Reland 877a9f9abec61f06e39f1cd872e37b828139c2d1 since D138654 (parent)
has been fixed with 9ebaf4fef4aac89d4eff08e48185d61bc893f14e and with
8f1e11c5a7d70f96943a72649daa69f152d73e90.
Differential Revision: https://reviews.llvm.org/D126455
This reverts commit 877a9f9abec61f06e39f1cd872e37b828139c2d1.
It depends on the parent revision 42c2dc401742266da3e0251b6c1ca491f4779963
which needs to be reverted as it broke some buildbots, so reverting both.
The aim of this patch is to minimize the compilation time overhead of
running Function Specialization. It is about 40% slower to run as a
standalone pass (IPSCCP + FuncSpec vs IPSCCP with FuncSpec) according
to my measurements. I compiled the llvm testsuite with NewPM-O3 + LTO
and measured single threaded [user + system] time of IPSCCP and FuncSpec
by passing the '-time-passes' option to lld. Then I compared the two
configurations in terms of Instruction Count of the total compilation
(not of the individual passes) as in https://llvm-compile-time-tracker.com.
Geomean for non-LTO builds is -0.25% and LTO is -0.5% approximately.
You can find more info below:
https://discourse.llvm.org/t/rfc-should-we-enable-function-specialization/61518
Differential Revision: https://reviews.llvm.org/D126455
When calculating the specialization bonus for a given function argument,
we recursively traverse the chain of (certain) users, accumulating the
instruction costs. Then we exponentially increase the bonus to account
for loop nests. This is problematic for two reasons: (a) the users might
not themselves be inside the loop nest, (b) if they are we are accounting
for it multiple times. Instead we should be adjusting the bonus before
traversing the user chain.
This reduces the instruction count for CTMark (newPM-O3) when Function
Specialization is enabled without actually reducing the amount of
specializations performed (geomean: -0.001% non-LTO, -0.406% LTO).
Differential Revision: https://reviews.llvm.org/D136692
It would waste time to specialize a function which would inline finally.
This patch did two things:
- Don't specialize functions which are always-inline.
- Don't spescialize functions whose lines of code are less than threshold
(100 by default).
For spec2017int, this patch could reduce the number of specialized
functions by 33%. Then the compile time didn't increase for every
benchmark.
Reviewed By: SjoerdMeijer, xbolva00, snehasish
Differential Revision: https://reviews.llvm.org/D107897
The original implementation calculating UserBonus uses operator ^, which means XOR in C++
language.
At the first glance of reviewing, I thought it should be power, my bad.
It doesn't make sense to use XOR here. So I believe it should be a
carelessness as I made.
Test Plan: check-all
Reviewed By: SjoerdMeijer
Differential Revision: https://reviews.llvm.org/D104282
