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enable live range shrinkage to relief register pressure

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docs:
I'd recommend to use this at
least for x86/x86-64.  I think any OOO processor with small or
moderate register file which does not use the 1st insn scheduling
might benefit from this too.

  On SPEC2000 for x86/x86-64 (I use Haswell processor, -O3 with
general tuning), the optimization usage results in smaller code size
in average (for floating point and integer benchmarks in 32- and
64-bit mode).  The improvement better visible for SPECFP2000 (although
I have the same improvement on x86-64 SPECInt2000 but it might be
attributed mostly mcf benchmark unstability).  It is about 0.5% for
32-bit and 64-bit mode.  It is understandable, as the optimization has
more opportunities to improve the code on longer BBs.  Different from
other heuristic optimizations, I don't see any significant worse
performance.  It gives practically the same or better performance (a
few benchmarks imporoved by 1% or more upto 3%).

  The single but significant drawback is additional compilation time
(4%-6%) as the 1st insn scheduling pass is quite expensive.

Source of docs: https://gcc.gnu.org/legacy-ml/gcc-patches/2013-11/msg00420.html
This commit is contained in:
RubenKelevra
2022-05-13 22:54:38 +02:00
parent ed3a8ad5d8
commit 44ac1fd5c8
1 changed files with 1 additions and 1 deletions
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2
utils.go
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@@ -727,7 +727,7 @@ func setupMakepkg(march string) error {
}
makepkgStr = strings.ReplaceAll(makepkgStr, " color ", " !color ")
// Add align-functions=32, see https://github.com/InBetweenNames/gentooLTO/issues/164 for more
makepkgStr = strings.ReplaceAll(makepkgStr, "-O2", "-O3 -falign-functions=32 -mpclmul -fdevirtualize-at-ltrans -fgcse-sm -fgcse-las")
makepkgStr = strings.ReplaceAll(makepkgStr, "-O2", "-O3 -falign-functions=32 -mpclmul -fdevirtualize-at-ltrans -fgcse-sm -fgcse-las -flive-range-shrinkage")
makepkgStr = strings.ReplaceAll(makepkgStr, "#MAKEFLAGS=\"-j2\"", "MAKEFLAGS=\"-j"+strconv.Itoa(conf.Build.Makej)+"\"")
makepkgStr = reMarch.ReplaceAllString(makepkgStr, "${1}"+march)
makepkgStr = strings.ReplaceAll(makepkgStr, "#PACKAGER=\"John Doe <john@doe.com>\"", "PACKAGER=\"ALHP "+march+" <alhp@harting.dev>\"")