Similarly to how we've always handled parameter types, we
now recursively expand tuples in result types and separately
determine a result convention for each result.
The most important code-generation change here is that
indirect results are now returned separately from each
other and from any direct results. It is generally far
better, when receiving an indirect result, to receive it
as an independent result; the caller is much more likely
to be able to directly receive the result in the address
they want to initialize, rather than having to receive it
in temporary memory and then copy parts of it into the
target.
The most important conceptual change here that clients and
producers of SIL must be aware of is the new distinction
between a SILFunctionType's *parameters* and its *argument
list*. The former is just the formal parameters, derived
purely from the parameter types of the original function;
indirect results are no longer in this list. The latter
includes the indirect result arguments; as always, all
the indirect results strictly precede the parameters.
Apply instructions and entry block arguments follow the
argument list, not the parameter list.
A relatively minor change is that there can now be multiple
direct results, each with its own result convention.
This is a minor change because I've chosen to leave
return instructions as taking a single operand and
apply instructions as producing a single result; when
the type describes multiple results, they are implicitly
bound up in a tuple. It might make sense to split these
up and allow e.g. return instructions to take a list
of operands; however, it's not clear what to do on the
caller side, and this would be a major change that can
be separated out from this already over-large patch.
Unsurprisingly, the most invasive changes here are in
SILGen; this requires substantial reworking of both call
emission and reabstraction. It also proved important
to switch several SILGen operations over to work with
RValue instead of ManagedValue, since otherwise they
would be forced to spuriously "implode" buffers.
Dead function elimination deletes functions making them zombies. A zombie is a
function whose name only exists because debug info might still refer to it.
However, later passes of specialization might create a new function by the same
name again. We now have a zombie function (which is just an alias to a deleted
method stub) and a function definition.
No test case since I could not reduce this to a small test case.
rdar://24659988
This is something that we have wanted for a long time and will enable us to
remove some hacks from the compiler (i.e. how we determine in the ARC optimizer
that we have "fatalError" like function) and also express new things like
"noarc".
Use malloc/free for allocating/freeing SIL instructions instead of using the BumpPtrAllocator. This allows for memory reuse and significantly reduces the memory footprint of the compiler.
For example, a peak memory usage during a compilation of the standard library and StdlibUnitTest is reduced by 25%-30%. The performance of the compiler seems to be not affected by this change, i.e. no slowdown is measured.
The use-after-free issues reported by build bots are fixed now.
rdar://23303031
The drivers for this change are providing a simpler API to SIL pass
authors, having a more efficient of the in-memory representation,
and ruling out an entire class of common bugs that usually result
in hard-to-debug backend crashes.
Summary
-------
SILInstruction
Old New
+---------------+ +------------------+ +-----------------+
|SILInstruction | |SILInstruction | |SILDebugLocation |
+---------------+ +------------------+ +-----------------+
| ... | | ... | | ... |
|SILLocation | |SILDebugLocation *| -> |SILLocation |
|SILDebugScope *| +------------------+ |SILDebugScope * |
+---------------+ +-----------------+
We’re introducing a new class SILDebugLocation which represents the
combination of a SILLocation and a SILDebugScope.
Instead of storing an inline SILLocation and a SILDebugScope pointer,
SILInstruction now only has one SILDebugLocation pointer. The APIs of
SILBuilder and SILDebugLocation guarantees that every SILInstruction
has a nonempty SILDebugScope.
Developer-visible changes include:
SILBuilder
----------
In the old design SILBuilder populated the InsertedInstrs list to
allow setting the debug scopes of all built instructions in bulk
at the very end (as the responsibility of the user). In the new design,
SILBuilder now carries a "current debug scope" state and immediately
sets the debug scope when an instruction is inserted.
This fixes a use-after-free issue with with SIL passes that delete
instructions before destroying the SILBuilder that created them.
Because of this, SILBuilderWithScopes no longer needs to be a template,
which simplifies its call sites.
