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bpo-40302: Optimize UTF-32 encoder SWAB4() #19572

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Merged
merged 1 commit into from
Apr 17, 2020
Merged

bpo-40302: Optimize UTF-32 encoder SWAB4() #19572

merged 1 commit into from
Apr 17, 2020

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vstinner
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@vstinner vstinner commented Apr 17, 2020

Use a | b instead of a + b in UCS-2 implementation of SWAB4().

https://bugs.python.org/issue40302

Use a | b instead of a + b in  UCS-2 implementation of SWAB4().
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pitrou commented Apr 17, 2020

Does this optimize anything? Browsing through https://www.agner.org/optimize/instruction_tables.pdf, it seems ADD r,r generally has 1 cycle latency, exactly like OR r,r (where r is an arbitrary register).

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Does this optimize anything? Browsing through https://www.agner.org/optimize/instruction_tables.pdf, it seems ADD r,r generally has 1 cycle latency, exactly like OR r,r (where r is an arbitrary register).

Sorry, the commit title is maybe wrong. It's more about consistency with other macros with all use a|b rather than a+b.

@vstinner vstinner merged commit d7c657d into python:master Apr 17, 2020
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I removed "optimize" from the merged commit message ;-)

@vstinner vstinner deleted the SWAB4 branch April 17, 2020 17:13
CuriousLearner added a commit to CuriousLearner/cpython that referenced this pull request May 29, 2020
* master: (1985 commits)
  bpo-40179: Fix translation of #elif in Argument Clinic (pythonGH-19364)
  bpo-35967: Skip test with `uname -p` on Android (pythonGH-19577)
  bpo-40257: Improve help for the typing module (pythonGH-19546)
  Fix two typos in multiprocessing (pythonGH-19571)
  bpo-40286: Use random.randbytes() in tests (pythonGH-19575)
  bpo-40286: Makes simpler the relation between randbytes() and getrandbits() (pythonGH-19574)
  bpo-39894: Route calls from pathlib.Path.samefile() to os.stat() via the path accessor (pythonGH-18836)
  bpo-39897: Remove needless `Path(self.parent)` call, which makes `is_mount()` misbehave in `Path` subclasses. (pythonGH-18839)
  bpo-40282: Allow random.getrandbits(0) (pythonGH-19539)
  bpo-40302: UTF-32 encoder SWAB4() macro use a|b rather than a+b (pythonGH-19572)
  bpo-40302: Replace PY_INT64_T with int64_t (pythonGH-19573)
  bpo-40286: Add randbytes() method to random.Random (pythonGH-19527)
  bpo-39901: Move `pathlib.Path.owner()` and `group()` implementations into the path accessor. (pythonGH-18844)
  bpo-40300: Allow empty logging.Formatter.default_msec_format. (pythonGH-19551)
  bpo-40302: Add pycore_byteswap.h header file (pythonGH-19552)
  bpo-40287: Fix SpooledTemporaryFile.seek() return value (pythonGH-19540)
  Minor modernization and readability improvement to the tokenizer example (pythonGH-19558)
  bpo-40294: Fix _asyncio when module is loaded/unloaded multiple times (pythonGH-19542)
  Fix parameter names in assertIn() docs (pythonGH-18829)
  bpo-39793: use the same domain on make_msgid tests (python#18698)
  ...
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