The old invalidation lattice was incorrect because changes to control flow could cause changes to the
call graph, so we've decided to change the way passes invalidate analysis. In the new scheme, the lattice
is replaced with a list of traits that passes preserve or invalidate. The current traits are Calls and Branches.
Now, passes report which traits they preserve, which is the opposite of the previous implementation where
passes needed to report what they invalidate.
Node: I tried to limit the changes in this commit to mechanical changes to ease the review. I will cleanup some
of the code in a following commit.
Swift SVN r26449
This is off by default and is a modified version of r21996 (reverted in r22001).
Update SILGlobalOpt to remove "once" call from addressor and set the
InitializerF for SILGlboalVariable if legal.
For calls to addressor in non-cold block, we check the addressor to find out
the globalinit_func and the associated SILGlobalVariable. If legal, we set
InitializerF of SILGlobalVariable and remove "once" call from addressor.
The current rules for legality:
1> the addressor contains a single "once" call and it calls globalinit_func.
2> the globalinit_func is called by "once" from a single location.
When we inline the addressor, the globalinit_func will be called by "once"
from multiple locations. After we remove the "once" from the addressor, the
inlined version will mistakely initialize the global variable again.
3> the globalinit_func is trivial as defined by
SILGlobalVariable::canBeStaticInitializer().
Update IRGen to generate constant initializers for global variables with static
initializers (i.e non-null InitializerF).
Joe's suggestion on having the static initializer to return the result instead
of storing it is not implemented in this commit. But we do verify that a static
initializer has a single store to the global variable. The suggestion is tracked
in rdar://18382039.
Implement rdar://16621368, rdar://18169093.
Swift SVN r22083
r21996 tries to take advantage of LLVM global opt that eliminates global
initializers by using llvm.global_ctors. Revert it because we can't guarantee
that they will be optimized to constant initializers.
A modifed version will follow that uses constant initializers directly in IRGen.
Swift SVN r22001
Update SILGlobalOpt to remove "once" call from addressor and set the
InitializerF for SILGlboalVariable if legal.
For calls to addressor in non-cold block, we check the addressor to find out
the globalinit_func and the associated SILGlobalVariable. If legal, we set
InitializerF of SILGlobalVariable and remove "once" call from addressor.
The current rules for legality:
1> the addressor contains a single "once" call
2> it calls globalinit_func
3> the globalinit_func is called by "once" from a single location
4> the globalinit_func is trivial
Update IRGen to emit llvm.global_ctors for global variables with static
initializers (i.e non-null InitializerF).
Performance --------
After:
Totals,54,67202,67202,67202,0,0 Onone
Totals,54,88948,88948,88948,0,0 O
Totals,54,71222,71222,71222,0,0 Ounchecked
Totals,54,66405,66405,66405,0,0 Onone
Totals,54,88759,88759,88759,0,0 O
Totals,54,71761,71761,71761,0,0 Ounchecked
Before:
Totals,55,68133,68133,68133,0,0 Onone
Totals,55,92458,92458,92458,0,0 O
Totals,55,72262,72262,72262,0,0 Ounchecked
Totals,55,69022,69022,69022,0,0 Onone
Totals,55,92178,92178,92178,0,0 O
Totals,55,72593,72593,72593,0,0 Ounchecked
Swift SVN r21996
<rdar://problem/16792521> Hoist globals initializers out of loops.
Long term, we should recognize hot/cold idioms for ObjC support and
provide an analysis that identifies cold branch targets. However,
identifying loops is trivial and self-contained so more appropriate
for WWDC.
I have not been able to reproduce the StringSort regression. However,
I compared Benchmark.swift with Release build before and after
enabling the pass with this patch and saw no regressions.
Swift SVN r17554
Currently, this pass simply hoists calls to addressor functions up to
the function entry point. This solves most of the perfomance problem.
Fixes <rdar://problem/16500879> Need to hoist @swift_once outside of loops.
Swift SVN r16684