SILInstruction
--------------
It is neither possible or necessary to manually call setDebugScope()
on a SILInstruction any more. The function still exists as a private
method, but is only used when splicing instructions from one function
to another.
Efficiency
----------
In addition to dropping 20 bytes from each SILInstruction,
SILDebugLocations are now allocated in the SILModule's bump pointer
allocator and are uniqued by SILBuilder. Unfortunately repeat compiles
of the standard library already vary by about 5% so I couldn’t yet
produce reliable numbers for how much this saves overall.
rdar://problem/22017421
This re-applies commit r31763 with a change to the predicate we
use for determining the linkage of a definition. It turns out we
could have definitions with a Clang body that were still public,
so instead of checking for a Clang body just check if the Clang
declaration is externally visible or not.
Swift SVN r31777
If an external SIL function has a Clang-generated body, I think this
means we have a static function, and we want to use Shared linkage,
not Public.
Add a new flag to SILFunction for this and plumb it through to
appease assertions from SILVerifier.
Swift SVN r31763
This patch implements the pre-specialization for the most popular generic types from the standard library. If there are invocations of generic functions from the standard library in the user-code and the compiler can find the specialized, optimized versions of these functions, then calls of generic functions are simply replaced by the calls of the specialized functions.
This feature is supposed to be used with -Onone to produce much faster (e.g. 5x-10x faster) executables in debug builds without impacting the compile time. In fact, the compile-time is even improved, because IRGen has less work to do. The feature can be considered a light-weight version of the -Odebug, because pre-specialization is limited in scope, but does not have a potentially negative compile-time impact compared to -Odebug. It is planned to enable it by default in the future.
This feature is disabled by default for the time being. It can be enabled by using a hidden flag: -Xllvm -use-prespecialized.
The implementation consists of two logical steps:
- When the standard library is being built, we force a creation of specializations for the most popular generic types from the stdlib, e.g. Arrays of integer and floating point types, Range<Int>, etc. The list of specializations is not fixed and can be easily altered by editing the Prespecialized.swift file, which is responsible for forcing the specialization of generic types (this is simple solution for now, until we have a proper annotation to indicate which specializations of a given generic type or function we want to generate by means of the pre-specialization). These specializations are then optimized and preserved in the stdlib dylib and in the Swift SIL module. The size increase of the stdlib due to creation of pre-specializations is currently about 3%-7%.
- When a user-code is being compiled with -Onone, the compiler would run a generic specializer over the user-code. If there are calls of generic functions from the standard library, the specializer would check if there is an existing specialization matching these invocations. If such a specialization is found, the original call is replaced by the call of this more efficient specialized version.
Swift SVN r30309
The two ways functions are created currently is via the two
SILModule::getOrCreateFunction(). One of the methods, takes in a raw mangled
name and uses that to create the function. The other takes in a SILDeclRef to
generate the mangled name. Most function emission (besides some thunk creation
functions) goes through the latter. For now we update the map there. This is ok,
since this map will only be used to provide extra verification that guaranteed
self is occuring everywhere that it is supposed to (since constructors and
destructors still have @owned self).
Swift SVN r27240
Previously some parts of the compiler referred to them as "fields",
and most referred to them as "elements". Use the more generic 'elements'
nomenclature because that's what we refer to other things in the compiler
(e.g. the elements of a bracestmt).
At the same time, make the API better by providing "getElement" consistently
and using it, instead of getElements()[i].
NFC.
Swift SVN r26894
This can only happen in the closure specializer and the generic
specializer since all other specializations either copy the linkage of
the original function (function signature opts) or clone closures/thunks
which have shared linkage.
I put in a verifier check that makes sure we do not create shared
versions of these functions. The real problem has to do with serializing
these sorts of functions, but since we always serialize shared
functions, it makes sense to just ban it.
rdar://20082696
Swift SVN r26001
This is also useful in general SIL passes when generating thunks. I am going to
use this in function signature optimization and closure specialization.
