|
| 1 | +//===--- ScopeOptUtils.h --------------------------------------------------===// |
| 2 | +// |
| 3 | +// This source file is part of the Swift.org open source project |
| 4 | +// |
| 5 | +// Copyright (c) 2014 - 2021 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 | +/// A simple scope like construct for use in the SILOptimizer. |
| 14 | +/// |
| 15 | +//===----------------------------------------------------------------------===// |
| 16 | + |
| 17 | +#ifndef SWIFT_SILOPTIMIZER_UTILS_SCOPEOPTUTILS_H |
| 18 | +#define SWIFT_SILOPTIMIZER_UTILS_SCOPEOPTUTILS_H |
| 19 | + |
| 20 | +#include "swift/Basic/LLVM.h" |
| 21 | +#include "swift/SIL/SILBuilder.h" |
| 22 | +#include "swift/SIL/SILValue.h" |
| 23 | +#include "llvm/ADT/Optional.h" |
| 24 | +#include "llvm/ADT/SmallVector.h" |
| 25 | +#include <functional> |
| 26 | + |
| 27 | +namespace swift { |
| 28 | +namespace siloptimizer { |
| 29 | + |
| 30 | +template <typename Result, typename... Args> |
| 31 | +struct Cleanup { |
| 32 | + std::function<Result(Args...)> func; |
| 33 | +}; |
| 34 | + |
| 35 | +/// A simple stack data structure that manages a stack of std::function cleanups |
| 36 | +/// that can be invalidated by index. |
| 37 | +/// |
| 38 | +/// It is called asserting, since we force our user to explicitly pop the scope |
| 39 | +/// and abort otherwise. |
| 40 | +template <typename Result, typename... Args> |
| 41 | +class AssertingScope { |
| 42 | + using ScopeCleanup = Cleanup<Result, Args...>; |
| 43 | + SmallVector<Optional<ScopeCleanup>, 64> cleanups; |
| 44 | + bool didPop = false; |
| 45 | + |
| 46 | +protected: |
| 47 | + ~AssertingScope() { assert(didPop && "Did not pop scope?!"); } |
| 48 | + |
| 49 | + AssertingScope() {} |
| 50 | + |
| 51 | + /// Push a new SIL function based cleanup. Meant to be very |
| 52 | + /// lightweight. Returns the index of the cleanup. |
| 53 | + unsigned pushScope(std::function<Result(Args...)> func) { |
| 54 | + assert(!didPop && "Can not reuse scope once used?!"); |
| 55 | + unsigned index = cleanups.size(); |
| 56 | + cleanups.emplace_back(ScopeCleanup{func}); |
| 57 | + return index; |
| 58 | + } |
| 59 | + |
| 60 | + /// Invalidate the cleanup at the specific index. Asserts on index too big and |
| 61 | + /// on Optional has value. |
| 62 | + void invalidateCleanup(unsigned cleanupIndex) { |
| 63 | + assert(!didPop && "Should not invalidate once popped?!"); |
| 64 | + assert(cleanupIndex < cleanups.size()); |
| 65 | + assert(cleanups[cleanupIndex].hasValue()); |
| 66 | + cleanups[cleanupIndex] = None; |
| 67 | + } |
| 68 | + |
| 69 | + /// Pop the scope, running all non-Optional cleanups, and setting didPop. Once |
| 70 | + /// this is done the scope has been consumed and no longer has any state. |
| 71 | + /// |
| 72 | + /// Can only be done once the scope has been moved. |
| 73 | + void pop(Args... args) && { |
| 74 | + while (cleanups.size()) { |
| 75 | + auto val = cleanups.pop_back_val(); |
| 76 | + if (val) { |
| 77 | + val-> func(std::forward<Args>(args)...); |
| 78 | + } |
| 79 | + } |
| 80 | + didPop = true; |
| 81 | + } |
| 82 | + |
| 83 | + /// Can not be called once the scope is moved. |
| 84 | + void nonDestructivePop(Args... args) const { |
| 85 | + for (auto val : llvm::reverse(cleanups)) { |
| 86 | + if (val) { |
| 87 | + val-> func(std::forward<Args>(args)...); |
| 88 | + } |
| 89 | + } |
| 90 | + } |
| 91 | +}; |
| 92 | + |
| 93 | +class ScopedValue; |
| 94 | +class SILOptScope; |
| 95 | + |
| 96 | +/// Part of the SILRAIIScope interface that is known to ScopedValue. |
| 97 | +class SILOptScopeBase : public AssertingScope<void, SILInstruction *> { |
| 98 | +protected: |
| 99 | + SILOptScopeBase() {} |
| 100 | + |
| 101 | +public: |
| 102 | + using Index = unsigned; |
| 103 | + |
| 104 | + /// Destructive pop at end of scope. |
| 105 | + void popAtEndOfScope(SILInstruction *insertPt) && { |
| 106 | + std::move(*this).pop(insertPt); |
| 107 | + } |
| 108 | + |
| 109 | + /// Non-destructive pop along a control flow path that is serving as an early |
| 110 | + /// exit. |
