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CopyForwarding cleanup, and add a check for alloc_stack after copy_addr (NFC, disabled).

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Swift SVN r22288
This commit is contained in:
Andrew Trick
2014-09-25 20:59:33 +00:00
parent e0afb13abb
commit 149abe164d
1 changed files with 46 additions and 40 deletions
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84
lib/SILPasses/CopyForwarding.cpp
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@@ -192,23 +192,24 @@ public:
void forwardCopiesOf(SILValue Def, SILFunction *F);
protected:
bool checkUsers();
bool collectUsers();
bool propagateCopy(CopyAddrInst *CopyInst);
bool forwardPropagateCopy(CopyAddrInst *CopyInst);
bool backwardPropagateCopy(CopyAddrInst *CopyInst);
bool forwardPropagateCopy(CopyAddrInst *CopyInst,
SmallPtrSetImpl<SILInstruction*> &DestUserInsts);
bool backwardPropagateCopy(CopyAddrInst *CopyInst,
SmallPtrSetImpl<SILInstruction*> &DestUserInsts);
bool hoistDestroy(SILInstruction *DestroyPoint, SILLocation DestroyLoc);
};
} // namespace
/// Visit all uses of CurrentDef. Return false if any unsafe uses are found.
/// Safe uses are those that access the CurrentDef without capturing or exposing
/// it to any other instructions.
/// Gather all instructions that use CurrentDef.
/// - DestroyPoints records 'destroy'
/// - TakePoints records 'copy_addr [take] src'
/// - SrcUserInsts records other users.
///
/// As a side-effect, record DestroyPoints and TakePoints.
///
/// TODO: This should be guaranteed to return true if we can assume that
/// address-only types are always accessed by-value.
bool CopyForwarding::checkUsers() {
/// If we are unable to find all uses, for example, because we don't look
/// through struct_element_addr, then return false.
bool CopyForwarding::collectUsers() {
for (auto UI : CurrentDef.getUses()) {
SILInstruction *UserInst = UI->getUser();
if (auto *Apply = dyn_cast<ApplyInst>(UserInst)) {
@@ -254,18 +255,29 @@ bool CopyForwarding::checkUsers() {
return true;
}
/// If the copy's dest is an @out argument, make no attempt to forward
/// propagate, because it will fail.
/// Attempt to forward, then backward propagation this copy.
bool CopyForwarding::propagateCopy(CopyAddrInst *CopyInst) {
SILValue CopyDest = CopyInst->getDest();
if (!isa<SILArgument>(CopyDest.getDef()))
if (forwardPropagateCopy(CopyInst))
SILBasicBlock *BB = CopyInst->getParent();
// Gather a list of CopyDest users in this block.
SmallPtrSet<SILInstruction*, 16> DestUserInsts;
for (auto UI : CopyDest.getUses()) {
SILInstruction *UserInst = UI->getUser();
if (UserInst != CopyInst && UI->getUser()->getParent() == BB)
DestUserInsts.insert(UI->getUser());
}
// Note that DestUserInsts is likely empty when the dest is an 'out' argument,
// allowing to go straight to backward propagation.
if (forwardPropagateCopy(CopyInst, DestUserInsts))
return true;
return backwardPropagateCopy(CopyInst);
// Forward propagation failed. Attempt to backward propagate.
return backwardPropagateCopy(CopyInst, DestUserInsts);
}
/// Perform copy-propagation. Find a set of uses that the given copy can forward
/// to and replace them with the copy's source.
/// Perform forward copy-propagation. Find a set of uses that the given copy can
/// forward to and replace them with the copy's source.
///
/// We must only replace uses of this copy's value. To do this, we search
/// forward in the current block from the copy that initializes the value to the
@@ -283,15 +295,15 @@ bool CopyForwarding::propagateCopy(CopyAddrInst *CopyInst) {
/// TODO: If the copy's dest is an @out argument, or if we fail to find a deinit
/// in the local scan, then propagate backward instead of forward by rewriting
/// the copy source's reaching "init" to initialize the copy's dest instead.
bool CopyForwarding::forwardPropagateCopy(CopyAddrInst *CopyInst) {
bool CopyForwarding::forwardPropagateCopy(
CopyAddrInst *CopyInst,
SmallPtrSetImpl<SILInstruction*> &DestUserInsts) {
if (DestUserInsts.empty())
return false;
SILValue CopyDest = CopyInst->getDest();
SILBasicBlock *BB = CopyInst->getParent();
// Gather a list of CopyDest users in this block.
SmallPtrSet<SILInstruction*, 16> DestUserInsts;
for (auto UI : CopyDest.getUses()) {
if (UI->getUser()->getParent() == BB)
DestUserInsts.insert(UI->getUser());
}
// Scan forward recording all operands that use CopyDest until we see the
// next deinit of CopyDest.
SmallVector<Operand*, 16> ValueUses;
@@ -337,20 +349,14 @@ bool CopyForwarding::forwardPropagateCopy(CopyAddrInst *CopyInst) {
return true;
}
bool CopyForwarding::backwardPropagateCopy(CopyAddrInst *CopyInst) {
// FIXME: unimplemented. scan backward until we find all reaching
// inits. Replace all references to the copy's source with the copy's dest.
bool CopyForwarding::backwardPropagateCopy(
CopyAddrInst *CopyInst,
SmallPtrSetImpl<SILInstruction*> &DestUserInsts) {
DEBUG(llvm::dbgs() << " Backward propagating " << *CopyInst);
SILValue CopySrc = CopyInst->getSrc();
SILValue CopyDest = CopyInst->getDest();
SILBasicBlock *BB = CopyInst->getParent();
// Gather a list of CopyDest users in this block.
SmallPtrSet<SILInstruction*, 16> DestUserInsts;
for (auto UI : CopyDest.getUses()) {
if (UI->getUser()->getParent() == BB)
DestUserInsts.insert(UI->getUser());
}
ValueBase *CopyDestDef = CopyInst->getDest().getDef();
// Scan backward recording all operands that use CopySrc until we see the
// most recent init of CopySrc.
@@ -361,7 +367,7 @@ bool CopyForwarding::backwardPropagateCopy(CopyAddrInst *CopyInst) {
--SI;
// If we see another use of Dest, then the dest location is deinitialized
// after the Src location is initialized. So we really need the copy.
if (DestUserInsts.count(&*SI)) {
if (DestUserInsts.count(&*SI) || &*SI == CopyDestDef) {
DEBUG(llvm::dbgs() << " Skipping copy " << *CopyInst
<< ", dest used by " << *SI);
return false;
@@ -465,7 +471,7 @@ void CopyForwarding::forwardCopiesOf(SILValue Def, SILFunction *F) {
reset();
CurrentDef = Def;
DEBUG(llvm::dbgs() << "Analyzing copies of Def: " << Def);
if (!checkUsers())
if (!collectUsers())
return;
// First forward any copies that implicitly destroy CurrentDef. There is no