[sil] Add a move_value instruction. #39267
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This is a new instruction that can be used by SILGen to perform a semantic move in between two entities that are considered separate variables at the AST level. I am going to use it to implement an experimental borrow checker. This PR contains the following: 1. I define move_value, setup parsing, printing, serializing, deserializing, cloning, and filled in all of the visitors as appropriate. 2. I added createMoveValue and emitMoveValueOperation SILBuilder APIs. createMoveValue always creates a move and asserts is passed a trivial type. emitMoveValueOperation in contrast, will short circuit if passed a trivial value and just return the trivial value. 3. I added IRGen tests to show that we can push this through the entire system. This is all just scaffolding for the instruction to live in SIL land and as of this PR doesn't actually do anything.
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@swift-ci smoke test |
| %1 = move_value %0 : $@_moveOnly A | ||
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| Performs a move of the operand, ending its lifetime. When ownership is enabled, | ||
| it always takes in an `@owned T` and produces a new `@owned @_moveOnly T`. |
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@gottesmm Both the operand and result of move_value may be either moveOnly or copyable.
Whether either value is moveOnly depends on its type. The important thing about this operation is that it can do a type conversion in either direction between 'moveOnly T' and 'T'. It can also simply perform a move without doing any type conversion.
For the purpose of SIL ownership, it simply forwards an owned value. It has no special properties.
| @@ -249,6 +249,9 @@ OPERAND_OWNERSHIP(DestroyingConsume, EndLifetime) | |||
| OPERAND_OWNERSHIP(DestroyingConsume, BeginCOWMutation) | |||
| OPERAND_OWNERSHIP(DestroyingConsume, EndCOWMutation) | |||
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| // TODO: Should this be a forwarding consume. | |||
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Yes, it should be ForwardingConsume, so why isn't it!
| require(mvi->getOperand()->getType().isObject(), | ||
| "Operand value should be an object"); | ||
| require(mvi->getType() == mvi->getOperand()->getType(), | ||
| "Result and operand must have the same type, today."); |
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Clearly this type restriction needs to be relaxed once you have moveOnly SIL types
| // CHECK-NEXT: } // end sil function 'test_movevalue_parsing' | ||
| sil [ossa] @test_movevalue_parsing : $@convention(thin) (@owned Builtin.NativeObject) -> @owned Builtin.NativeObject { | ||
| bb0(%0 : @owned $Builtin.NativeObject): | ||
| %1 = move_value %0 : $Builtin.NativeObject |
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Note: %1 should be copyable since there's no moveOnly on its SIL type.
This is a new instruction that can be used by SILGen to perform a semantic move
in between two entities that are considered separate variables at the AST
level. I am going to use it to implement an experimental borrow checker.
This PR contains the following:
cloning, and filled in all of the visitors as appropriate.
APIs. createMoveValue always creates a move and asserts is passed a trivial
type. emitMoveValueOperation in contrast, will short circuit if passed a
trivial value and just return the trivial value.
This is all just scaffolding for the instruction to live in SIL land and as of
this PR doesn't actually do anything.