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[RS4GC] Cleanup meetBDVState. NFC.

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meetBDVState looks pretty difficult to read and follow.
This is purely NFC but doing several things:

1) Combine meet and meetBDVState
2) Move the function to be a member of BDVState
3) Make BDVState be a mutable object
4) Convert switch to sequence of ifs
5) Adds comments.

Reviewers: reames, dantrushin
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D99064
This commit is contained in:
Serguei Katkov 2021-04-09 10:20:25 +07:00
parent 58e3420193
commit 1ad2b950e9
1 changed files with 35 additions and 39 deletions
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74
lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
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@ -706,6 +706,39 @@ public:
bool isUnknown() const { return getStatus() == Unknown; }
bool isConflict() const { return getStatus() == Conflict; }
// Values of type BDVState form a lattice, and this function implements the
// meet
// operation.
void meet(const BDVState &Other) {
auto markConflict = [&]() {
Status = BDVState::Conflict;
BaseValue = nullptr;
};
// Conflict is a final state.
if (isConflict())
return;
// if we are not known - just take other state.
if (isUnknown()) {
Status = Other.getStatus();
BaseValue = Other.getBaseValue();
return;
}
// We are base.
assert(isBase() && "Unknown state");
// If other is unknown - just keep our state.
if (Other.isUnknown())
return;
// If other is conflict - it is a final state.
if (Other.isConflict())
return markConflict();
// Other is base as well.
assert(Other.isBase() && "Unknown state");
// If bases are different - Conflict.
if (getBaseValue() != Other.getBaseValue())
return markConflict();
// We are identical, do nothing.
}
bool operator==(const BDVState &Other) const {
return OriginalValue == OriginalValue && BaseValue == Other.BaseValue &&
Status == Other.Status;
@ -751,43 +784,6 @@ static raw_ostream &operator<<(raw_ostream &OS, const BDVState &State) {
}
#endif
static BDVState::StatusTy meet(const BDVState::StatusTy &LHS,
const BDVState::StatusTy &RHS) {
switch (LHS) {
case BDVState::Unknown:
return RHS;
case BDVState::Base:
switch (RHS) {
case BDVState::Unknown:
case BDVState::Base:
return BDVState::Base;
case BDVState::Conflict:
return BDVState::Conflict;
};
llvm_unreachable("covered switch");
case BDVState::Conflict:
return BDVState::Conflict;
}
llvm_unreachable("covered switch");
}
// Values of type BDVState form a lattice, and this function implements the meet
// operation.
static BDVState meetBDVState(const BDVState &LHS, const BDVState &RHS) {
auto NewStatus = meet(LHS.getStatus(), RHS.getStatus());
assert(NewStatus == meet(RHS.getStatus(), LHS.getStatus()));
Value *BaseValue = LHS.getStatus() == BDVState::Base ?
LHS.getBaseValue() : RHS.getBaseValue();
if (LHS.getStatus() == BDVState::Base && RHS.getStatus() == BDVState::Base &&
LHS.getBaseValue() != RHS.getBaseValue()) {
NewStatus = BDVState::Conflict;
}
if (NewStatus == BDVState::Conflict)
BaseValue = nullptr;
return BDVState(LHS.getOriginalValue(), NewStatus, BaseValue);
}
/// For a given value or instruction, figure out what base ptr its derived from.
/// For gc objects, this is simply itself. On success, returns a value which is
/// the base pointer. (This is reliable and can be used for relocation.) On
@ -971,10 +967,10 @@ static Value *findBasePointer(Value *I, DefiningValueMapTy &Cache) {
"why did it get added?");
BDVState NewState(BDV);
visitBDVOperands(BDV, [&] (Value *Op) {
visitBDVOperands(BDV, [&](Value *Op) {
Value *BDV = findBaseOrBDV(Op, Cache);
auto OpState = GetStateForBDV(BDV, Op);
NewState = meetBDVState(NewState, OpState);
NewState.meet(OpState);
});
BDVState OldState = States[BDV];