| 111 | + void popAtEarlyExit(SILInstruction *insertPt) const { |
| 112 | + nonDestructivePop(insertPt); |
| 113 | + } |
| 114 | + |
| 115 | +private: |
| 116 | + friend class ScopedValue; |
| 117 | + |
| 118 | + /// Invalidate the passed in scoped value destructively. |
| 119 | + void invalidateValue(ScopedValue &&value); |
| 120 | +}; |
| 121 | + |
| 122 | +/// A light weight wrapper around a SILValue that also contains information |
| 123 | +/// about a Cleanup closure that ends the lifetime of the given value. |
| 124 | +/// |
| 125 | +/// In order to make it really easy to access the underlying value, we define |
| 126 | +/// operator * and operator-> as returning the underlying SILValue. It also |
| 127 | +/// defines explicit operator bool() so one should be able to use if statements |
| 128 | +/// to perform conditional initialization by returning an empty ScopedValue(). |
| 129 | +/// |
| 130 | +/// If one realizes that one does not actually need to cleanup a value, one can |
| 131 | +/// destructively forward the ScopedValue by writing: |
| 132 | +/// |
| 133 | +/// std::move(scopedValue).forward(); |
| 134 | +/// |
| 135 | +/// This will cause the cleanup in the SILOptScopeBase to be invalidated and |
| 136 | +/// thus will not be emitted when the scope is popped. |
| 137 | +class ScopedValue { |
| 138 | + friend class SILOptScopeBase; |
| 139 | + friend class SILOptScope; |
| 140 | + |
| 141 | + /// A back pointer to the scope we are managed by so that we can invalidate |
| 142 | + /// the cleanup associated with us. Also used to invalidate the underlying |
| 143 | + /// ScopedValue by setting this to nullptr. |
| 144 | + SILOptScopeBase *scope; |
| 145 | + |
| 146 | + /// The index in our parent scope object of our cleanup. This is used to |
| 147 | + /// enable invalidation. |
| 148 | + Optional<unsigned> scopeIndex; |
| 149 | + |
| 150 | + /// The underlying SILValue that we are working with. |
| 151 | + SILValue value; |
| 152 | + |
| 153 | + /// A scoped value that has a cleanup associated with it at the index \p |
| 154 | + /// scopeIndex within \p scope. |
| 155 | + ScopedValue(SILOptScopeBase &scope, SILValue value, unsigned scopeIndex) |
| 156 | + : scope(&scope), scopeIndex(scopeIndex), value(value) {} |
| 157 | + |
| 158 | + /// A scoped value that does not have an associated cleanup in the scope. |
| 159 | + ScopedValue(SILOptScopeBase &scope, SILValue value) |
| 160 | + : scope(&scope), scopeIndex(None), value(value) {} |
| 161 | + |
| 162 | +public: |
| 163 | + /// Default empty constructor. Should be used in combination with operator |
| 164 | + /// bool() to perform conditional initialization. |
| 165 | + ScopedValue() : scope(nullptr), scopeIndex(), value() {} |
| 166 | + |
| 167 | + /// Explicit operator that says if this is a valid scoped Value. |
| 168 | + /// |
| 169 | + /// Allows for conditional initialization via return value: |
| 170 | + /// |
| 171 | + /// if (auto value = getScopedValue(...)) { |
| 172 | + /// ... |
| 173 | + /// } |
| 174 | + explicit operator bool() const { return isValid(); } |
| 175 | + |
| 176 | + /// Check just for the validity of the value, this doesn't |
| 177 | + bool isValid() const { return scope && value; } |
| 178 | + |
| 179 | + /// Returns true if this scoped value has a cleanup associated with it that |
| 180 | + /// can be invalidated. |
| 181 | + /// |
| 182 | + /// Example: Result of SILOptScope::copyValue would return true, but result of |
| 183 | + /// a SILOptScope::borrowValue would return false since we do not allow for |
| 184 | + /// borrows to be cancelled. |
| 185 | + bool hasInvalidatableCleanup() const { |
| 186 | + assert(isValid()); |
| 187 | + return bool(scopeIndex); |
| 188 | + } |
| 189 | + |
| 190 | + /// Operator to access internal SILValue. |
| 191 | + SILValue operator*() const { |
| 192 | + assert(isValid()); |
| 193 | + return value; |
| 194 | + } |
| 195 | + |
| 196 | + /// Operator to call methods on internal SILValue. |
| 197 | + SILValue operator->() const { |
| 198 | + assert(isValid()); |
| 199 | + return value; |