Swift SVN r25356
This will have an effect on inlining into thunks.
Currently this flag is set for witness thunks and thunks from function signature optimization.
No change in code generation, yet.
Swift SVN r24998
The underlying problem is that e.g. even if a method is private but its class is public, the method can be referenced from another module - from the vtable of a derived class.
So far we handled this by setting the SILLinkage of such methods according to the visibility of the class. But this prevented dead method elimination.
Now I set the SILLinkage according to the visibility of the method. This enables dead method elimination, but it requires the following:
1) Still set the linkage in llvm so that it can be referenced from outside.
2) If the method is dead and eliminated, create a stub for it (which calls swift_reportMissingMethod).
Swift SVN r23889
This prevented dead function removal of inlined dead functions. Beside the stdlib it's mostly
an issue of SIL size (and therefore compiletime), because llvm did remove such functions anyway.
Swift SVN r22301
Now the SILLinkage for functions and global variables is according to the swift visibility (private, internal or public).
In addition, the fact whether a function or global variable is considered as fragile, is kept in a separate flag at SIL level.
Previously the linkage was used for this (e.g. no inlining of less visible functions to more visible functions). But it had no effect,
because everything was public anyway.
For now this isFragile-flag is set for public transparent functions and for everything if a module is compiled with -sil-serialize-all,
i.e. for the stdlib.
For details see <rdar://problem/18201785> Set SILLinkage correctly and better handling of fragile functions.
The benefits of this change are:
*) Enable to eliminate unused private and internal functions
*) It should be possible now to use private in the stdlib
*) The symbol linkage is as one would expect (previously almost all symbols were public).
More details:
Specializations from fragile functions (e.g. from the stdlib) now get linkonce_odr,default
linkage instead of linkonce_odr,hidden, i.e. they have public visibility.
The reason is: if such a function is called from another fragile function (in the same module),
then it has to be visible from a third module, in case the fragile caller is inlined but not
the specialized function.
I had to update lots of test files, because many CHECK-LABEL lines include the linkage, which has changed.
The -sil-serialize-all option is now handled at SILGen and not at the Serializer.
This means that test files in sil format which are compiled with -sil-serialize-all
must have the [fragile] attribute set for all functions and globals.
The -disable-access-control option doesn't help anymore if the accessed module is not compiled
with -sil-serialize-all, because the linker will complain about unresolved symbols.
A final note: I tried to consider all the implications of this change, but it's not a low-risk change.
If you have any comments, please let me know.
Swift SVN r22215
This will let the performance inliner inline a function even if the costs are too high.
This attribute is only a hint to the inliner.
If the inliner has other good reasons not to inline a function,
it will ignore this attribute. For example if it is a recursive function (which is
currently not supported by the inliner).
Note that setting the inline threshold to 0 does disable performance inlining at all and in
this case also the @inline(__always) has no effect.
Swift SVN r21452
This disables inlining at the SIL level. LLVM inlining is still enabled. We can
use this to expose one function at the SIL level - which can participate in
dominance based optimizations but which is implemented in terms of a cheap check
and an expensive check (function call) that benefits from LLVM's inlining.
Example:
The inline(late) in the example below prevents inlining of the two checks. We
can now perform dominance based optimizations on isClassOrObjExistential.
Without blocking inlining the optimizations would apply to the sizeof check
only and we would have multiple expensive function calls.
@inline(late)
func isClassOrObjExistential(t: Type) -> Bool{
return sizeof(t) == sizeof(AnyObject) &&
swift_isClassOrObjExistential(t)
}
We do want inlining of this function to happen at the LLVM level because the
first check is constant folded away - IRGen replaces sizeof by constants.
rdar://17961249
Swift SVN r21286
AST context substitution may produce a metatype, function type, or other type that requires lowering. Handle this special case to fix a crash when emitting protocol conformances with metatypes or functions as associated types. <rdar://problem/17501507>
Swift SVN r19580
