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OSSA: CheckedCastBrJumpThreading: support using RAUW utility.
Begin adding support for OSSA to checked-cast jump-threading based on the new ownership utilities. TODO: Finish migrating to the new utilities in OwnershipOptUtils. Ensure full unit test coverage.
This commit is contained in:
Andrew Trick
@@ -18,6 +18,7 @@
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#include "swift/SILOptimizer/Utils/BasicBlockOptUtils.h"
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#include "swift/SILOptimizer/Utils/CFGOptUtils.h"
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#include "swift/SILOptimizer/Utils/InstOptUtils.h"
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#include "swift/SILOptimizer/Utils/OwnershipOptUtils.h"
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#include "swift/SILOptimizer/Utils/SILInliner.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/SmallVector.h"
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@@ -52,6 +53,11 @@ class CheckedCastBrJumpThreading {
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// Enable non-trivial terminator rewriting in OSSA.
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bool EnableOSSARewriteTerminator;
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InstModCallbacks callbacks;
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// Shared data structures across OwnershipRAUWHelper instances.
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OwnershipFixupContext rauwContext;
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// List of predecessors.
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typedef SmallVector<SILBasicBlock *, 8> PredList;
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@@ -82,8 +88,10 @@ class CheckedCastBrJumpThreading {
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// Copy of CheckedCastBrJumpThreading::FailurePreds.
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PredList FailurePreds;
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// The argument of the dominating checked_cast_br's successor block.
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SILValue SuccessArg;
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SILPhiArgument *SuccessArg;
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// True if the dominating check is inverted AND all the predecessors are on
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// the dominating check's success path.
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bool InvertSuccess;
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// True if CheckedCastBrJumpThreading::numUnknownPreds is not 0.
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@@ -92,13 +100,16 @@ class CheckedCastBrJumpThreading {
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Edit(SILBasicBlock *CCBBlock, bool InvertSuccess,
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const PredList &SuccessPreds,
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const PredList &FailurePreds,
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bool hasUnknownPreds, SILValue SuccessArg) :
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bool hasUnknownPreds, SILPhiArgument *SuccessArg) :
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CCBBlock(CCBBlock), SuccessPreds(SuccessPreds), FailurePreds(FailurePreds),
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SuccessArg(SuccessArg), InvertSuccess(InvertSuccess),
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hasUnknownPreds(hasUnknownPreds) { }
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bool canRAUW(OwnershipFixupContext &rauwContext);
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void modifyCFGForFailurePreds(BasicBlockCloner &Cloner);
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void modifyCFGForSuccessPreds(BasicBlockCloner &Cloner);
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void modifyCFGForSuccessPreds(BasicBlockCloner &Cloner,
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OwnershipFixupContext &rauwContext);
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};
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// Contains an entry for each checked_cast_br to be optimized.
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@@ -135,6 +146,7 @@ public:
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bool EnableOSSARewriteTerminator)
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: Fn(Fn), DT(DT), deBlocks(deBlocks),
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EnableOSSARewriteTerminator(EnableOSSARewriteTerminator),
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rauwContext(callbacks, *deBlocks),
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BlocksForWorklist(BlocksForWorklist), BlocksToEdit(Fn),
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BlocksToClone(Fn) {}
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@@ -238,8 +250,54 @@ SILValue CheckedCastBrJumpThreading::isArgValueEquivalentToCondition(
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}
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}
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/// Create a copy of the BB as a landing BB
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/// for all FailurePreds.
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// Return false if an ownership RAUW is necessary but cannot be performed.
