Statically initialized objects #11537
Conversation
|
@swift-ci Please test |
|
Build failed |
|
Build failed |
docs/SIL.rst
Outdated
|
|
||
| A global can have a static initializer if it's initial value can be |
| the global variable is a statically initialized object. In this case the | ||
| variable cannot be used as l-value, i.e. the reference to the object cannot be | ||
| modified. As a consequence the variable cannot be accessed with ``global_addr`` | ||
| but only with ``global_value``. |
There was a problem hiding this comment.
Can we model this more generally, by having a sil_global track whether it's immutable or not, and only allowing object literals and global_value accesses on immutable sil_globals?
There was a problem hiding this comment.
I'll leave this open for a follow-up work. I think this needs some more discussion.
There was a problem hiding this comment.
Fair enough. Another thing that crossed my mind—is the constraint on object strictly necessary? It seems like something we could support generally by lowering to alloc_ref + initialization of the class fields during IRGen, and it might make some analyses easier to be able to represent object instantiations that way.
eeckstein
force-pushed
the
static-initializers
branch
from
217411f
to
49fd192
Compare
|
@swift-ci test and merge |
1 similar comment
|
@swift-ci test and merge |
eeckstein
force-pushed
the
static-initializers
branch
from
a6cbdb3
to
49ab322
Compare
|
@swift-ci smoke test and merge |
1 similar comment
|
@swift-ci smoke test and merge |
…without a function context just refactoring, NFC
Plus a small refactoring to simplify the code: remove the inner SILPrintFunctionContext struct
Don't pass the basic block to parseSILInstruction. NFC
Static initializers are now represented by a list of literal and aggregate instructions in a SILGlobalVariable. For details see SIL.rst. This representation is cleaner than what we did so far (point to the initializer function and do some pattern matching). One implication of that change is that now (a subset of) instructions not necessarily have a parent function. Regarding the generated code it's a NFC. Also the swift module format didn't change because so far we don't serializer global variables.
…lly allocated object
…ail allocated elements
…tatically initialized objects. This commit contains: -) adding the new instructions + infrastructure, like parsing, printing, etc. -) support in IRGen to generate global object-variables (i.e. "heap" objects) which are statically initialized in the data section. -) IRGen for global_value which lazily initializes the object header and returns a reference to the object. For details see the documentation of the new instructions in SIL.rst.
Mainly this is done for array literals. This new optimization creates a statically initialized global variable which is the allocated object. The alloc_ref instruction is replaced by a global_value instruction. This optimization can give significant performance improvements for large array literals.
eeckstein
force-pushed
the
static-initializers
branch
from
49ab322
to
375526a
Compare
|
@swift-ci smoke test and merge |
1 similar comment
|
@swift-ci smoke test and merge |
|
https://ci.swift.org/job/oss-swift-package-osx/89/ |
|
|
||
| Returns the value of a global variable which has been previously initialized | ||
| by ``alloc_global``. It is undefined behavior to perform this operation on a | ||
| global variable which has not been initialized, except the global variable |
There was a problem hiding this comment.
Missing "if": "except if the global variable"
Outline heap objects to global variables.
Mainly this is done for array literals.
This new optimization creates a statically initialized global variable which is the allocated object.
The alloc_ref instruction is replaced by a global_value instruction.
This optimization gives significant performance improvements for large array literals (e.g. for the ArrayLiteral benchmark).