyn_cast<EnumIsTagInst>(CondBr->getCondition());
if (!EITI)
// Make sure the condition comes from a select_enum
auto *SEI = dyn_cast<SelectEnumInst>(CondBr->getCondition());
if (!SEI)
return false;
// Try to find a single literal "true" case.
// TODO: More general conditions in which we can relate the BB to a single
// case, such as when there's a single literal "false" case.
EnumElementDecl *TrueElement = SEI->getSingleTrueElement();
if (!TrueElement)
return false;
// Next go over all instructions after I in the basic block. If none of them
// can decrement our ptr value, we can move the retain over the ref count
// inst. If any of them do potentially decrement the ref count of Ptr, we can
@@ -505,14 +512,14 @@ static bool tryToSinkRefCountAcrossEnumIsTag(CondBranchInst *CondBr,
// If the retain value's argument is not the cond_br's argument, we can't do
// anything with our simplistic analysis... bail...
if (Ptr != EITI->getOperand())
if (Ptr != SEI->getEnumOperand())
return false;
// Work out which enum element is the true branch, and which is false.
// If the enum only has 2 values and its tag isn't the true branch, then we
// know the true branch must be the other tag.
EnumElementDecl *Elts[2] = {EITI->getElement(), nullptr};
EnumDecl *E = EITI->getOperand().getType().getEnumOrBoundGenericEnum();
EnumElementDecl *Elts[2] = {TrueElement, nullptr};
EnumDecl *E = SEI->getEnumOperand().getType().getEnumOrBoundGenericEnum();
if (!E)
return false;
@@ -520,7 +527,7 @@ static bool tryToSinkRefCountAcrossEnumIsTag(CondBranchInst *CondBr,
EnumElementDecl *OtherElt = nullptr;
for (EnumElementDecl *Elt : E->getAllElements()) {
// Skip the case where we find the enum_is_tag element
if (Elt == EITI->getElement())
if (Elt == TrueElement)
continue;
// If we find another element, then we must have more than 2, so bail.
if (OtherElt)
@@ -534,7 +541,7 @@ static bool tryToSinkRefCountAcrossEnumIsTag(CondBranchInst *CondBr,
Elts[1] = OtherElt;
SILBuilder Builder(EITI);
SILBuilder Builder(SEI);
// Ok, we have a ref count instruction, sink it!
for (unsigned i = 0; i != 2; ++i) {
@@ -568,7 +575,7 @@ static bool tryToSinkRefCountInst(SILBasicBlock::iterator T,
// enum_is_tag, we may be able to sink anyways. So we do not return on a
// failure case.
if (auto *CondBr = dyn_cast<CondBranchInst>(T))
if (tryToSinkRefCountAcrossEnumIsTag(CondBr, I, AA))
if (tryToSinkRefCountAcrossSelectEnum(CondBr, I, AA))
return true;
}
@@ -736,7 +743,7 @@ public:
bool sinkIncrementsOutOfSwitchRegions(AliasAnalysis *AA,
RCIdentityAnalysis *RCIA);
void handlePredSwitchEnum(SwitchEnumInst *S);
void handlePredCondEnumIsTag(CondBranchInst *CondBr);
void handlePredCondSelectEnum(CondBranchInst *CondBr);
/// Helper method which initializes this state map with the data from the
/// first predecessor BB.
@@ -824,20 +831,24 @@ void BBEnumTagDataflowState::handlePredSwitchEnum(SwitchEnumInst *S) {
"the switch_enum.");
}
void BBEnumTagDataflowState::handlePredCondEnumIsTag(CondBranchInst *CondBr) {
void BBEnumTagDataflowState::handlePredCondSelectEnum(CondBranchInst *CondBr) {
EnumIsTagInst *EITI = dyn_cast<EnumIsTagInst>(CondBr->getCondition());
SelectEnumInst *EITI = dyn_cast<SelectEnumInst>(CondBr->getCondition());
if (!EITI)
return;
auto TrueElement = EITI->getSingleTrueElement();
if (!TrueElement)
return;
// Find the tag associated with our BB and set the state of the
// enum we switch on to that value. This is important so we can determine
// covering switches for enums that have cases without payload.
// Check if we are the true case, ie, we know that we are the given tag.
const auto &Operand = EITI->getOperand();
const auto &Operand = EITI->getEnumOperand();
if (CondBr->getTrueBB() == getBB()) {
ValueToCaseMap[Operand] = EITI->getElement();
ValueToCaseMap[Operand] = TrueElement;
return;
}
@@ -848,7 +859,7 @@ void BBEnumTagDataflowState::handlePredCondEnumIsTag(CondBranchInst *CondBr) {
EnumElementDecl *OtherElt = nullptr;
for (EnumElementDecl *Elt : E->getAllElements()) {
// Skip the case where we find the enum_is_tag element
if (Elt == EITI->getElement())
if (Elt == TrueElement)
continue;
// If we find another element, then we must have more than 2, so bail.
if (OtherElt)
@@ -911,7 +922,7 @@ mergeSinglePredTermInfoIntoState(BBToDataflowStateMap &BBToStateMap,
if (!CondBr)
return;
handlePredCondEnumIsTag(CondBr);
handlePredCondSelectEnum(CondBr);
}
void