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bool CheckedCastBrJumpThreading::Edit::
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canRAUW(OwnershipFixupContext &rauwContext) {
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if (InvertSuccess || SuccessPreds.empty())
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return true;
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auto *ccbi = cast<CheckedCastBranchInst>(CCBBlock->getTerminator());
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auto *oldSuccessArg = ccbi->getSuccessBB()->getArgument(0);
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// Check the ownership validity of the RAUW transformation that will replace
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// oldSuccessArg with SuccessArg. This is valid iff it will be valid to
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// replace the new checked_cast_br. The new checked_cast_br will be in a
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// cloned block reachable from a subset of the original block's predecessors,
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// it will have equivalent operands. Checking the current uses is unnecessary,
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// because after cloning, the only use of the cloned checked_cast_br will be
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// a phi in the successor. It is always valid to replace a phi use, because
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// phi itself already guarantees that lifetime extends over its own uses.
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return OwnershipRAUWHelper::hasValidNonLexicalRAUWOwnership(oldSuccessArg,
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SuccessArg);
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}
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// Erase the checked_cast_br that terminates this block. The caller must replace
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// and erase the successful cast result.
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//
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// The checked_cast_br failure result's uses are replaced with the cast's
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// operand, and the block argument representing that result is deleted. Since
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// the checked_cast's uses now use its forwarded operand, they are still in
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// valid OSSA form, so this can be done before updateOSSAAfterCloning, which
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// doesn't need to know about the erased checked_cast.
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static void eraseCheckedCastBr(
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CheckedCastBranchInst *checkedCastBr,
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CheckedCastBranchInst::SuccessorPath successorIdx) {
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SILBuilderWithScope Builder(checkedCastBr);
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Builder.createBranch(checkedCastBr->getLoc(),
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checkedCastBr->getSuccessors()[successorIdx]);
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auto *successBB = checkedCastBr->getSuccessBB();
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assert(successBB->getNumArguments() == 1);
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assert(successBB->getArgument(0)->use_empty());
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successBB->eraseArgument(0);
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if (checkedCastBr->getFunction()->hasOwnership()) {
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auto *failureBB = checkedCastBr->getFailureBB();
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assert(failureBB->getNumArguments() == 1);
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failureBB->getArgument(0)->replaceAllUsesWith(checkedCastBr->getOperand());
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failureBB->eraseArgument(0);
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}
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checkedCastBr->eraseFromParent();
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}
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void CheckedCastBrJumpThreading::Edit::modifyCFGForFailurePreds(
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BasicBlockCloner &Cloner) {
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if (FailurePreds.empty())
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@@ -248,12 +306,13 @@ void CheckedCastBrJumpThreading::Edit::modifyCFGForFailurePreds(
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assert(!Cloner.wasCloned());
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Cloner.cloneBlock();
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SILBasicBlock *TargetFailureBB = Cloner.getNewBB();
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// This cloned block branches to the FailureBB, so just delete the cast and
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// ignore the success target which will keep it's original predecessor.
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auto *clonedCCBI =
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cast<CheckedCastBranchInst>(TargetFailureBB->getTerminator());
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SILBuilderWithScope Builder(clonedCCBI);
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// This BB copy branches to the FailureBB.
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Builder.createBranch(clonedCCBI->getLoc(), clonedCCBI->getFailureBB());
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clonedCCBI->eraseFromParent();
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cast<CheckedCastBranchInst>(TargetFailureBB->getTerminator());
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auto *clonedSuccessArg = clonedCCBI->getSuccessBB()->getArgument(0);
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clonedSuccessArg->replaceAllUsesWithUndef();
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eraseCheckedCastBr(clonedCCBI, CheckedCastBranchInst::FailIdx);
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// Redirect all FailurePreds to the copy of BB.
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for (auto *Pred : FailurePreds) {
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@@ -262,62 +321,93 @@ void CheckedCastBrJumpThreading::Edit::modifyCFGForFailurePreds(
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replaceBranchTarget(TI, CCBBlock, TargetFailureBB,
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/*PreserveArgs=*/true);
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}
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Cloner.updateOSSAAfterCloning();
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}
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/// Create a copy of the BB or reuse BB as
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/// a landing basic block for all FailurePreds.
