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b9ef5708e2
VarargExpansionExpr shows up in call argument lists in synthesized initializers and modify accessors when we need to forward arguments to a call taking varargs. Previously we would say that the type of VarargExpansionExpr is $T when its subexpression type is [$T]. matchCallArguments() would then 'collect' the single VarargExpansionExpr into a variadic argument list with a single element, and build an ArgumentShuffleExpr for the argument list. In turn, SILGen would peephole vararg emission of a variadic argument list with a single entry that happens to be a VarargExpansionExpr, by returning the subexpression's value, which happened to be an array of the right element type, instead of building a new array containing the elements of the variadic argument list. This was all too complicated. Instead, let's say that the type of a VarargExpansionExpr is [$T], except that when it appears in a TupleExpr, the variadic bit of the corresponding element is set. Then, matchCallArguments() needs to support a case where both the parameter and argument list have a matching vararg element. In this case, instead of collecting multiple arguments into a single variadic argument list, we treat the variadic argument like an ordinary parameter, bypassing construction of the ArgumentShuffleExpr altogether. Finally, SILGen now needs to be able to emit a VarargExpansionExpr in ordinary rvalue position, since it now appears as a child of a TupleExpr; it can do this by simply emitting the sub-expression to produce an array value.
77 lines
2.4 KiB
C++
77 lines
2.4 KiB
C++
//===--- Varargs.h - SIL generation for (native) Swift varargs --*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// A storage structure for holding a destructured rvalue with an optional
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// cleanup(s).
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// Ownership of the rvalue can be "forwarded" to disable the associated
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// cleanup(s).
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_LOWERING_VARARGS_H
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#define SWIFT_LOWERING_VARARGS_H
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#include "ManagedValue.h"
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#include "swift/SIL/AbstractionPattern.h"
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namespace swift {
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namespace Lowering {
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class SILGenFunction;
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class TypeLowering;
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/// Information about a varargs emission.
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class VarargsInfo {
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ManagedValue Array;
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CleanupHandle AbortCleanup;
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SILValue BaseAddress;
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AbstractionPattern BasePattern;
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const TypeLowering &BaseTL;
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public:
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VarargsInfo(ManagedValue array, CleanupHandle abortCleanup,
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SILValue baseAddress, const TypeLowering &baseTL,
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AbstractionPattern basePattern)
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: Array(array), AbortCleanup(abortCleanup),
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BaseAddress(baseAddress), BasePattern(basePattern), BaseTL(baseTL) {}
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/// Return the array value. emitEndVarargs() is really the only
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/// function that should be accessing this directly.
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ManagedValue getArray() const {
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return Array;
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}
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CleanupHandle getAbortCleanup() const { return AbortCleanup; }
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/// An address of the lowered type.
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SILValue getBaseAddress() const { return BaseAddress; }
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AbstractionPattern getBaseAbstractionPattern() const {
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return BasePattern;
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}
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const TypeLowering &getBaseTypeLowering() const {
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return BaseTL;
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}
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};
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/// Begin a varargs emission sequence.
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VarargsInfo emitBeginVarargs(SILGenFunction &SGF, SILLocation loc,
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CanType baseTy, CanType arrayTy,
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unsigned numElements);
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/// Successfully end a varargs emission sequence.
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ManagedValue emitEndVarargs(SILGenFunction &SGF, SILLocation loc,
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VarargsInfo &&varargs);
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} // end namespace Lowering
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} // end namespace swift
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#endif
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