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Improve performance for switch in ceval.c when using MSVC #91719

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gvanrossum opened this issue Apr 20, 2022 · 1 comment
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Improve performance for switch in ceval.c when using MSVC #91719

gvanrossum opened this issue Apr 20, 2022 · 1 comment
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performance type-bug

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@gvanrossum
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@gvanrossum gvanrossum commented Apr 20, 2022

We've received reports of MSVC not generating optimal code, e.g. gh-89279.

One possible improvement would be to get the big switch statement in ceval.c to generate better code. It's been rumored that MSVC will generate essentially a computed goto if all cases are filled.

See my investigations at faster-cpython/ideas#321 (comment)
@gvanrossum gvanrossum added the type-bug label Apr 20, 2022
@AlexWaygood AlexWaygood added the performance label Apr 20, 2022
gvanrossum added a commit that referenced this issue Apr 21, 2022
@gvanrossum
GH-91719: Make MSVC generate somewhat faster switch code (#91718)
f8dc618 
Apparently a switch on an 8-bit quantity where all cases are
present generates a more efficient jump (doing only one indexed
memory load instead of two).

So we make opcode and use_tracing uint8_t, and generate a macro
full of extra `case NNN:` lines for all unused opcodes.

See faster-cpython/ideas#321 (comment)
@gvanrossum
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@gvanrossum gvanrossum commented Apr 23, 2022

Fixed by #91718.

@gvanrossum gvanrossum closed this Apr 23, 2022
@gvanrossum gvanrossum mentioned this issue Apr 23, 2022
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vstinner added a commit to vstinner/cpython that referenced this issue Apr 25, 2022
@vstinner
pythongh-91719: Add pycore_opcode.h internal header file
29ac5b2 
Move internal C API from Include/opcode.h to a new
Include/internal/pycore_opcode.h file. Move:

* EXTRA_CASES
* _PyOpcode_Caches
* _PyOpcode_Deopt
* _PyOpcode_Jump
* _PyOpcode_OpName
* _PyOpcode_RelativeJump
vstinner added a commit to vstinner/cpython that referenced this issue Apr 25, 2022
@vstinner
pythongh-91719: Add pycore_opcode.h internal header file
d0af188 
Move the following API from Include/opcode.h (public C API) to a new
Include/internal/pycore_opcode.h header file (internal C API):

* EXTRA_CASES
* _PyOpcode_Caches
* _PyOpcode_Deopt
* _PyOpcode_Jump
* _PyOpcode_OpName
* _PyOpcode_RelativeJump
vstinner added a commit that referenced this issue Apr 25, 2022
@vstinner
gh-91719: Add pycore_opcode.h internal header file (#91906)
64a54e5 
Move the following API from Include/opcode.h (public C API) to a new
Include/internal/pycore_opcode.h header file (internal C API):

* EXTRA_CASES
* _PyOpcode_Caches
* _PyOpcode_Deopt
* _PyOpcode_Jump
* _PyOpcode_OpName
* _PyOpcode_RelativeJump
vstinner pushed a commit that referenced this issue Apr 27, 2022
@sweeneyde
gh-91719: Mark pycore_opcode.h as generated in .gitattributes (#91976)
b733708
@gvanrossum gvanrossum mentioned this issue Apr 28, 2022
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