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/// Create a copy of the BB or reuse BB as a landing basic block for all
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/// FailurePreds.
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///
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/// Note: must be called after modifyCFGForFailurePreds and
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/// before modifyCFGForUnknownPreds.
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void CheckedCastBrJumpThreading::Edit::modifyCFGForSuccessPreds(
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BasicBlockCloner &Cloner) {
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BasicBlockCloner &Cloner, OwnershipFixupContext &rauwContext) {
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auto *checkedCastBr = cast<CheckedCastBranchInst>(CCBBlock->getTerminator());
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auto *oldSuccessArg = checkedCastBr->getSuccessBB()->getArgument(0);
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if (InvertSuccess) {
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auto *CCBI = cast<CheckedCastBranchInst>(CCBBlock->getTerminator());
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SILBuilderWithScope(CCBI).createBranch(CCBI->getLoc(),
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CCBI->getFailureBB());
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CCBI->eraseFromParent();
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assert(!hasUnknownPreds && "is not handled, should have been checked");
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// This success path is unused, so undef its uses and delete the cast.
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oldSuccessArg->replaceAllUsesWithUndef();
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eraseCheckedCastBr(checkedCastBr, CheckedCastBranchInst::FailIdx);
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return;
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}
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if (hasUnknownPreds) {
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if (!SuccessPreds.empty()) {
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// Create a copy of the BB as a landing BB.
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// for all SuccessPreds.
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assert(!Cloner.wasCloned());
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Cloner.cloneBlock();
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SILBasicBlock *TargetSuccessBB = Cloner.getNewBB();
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auto *clonedCCBI =
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cast<CheckedCastBranchInst>(TargetSuccessBB->getTerminator());
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SILBuilderWithScope Builder(clonedCCBI);
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// This BB copy branches to SuccessBB.
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// Take argument value from the dominating BB.
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Builder.createBranch(clonedCCBI->getLoc(), clonedCCBI->getSuccessBB(),
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{SuccessArg});
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clonedCCBI->eraseFromParent();
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if (!hasUnknownPreds) {
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// All predecessors are dominated by a successful cast. So the current BB
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// can be re-used instead as their target.
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//
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// NOTE: Assumes that failure predecessors have already been processed and
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// removed from the current block's predecessors.
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// Redirect all SuccessPreds to the copy of BB.
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for (auto *Pred : SuccessPreds) {
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TermInst *TI = Pred->getTerminator();
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// Replace branch to BB by branch to TargetSuccessBB.
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replaceBranchTarget(TI, CCBBlock, TargetSuccessBB, /*PreserveArgs=*/true);
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}
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}
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// Replace uses with SuccessArg from the dominating BB. Do this while it is
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// still a valid terminator result, before erasing the cast.
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OwnershipRAUWHelper rauwTransform(rauwContext, oldSuccessArg, SuccessArg);
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assert(rauwTransform.isValid() && "sufficiently checked by canRAUW");
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rauwTransform.perform();
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eraseCheckedCastBr(checkedCastBr, CheckedCastBranchInst::SuccessIdx);
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return;
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}
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// There are no predecessors where it is not clear
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// if they are dominated by a success or failure branch
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// of DomBB. Therefore, there is no need to clone
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// the BB for SuccessPreds. Current BB can be re-used
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// instead as their target.
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// Only clone if there are preds on the success path.
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if (SuccessPreds.empty())
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return;
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// Add an unconditional jump at the end of the block.
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// Take argument value from the dominating BB
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auto *CCBI = cast<CheckedCastBranchInst>(CCBBlock->getTerminator());
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SILBuilderWithScope(CCBI).createBranch(CCBI->getLoc(), CCBI->getSuccessBB(),
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{SuccessArg});
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CCBI->eraseFromParent();
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// Create a copy of the BB as a landing BB.
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// for all SuccessPreds.
