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py: Add note about -fno-crossjumping when compiling vm.c.

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Paul Sokolovsky 2014-12-28 07:44:09 +02:00 committed by Damien George
parent 96e22154d7
commit 23f1b5ff66
1 changed files with 8 additions and 0 deletions
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py/py.mk
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@ -162,3 +162,11 @@ $(PY_BUILD)/gc.o: CFLAGS += $(CSUPEROPT)
# optimising vm for speed, adds only a small amount to code size but makes a huge difference to speed (20% faster)
$(PY_BUILD)/vm.o: CFLAGS += $(CSUPEROPT)
# Optimizing vm.o for modern deeply pipelined CPUs with branch predictors
# may require disabling tail jump optimization. This will make sure that
# each opcode has its own dispatching jump which will improve branch
# branch predictor efficiency.
# http://article.gmane.org/gmane.comp.lang.lua.general/75426
# http://hg.python.org/cpython/file/b127046831e2/Python/ceval.c#l828
# http://www.emulators.com/docs/nx25_nostradamus.htm
#-fno-crossjumping