Description

markshannon

opened on Jun 12, 2023

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As we move towards generating more components from the instruction definition file (bytecodes.c), it helps if the instructions have regular formats and stack effects.
Currently the stack effects can be simple, variable, conditional or complex.

• Simple: Does not depend on the operand (oparg)
• Variable: Either pops or pushes oparg * k items.
• Conditional: Pushes a value conditional on oparg & 1
• Complex: The stack effect depends on a set of flags embedded in oparg.

We can easily get rid of the complex case. There are only two cases, MAKE_FUNCTION and FORMAT_VALUE. Both can easily broken down into simple (and faster) parts.

We might want to get rid of condition stack effects, as it would simplify things, but performance may suffer as both LOAD_GLOBAL and LOAD_ATTR are conditional and they are performance critical.

Linked PRs

• GH-105678: Split MAKE_FUNCTION into MAKE_FUNCTION and SET_FUNCTION_ATTRIBUTE #105680
• gh-105678: document SET_FUNCTION_ATTRIBUTE #105843

Activity

1. markshannon

   added

   performancePerformance or resource usagePerformance or resource usage

   on Jun 12, 2023
2. markshannon

   changed the title [-]Remove irregular opargs[/-] [+]Remove irregular stack effects[/+] on Jun 12, 2023
3. markshannon

   added a commit that references this issue on Jun 13, 2023

   GH-105678: Split MAKE_FUNCTION into MAKE_FUNCTION and SET_FUNCTION_AT…

   09ffa69
4. carljm

   added 2 commits that reference this issue on Jun 16, 2023

   pythongh-105678: document SET_FUNCTION_ATTRIBUTE

   518e991

   gh-105678: document SET_FUNCTION_ATTRIBUTE (#105843)

   b356a47
5. gvanrossum

   added a commit that references this issue on Jun 18, 2023

   pythongh-105678: document SET_FUNCTION_ATTRIBUTE (python#105843)

   ca53b70
6. gvanrossum commented on Jun 18, 2023

   

   gvanrossum

   on Jun 18, 2023

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   @markshannon Can this be closed yet? I doubt that we'll be removing conditional stack effects (at least conditional pushes). Note that we now support conditional pushes in the final op of a macro. (If needed the same approach could be used to support conditional pops in the first op.)
7. markshannon commented on Jun 19, 2023

   

   markshannon

   on Jun 19, 2023

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   Yes, this can be closed.
   We might want to remove conditional stack effects in the future, but not now.
8. markshannon

   closed this as completedon Jun 19, 2023

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