| 200 | + } |
| 201 | + |
| 202 | + /// If this scope has a scoped index, invalidate the scoped value so that its |
| 203 | + /// cleanup is not emitted at end of scope. |
| 204 | + void invalidate() && { |
| 205 | + assert(isValid()); |
| 206 | + // If we have an invalidated cleanup, do the invalidation. |
| 207 | + if (hasInvalidatableCleanup()) { |
| 208 | + scope->invalidateValue(std::move(*this)); |
| 209 | + } |
| 210 | + // No matter what we do, make it so that if this object is used again, we |
| 211 | + // get an assert. |
| 212 | + scope = nullptr; |
| 213 | + scopeIndex.reset(); |
| 214 | + } |
| 215 | +}; |
| 216 | + |
| 217 | +inline void SILOptScopeBase::invalidateValue(ScopedValue &&value) { |
| 218 | + if (value.scopeIndex) |
| 219 | + invalidateCleanup(*value.scopeIndex); |
| 220 | +} |
| 221 | + |
| 222 | +/// A scope like stack data structure that one can use to manage cleanups for |
| 223 | +/// SILValues using light weight ScopedValue wrappers. This is done by using the |
| 224 | +/// copyValue/borrowValue methods. These copy/borrow the value and then push a |
| 225 | +/// destroy_value/end_borrow cleanup and return a ScopedValue containing that |
| 226 | +/// the user can then manipulate the value without needing to worry about the |
| 227 | +/// cleanup. If the user then decides a specific ScopedValue should be able to |
| 228 | +/// be cancelled, we allow for the ScopedValue to be invalidated |
| 229 | +class SILOptScope : public SILOptScopeBase { |
| 230 | +public: |
| 231 | + SILOptScope() {} |
| 232 | + |
| 233 | + /// Create a destroy_value cleanup for \p value. Returns a scoped value for \p |
| 234 | + /// value with a live cleanup. |
| 235 | + ScopedValue pushDestroyValue(SILValue value) { |
| 236 | + // We need to capture value by value, not by address. |
| 237 | + auto func = std::function<void(SILInstruction *)>( |
| 238 | + [innerValue = value](SILInstruction *insertPt) { |
| 239 | + SILBuilderWithScope builder(insertPt); |
| 240 | + builder.emitDestroyValue(RegularLocation::getAutoGeneratedLocation(), |
| 241 | + innerValue); |
| 242 | + }); |
| 243 | + return {*this, value, pushScope(func)}; |
| 244 | + } |
| 245 | + |
| 246 | + /// Copy \p value at \p insertPt and push a destroy_value cleanup. Return the |
| 247 | + /// new copied value as a ScopedValue with cleanup. |
| 248 | + ScopedValue copyValue(SILInstruction *insertPt, SILValue value) { |
| 249 | + SILValue copy = SILBuilderWithScope(insertPt).emitCopyValueOperation( |
| 250 | + insertPt->getLoc(), value); |
| 251 | + return pushDestroyValue(copy); |
| 252 | + } |
| 253 | + |
| 254 | + ScopedValue pushEndBorrow(SILValue value) { |
| 255 | + // We need to capture value by value, not by address. |
| 256 | + auto func = std::function<void(SILInstruction *)>( |
| 257 | + [innerValue = value](SILInstruction *insertPt) { |
| 258 | + SILBuilderWithScope builder(insertPt); |
| 259 | + builder.emitEndBorrowOperation( |
| 260 | + RegularLocation::getAutoGeneratedLocation(), innerValue); |
| 261 | + }); |
| 262 | + // We do not return the index of our end_borrow since an end_borrow should |
| 263 | + // never have its cleanup cancelled. |
| 264 | + pushScope(func); |
| 265 | + return {*this, value}; |
| 266 | + } |
| 267 | + |
| 268 | + /// Borrow \p value at \p insertPt and push an end_borrow cleanup. Return the |
| 269 | + /// new borrowed value as a ScopedValue without cleanup. The cleanup is not |
| 270 | + /// returned since end_borrows should not be cancellable. |
| 271 | + ScopedValue borrowValue(SILInstruction *insertPt, SILValue value) { |
| 272 | + if (!insertPt->getFunction()->hasOwnership() || |
| 273 | + value.getOwnershipKind().isCompatibleWith(OwnershipKind::Guaranteed)) |
| 274 | + return {}; |
| 275 | + SILValue borrow = SILBuilderWithScope(insertPt).emitBeginBorrowOperation( |
| 276 | + insertPt->getLoc(), value); |
| 277 | + return pushEndBorrow(borrow); |
| 278 | + } |
| 279 | +}; |
| 280 | + |
| 281 | +} // namespace siloptimizer |
| 282 | +} // namespace swift |
| 283 | + |
| 284 | +#endif |
0 commit comments