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assert(!Cloner.wasCloned());
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Cloner.cloneBlock();
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SILBasicBlock *clonedCCBBlock = Cloner.getNewBB();
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// Redirect all SuccessPreds to the copy of BB.
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for (auto *Pred : SuccessPreds) {
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TermInst *TI = Pred->getTerminator();
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// Replace branch to BB by branch to TargetSuccessBB.
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replaceBranchTarget(TI, CCBBlock, clonedCCBBlock,
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/*PreserveArgs=*/true);
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}
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// Remove the unreachable checked_cast_br target.
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auto *clonedCCBI =
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cast<CheckedCastBranchInst>(clonedCCBBlock->getTerminator());
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auto *successBB = clonedCCBI->getSuccessBB();
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// This cloned block branches to the successBB.
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// The checked_cast_br uses are replaced with SuccessArg.
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if (!CCBBlock->getParent()->hasOwnership()) {
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SILBuilderWithScope Builder(clonedCCBI);
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Builder.createBranch(clonedCCBI->getLoc(), successBB, {SuccessArg});
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clonedCCBI->eraseFromParent();
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Cloner.updateOSSAAfterCloning();
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return;
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}
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// Remove all uses from the failure path so RAUW can erase the
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// terminator after replacing the successor argument.
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auto *failureBB = clonedCCBI->getFailureBB();
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assert(failureBB->getNumArguments() == 1 && "expecting term result");
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failureBB->getArgument(0)->replaceAllUsesWithUndef();
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// Create nested borrow scopes for new phis either created for the
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// checked_cast's results or during SSA update. This puts the SIL in
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// valid OSSA form before calling OwnershipRAUWHelper.
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Cloner.updateOSSAAfterCloning();
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auto *clonedSuccessArg = successBB->getArgument(0);
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OwnershipRAUWHelper rauwUtil(rauwContext, clonedSuccessArg, SuccessArg);
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assert(rauwUtil.isValid() && "sufficiently checked by canRAUW");
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rauwUtil.perform();
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eraseCheckedCastBr(clonedCCBI, CheckedCastBranchInst::SuccessIdx);
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}
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/// Handle a special case, where ArgBB is the entry block.
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bool CheckedCastBrJumpThreading::handleArgBBIsEntryBlock(SILBasicBlock *ArgBB,
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CheckedCastBranchInst *DomCCBI) {
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bool CheckedCastBrJumpThreading::handleArgBBIsEntryBlock(
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SILBasicBlock *ArgBB, CheckedCastBranchInst *DomCCBI) {
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if (!ArgBB->pred_empty())
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return false;
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@@ -644,7 +734,8 @@ bool CheckedCastBrJumpThreading::trySimplify(CheckedCastBranchInst *CCBI) {
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// Record what we want to change.
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Edit *edit = new (EditAllocator.Allocate())
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Edit(BB, InvertSuccess, SuccessPreds, FailurePreds,
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numUnknownPreds != 0, DomCCBI->getSuccessBB()->getArgument(0));
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numUnknownPreds != 0,
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cast<SILPhiArgument>(DomCCBI->getSuccessBB()->getArgument(0)));
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Edits.push_back(edit);
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return true;
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@@ -684,12 +775,15 @@ void CheckedCastBrJumpThreading::optimizeFunction() {
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if (!Cloner.canCloneBlock())
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continue;
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if (Fn->hasOwnership() && !edit->canRAUW(rauwContext))
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continue;
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// Create a copy of the BB as a landing BB
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// for all FailurePreds.
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edit->modifyCFGForFailurePreds(Cloner);
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// Create a copy of the BB or reuse BB as
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// a landing basic block for all SuccessPreds.
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edit->modifyCFGForSuccessPreds(Cloner);
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edit->modifyCFGForSuccessPreds(Cloner, rauwContext);
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if (Cloner.wasCloned()) {
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Cloner.updateOSSAAfterCloning();
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