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Optimizer: enable SILCodeMotion in OSSA, but only for trivial values.

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to-do: we should eventually remove code motion of retain and release instructions and implement them as semantic ARC optimizations in OSSA.
This commit is contained in:
Erik Eckstein
2024-12-30 15:56:50 +01:00
parent 48b913af4b
commit 53d78abd01
3 changed files with 88 additions and 30 deletions
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66
lib/SILOptimizer/Transforms/SILCodeMotion.cpp
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@@ -27,6 +27,7 @@
#include "swift/SILOptimizer/PassManager/Passes.h"
#include "swift/SILOptimizer/PassManager/Transforms.h"
#include "swift/SILOptimizer/Utils/InstOptUtils.h"
#include "swift/SILOptimizer/Utils/OwnershipOptUtils.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/CommandLine.h"
@@ -917,6 +918,8 @@ static const int SinkSearchWindow = 6;
/// Returns True if we can sink this instruction to another basic block.
static bool canSinkInstruction(SILInstruction *Inst) {
if (hasOwnershipOperandsOrResults(Inst))
return false;
return !Inst->hasUsesOfAnyResult() && !isa<TermInst>(Inst);
}
@@ -1178,6 +1181,9 @@ static bool sinkArgument(EnumCaseDataflowContext &Context, SILBasicBlock *BB, un
if (!FSI || !hasOneNonDebugUse(FSI))
return false;
if (hasOwnershipOperandsOrResults(FSI))
return false;
// The list of identical instructions.
SmallVector<SingleValueInstruction *, 8> Clones;
Clones.push_back(FSI);
@@ -1743,38 +1749,43 @@ static bool processFunction(SILFunction *F, AliasAnalysis *AA,
LLVM_DEBUG(llvm::dbgs() << " Merging predecessors!\n");
State.mergePredecessorStates();
// If our predecessors cover any of our enum values, attempt to hoist
// releases up the CFG onto enum payloads or sink retains out of switch
// regions.
LLVM_DEBUG(llvm::dbgs() << " Attempting to move releases into "
"predecessors!\n");
if (!F->hasOwnership()) {
// If our predecessors cover any of our enum values, attempt to hoist
// releases up the CFG onto enum payloads or sink retains out of switch
// regions.
LLVM_DEBUG(llvm::dbgs() << " Attempting to move releases into "
"predecessors!\n");
// Perform a relatively local forms of retain sinking and release hoisting
// regarding switch regions and SILargument. This are not handled by retain
// release code motion.
if (HoistReleases) {
Changed |= State.hoistDecrementsIntoSwitchRegions(AA);
// Perform a relatively local forms of retain sinking and release hoisting
// regarding switch regions and SILargument. This are not handled by retain
// release code motion.
if (HoistReleases) {
Changed |= State.hoistDecrementsIntoSwitchRegions(AA);
}
// Sink switch related retains.
Changed |= sinkIncrementsIntoSwitchRegions(State.getBB(), AA, RCIA);
Changed |= State.sinkIncrementsOutOfSwitchRegions(AA, RCIA);
// Then attempt to sink code from predecessors. This can include retains
// which is why we always attempt to move releases up the CFG before sinking
// code from predecessors. We will never sink the hoisted releases from
// predecessors since the hoisted releases will be on the enum payload
// instead of the enum itself.
Changed |= canonicalizeRefCountInstrs(State.getBB());
}
// Sink switch related retains.
Changed |= sinkIncrementsIntoSwitchRegions(State.getBB(), AA, RCIA);
Changed |= State.sinkIncrementsOutOfSwitchRegions(AA, RCIA);
// Then attempt to sink code from predecessors. This can include retains
// which is why we always attempt to move releases up the CFG before sinking
// code from predecessors. We will never sink the hoisted releases from
// predecessors since the hoisted releases will be on the enum payload
// instead of the enum itself.
Changed |= canonicalizeRefCountInstrs(State.getBB());
Changed |= sinkCodeFromPredecessors(BBToStateMap, State.getBB());
Changed |= sinkArgumentsFromPredecessors(BBToStateMap, State.getBB());
Changed |= sinkLiteralsFromPredecessors(State.getBB());
// Try to hoist release of a SILArgument to predecessors.
Changed |= hoistSILArgumentReleaseInst(State.getBB());
// Then perform the dataflow.
LLVM_DEBUG(llvm::dbgs() << " Performing the dataflow!\n");
Changed |= State.process();
if (!F->hasOwnership()) {
// Try to hoist release of a SILArgument to predecessors.
Changed |= hoistSILArgumentReleaseInst(State.getBB());
// Then perform the dataflow.
LLVM_DEBUG(llvm::dbgs() << " Performing the dataflow!\n");
Changed |= State.process();
}
}
return Changed;
@@ -1791,9 +1802,6 @@ public:
/// The entry point to the transformation.
void run() override {
auto *F = getFunction();
// Skip functions with ownership for now.
if (F->hasOwnership())
return;
auto *AA = getAnalysis<AliasAnalysis>(F);
auto *PO = getAnalysis<PostOrderAnalysis>()->get(F);