1+ // ===--- SILGenLocalArchetype.cpp - Local archetype transform -------------===//
2+ //
3+ // This source file is part of the Swift.org open source project
4+ //
5+ // Copyright (c) 2024 Apple Inc. and the Swift project authors
6+ // Licensed under Apache License v2.0 with Runtime Library Exception
7+ //
8+ // See https://swift.org/LICENSE.txt for license information
9+ // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
10+ //
11+ // ===----------------------------------------------------------------------===//
12+ //
13+ // This file implements the transformation which rewrites captured local
14+ // archetypes into primary archetypes in the enclosing function's generic
15+ // signature.
16+ //
17+ // ===----------------------------------------------------------------------===//
18+
19+ #include " SILGen.h"
20+ #include " swift/AST/LocalArchetypeRequirementCollector.h"
21+ #include " swift/SIL/SILInstruction.h"
22+ #include " swift/SIL/SILCloner.h"
23+
24+ using namespace swift ;
25+ using namespace swift ::Lowering;
26+
27+ namespace {
28+
29+ class LocalArchetypeTransform : public SILCloner <LocalArchetypeTransform> {
30+ friend class SILCloner <LocalArchetypeTransform>;
31+ friend class SILInstructionVisitor <LocalArchetypeTransform>;
32+
33+ GenericSignatureWithCapturedEnvironments sig;
34+ GenericEnvironment *env;
35+
36+ public:
37+ LocalArchetypeTransform (SILFunction *F,
38+ GenericSignatureWithCapturedEnvironments sig)
39+ : SILCloner(*F), env(sig.genericSig.getGenericEnvironment()) {
40+
41+ assert (!sig.capturedEnvs .empty () && " Why are we doing this?"
42+
43+ // The primary archetypes of the old generic environment map to
44+ // primary archetypes of the new generic environment at the same
45+ // index and depth.
46+ Functor.SubsMap = env->getForwardingSubstitutionMap ();
47+
48+ // Local archetypes map to generic parameters at higher depths.
49+ MapLocalArchetypesOutOfContext mapOutOfContext (sig.baseGenericSig ,
50+ sig.capturedEnvs );
51+
52+ // For each captured environment...
53+ for (auto *capturedEnv : sig.capturedEnvs ) {
54+ // For each introduced generic parameter...
55+ auto localParams = capturedEnv->getGenericSignature ()
56+ .getInnermostGenericParams ();
57+ for (auto *gp : localParams) {
58+ // Get the local archetype from the captured environment.
59+ auto origArchetypeTy = capturedEnv->mapTypeIntoContext (gp)
60+ ->castTo <LocalArchetypeType>();
61+
62+ // Map the local archetype to an interface type in the new generic
63+ // signature.
64+ auto substInterfaceTy = mapOutOfContext (origArchetypeTy);
65+
66+ // Map this interface type into the new generic environment to get
67+ // a primary archetype.
68+ auto substArchetypeTy = env->mapTypeIntoContext (substInterfaceTy)
69+ ->
castTo <PrimaryArchetypeType>();
70+
71+ // Remember this correspondence.
72+ registerLocalArchetypeRemapping (origArchetypeTy, substArchetypeTy);
73+ }
74+ }
75+ }
76+
77+ void doIt () {
78+ auto &F = getBuilder ().getFunction ();
79+
80+ // Collect the old basic blocks that we're going to delete.
81+ llvm::SmallVector<SILBasicBlock *, 4 > bbs;
82+ for (auto &bb : F)
83+ bbs.push_back (&bb);
84+
85+ // Make F.mapTypeIntoContext() use the new environment.
86+ F.setGenericEnvironment (env);
87+
88+ // Start by cloning the entry block.
89+ auto *origEntryBlock = F.getEntryBlock ();
90+ auto *clonedEntryBlock = F.createBasicBlock ();
91+
92+ // Clone arguments.
93+ SmallVector<SILValue, 4 > entryArgs;
94+ entryArgs.reserve (origEntryBlock->getArguments ().size ());
95+ for (auto &origArg : origEntryBlock->getArguments ()) {
96+
97+ // Remap the argument type into the new generic environment.
98+ SILType mappedType = remapType (origArg->getType ());
99+ auto *NewArg = clonedEntryBlock->createFunctionArgument (
100+ mappedType, origArg->getDecl (), true );
101+ NewArg->copyFlags (cast<SILFunctionArgument>(origArg));
102+ entryArgs.push_back (NewArg);
103+ }
104+
105+ // Clone the remaining body.
106+ getBuilder ().setInsertionPoint (clonedEntryBlock);
107+ cloneFunctionBody (&F, clonedEntryBlock, entryArgs,
108+ true /* replaceOriginalFunctionInPlace*/
109+
110+ // Insert the new entry block at the beginning.
111+ F.moveBlockBefore (clonedEntryBlock, F.begin ());
112+
113+ // FIXME: This should be a common utility.
114+
115+ // Erase the old basic blocks.
116+ for (auto *bb : bbs) {
117+ for (SILArgument *arg : bb->getArguments ()) {
118+ arg->replaceAllUsesWithUndef ();
119+ // To appease the ownership verifier, just set to None.
120+ arg->setOwnershipKind (OwnershipKind::None);
121+ }
122+
123+ // Instructions in the dead block may be used by other dead blocks. Replace
124+ // any uses of them with undef values.
125+ while (!bb->empty ()) {
126+ // Grab the last instruction in the bb.
127+ auto *inst = &bb->back ();
128+
129+ // Replace any still-remaining uses with undef values and erase.
130+ inst->replaceAllUsesOfAllResultsWithUndef ();
131+ inst->eraseFromParent ();
132+ }
133+
134+ // Finally, erase the basic block itself.
135+ bb->eraseFromParent ();
136+ }
137+ }
138+ };
139+
140+ } // end anonymous namespace
141+
142+ void SILGenModule::recontextualizeCapturedLocalArchetypes (
143+ SILFunction *F, GenericSignatureWithCapturedEnvironments sig) {
144+ if (sig.capturedEnvs .empty ())
145+ return ;
146+
147+ LocalArchetypeTransform (F, sig).doIt ();
148+ }
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