Verify that
* the destination address is an alloc_stack
* the stack location is not modified beside a store_borrow
* the stack location has been initialized when used
Unless the type is a trivial scalar. As a follow-up we could try to
prove that the referenced object is unique, but that seems more
natural for DeadObjectElimination.
This optimization was never correct because references may alias. See
rdar://36038096 ([SR-6608] DeadCodeElimination removes fix_lifetime
instructions.)
Fixes rdar://74759728 (The compiler/optimizer seems to be shortening
the lifetime too early)
Enable most simplify-cfg optimizations as long as the block arguments
have trivial types. Enable most simplify CFG unit tests cases.
This massively reduces the size of the CFG during OSSA passes.
Test cases that aren't supported in OSSA yet have been moved to a
separate test file for disabled OSSA tests,
Full simplify-cfg support is currently blocked on OSSA utilities which
I haven't checked in yet.
This is kind of complicated, because an enum can be trivial for one case and not trivial for another case. We need to check at which parts of the function we can prove that the enum does (or could) have a trivial case. In such a branch, it's not required in SIL to destroy the enum location.
Also, document the rules and requirements for enum memory locations in SIL.rst.
rdar://73770085
In the common case, we cannot have redundant @owned and @guaranteed phi
args. However, if the incoming values had none ownership and were passed
as an @owned or an @guaranteed phi arg, they can be considered as redundant.
For such redundant @owned phi args, create a copy value, and use the
copy to replace all uses of the redundant phi arg.
For such redundant @guaranteed phi args, we turn off the optimization
currently. We cannot just create a borrow scope and use the new borrowed
value for replacement. We will also have to re-write the consuming uses of
the @guaranteed values such that the newly created borrow scope is
within the scope of its operand.
If we know that we have a FunctionRefInst (and not another variant of FunctionRefBaseInst), we know that getting the referenced function will not be null (in contrast to FunctionRefBaseInst::getReferencedFunctionOrNull).
NFC
This PR simplifies the handling of store [assign] in Mem2Reg by always
converting it to a store [init].
Also fixes an edge case where store [assign] in a non entry block was
not the first store of an alloc_stack with uses in multiple blocks.
This is needed for non-OSSA SIL: in case we see a destroyArray builtin, we can safely remove the otherwise dead array.
This optimization kicks in later in the pipeline, after array semantics are already inlined (for early SIL, DeadObjectElimination can remove arrays based on semantics).
rdar://73569282
https://bugs.swift.org/browse/SR-14100
A reborrow's base value may change if the base value is also passed as
an operand on a branch. Record reborrow dependencies so that we can mark
the base value as live, if the reborrow was also live. This ensures we
do not insert destroy_value on the base value prematurely before the
lifetime of the reborrow ends.
Instead make `findJointPostDominatingSet` a stand-alone function.
There is no need to keep the temporary SmallVector alive across multiple calls of findJointPostDominatingSet for the purpose of re-using malloc'ed memory. The worklist usually contains way less elements than its small size.
My goal was to reduce the size of SILLocation. It now contains only of a storage union, which is basically a pointer and a bitfield containing the Kind, StorageKind and flags. By far, most locations are only single pointers to an AST node. For the few cases where more data needs to be stored, this data is allocated separately: with the SILModule's bump pointer allocator.
While working on this, I couldn't resist to do a major refactoring to simplify the code:
* removed unused stuff
* The term "DebugLoc" was used for 3 completely different things:
- for `struct SILLocation::DebugLoc` -> renamed it to `FilePosition`
- for `hasDebugLoc()`/`getDebugSourceLoc()` -> renamed it to `hasASTNodeForDebugging()`/`getSourceLocForDebugging()`
- for `class SILDebugLocation` -> kept it as it is (though, `SILScopedLocation` would be a better name, IMO)
* made SILLocation more "functional", i.e. replaced some setters with corresponding constructors
* replaced the hand-written bitfield `KindData` with C bitfields
* updated and improved comments
