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[NFC][SILOptimizer]: update outdated docs in DefiniteInit & DRY #83866

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Sep 22, 2025
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[NFC][SILOptimizer]: update outdated docs in DefiniteInit & DRY #83866

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33 changes: 15 additions & 18 deletions lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1114,8 +1114,7 @@ void LifetimeChecker::injectActorHops() {

void LifetimeChecker::doIt() {
// With any escapes tallied up, we can work through all the uses, checking
// for definitive initialization, promoting loads, rewriting assigns, and
// performing other tasks.
// for definitive initialization and performing other tasks.

// Note that this should not use a for-each loop, as the Uses list can grow
// and reallocate as we iterate over it.
Expand Down Expand Up @@ -1185,7 +1184,7 @@ void LifetimeChecker::doIt() {
}
}

// If we emitted an error, there is no reason to proceed with load promotion.
// If we emitted an error, there is no reason to proceed.
if (!EmittedErrorLocs.empty()) {
// Since we failed DI, for now, turn off the move checker on the entire
// function. With time, we should be able to allow for move checker checks
Expand Down Expand Up @@ -2512,8 +2511,8 @@ static void setStaticInitAccess(SILValue memoryAddress) {

/// updateInstructionForInitState - When an instruction being analyzed moves
/// from being InitOrAssign to some concrete state, update it for that state.
/// This includes rewriting them from assign instructions into their composite
/// operations.
/// This includes marking assign instructions so they will be appropriately
/// handled during RawSILInstLowering.
void LifetimeChecker::updateInstructionForInitState(unsigned UseID) {
DIMemoryUse &Use = Uses[UseID];
SILInstruction *Inst = Use.Inst;
Expand Down Expand Up @@ -2562,14 +2561,17 @@ void LifetimeChecker::updateInstructionForInitState(unsigned UseID) {
return; \
}
#include "swift/AST/ReferenceStorage.def"

// If this is an assign, rewrite it based on whether it is an initialization
// or not.
if (auto *AI = dyn_cast<AssignInst>(Inst)) {
// Remove this instruction from our data structures, since we will be
// removing it.

// Helper to remove the instruction from our data structures.
auto eraseUseInst = [&] {
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i couldn't resist hoisting this since it seemed like it was just copy-pasted over time... out of curiosity, why are the instructions removed from the Use/NonLoadUses structures in these cases?

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🤷

Use.Inst = nullptr;
llvm::erase_if(NonLoadUses[Inst], [&](unsigned id) { return id == UseID; });
};

// If this is an assign, mark it so that RawSILInstLowering can handle it
// appropriately.
if (auto *AI = dyn_cast<AssignInst>(Inst)) {
eraseUseInst();

if (TheMemory.isClassInitSelf() &&
Use.Kind == DIUseKind::SelfInit) {
Expand Down Expand Up @@ -2603,10 +2605,7 @@ void LifetimeChecker::updateInstructionForInitState(unsigned UseID) {
}

if (auto *AI = dyn_cast<AssignOrInitInst>(Inst)) {
// Remove this instruction from our data structures, since we will be
// removing it.
Use.Inst = nullptr;
llvm::erase_if(NonLoadUses[Inst], [&](unsigned id) { return id == UseID; });
eraseUseInst();

switch (Use.Kind) {
case DIUseKind::Assign:
Expand Down Expand Up @@ -3867,16 +3866,14 @@ static bool checkDefiniteInitialization(SILFunction &Fn) {

namespace {

/// Perform definitive initialization analysis and promote alloc_box uses into
/// SSA registers for later SSA-based dataflow passes.
/// Perform definitive initialization analysis.
class DefiniteInitialization : public SILFunctionTransform {
/// The entry point to the transformation.
void run() override {
// Don't rerun diagnostics on deserialized functions.
if (getFunction()->wasDeserializedCanonical())
return;

// Walk through and promote all of the alloc_box's that we can.
if (checkDefiniteInitialization(*getFunction())) {
invalidateAnalysis(SILAnalysis::InvalidationKind::FunctionBody);
}
Expand Down