gh-131798: JIT: optimize _LOAD_COMMON_CONSTANT

[trdthg]

Try to learn and make a small contribution :D

• Issue: Better uop coverage in the JIT optimizer #131798

[bedevere-app]

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[python-cla-bot]

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[Fidget-Spinner]

Thanks, this LGTM! Please remove the news entry, we don't need it as it's not a user facing code.

[bedevere-app]

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[Fidget-Spinner]

_LOAD_COMMON_CONSTANT x86_64 dissasembly in jit_stencils-x86_64-unknown-linux-gnu.h:

    // 0000000000000000 <_JIT_ENTRY>:
    // 0: 49 8b 47 10                   movq    0x10(%r15), %rax
    // 4: 48 b9 00 00 00 00 00 00 00 00 movabsq $0x0, %rcx
    // 0000000000000006:  R_X86_64_64  _JIT_OPARG
    // e: 0f b7 c9                      movzwl  %cx, %ecx
    // 11: 48 8b bc c8 60 68 03 00       movq    0x36860(%rax,%rcx,8), %rdi
    // 19: 8b 07                         movl    (%rdi), %eax
    // 1b: 85 c0                         testl   %eax, %eax
    // 1d: 78 06                         js      0x25 <_JIT_ENTRY+0x25>
    // 1f: ff c0                         incl    %eax
    // 21: 89 07                         movl    %eax, (%rdi)
    // 23: eb 04                         jmp     0x29 <_JIT_ENTRY+0x29>
    // 25: 48 83 cf 01                   orq     $0x1, %rdi

I think this is prior to our CFG optimizations in the backend, so it's not 100% accurate, but pretty close.

_LOAD_CONST_INLINE_BORROW:

    // 
    // _LOAD_CONST_INLINE_BORROW_r01.o:       file format elf64-x86-64
    // 
    // Disassembly of section .text:
    // 
    // 0000000000000000 <_JIT_ENTRY>:
    // 0: 48 bf 00 00 00 00 00 00 00 00 movabsq $0x0, %rdi
    // 0000000000000002:  R_X86_64_64  _JIT_OPERAND0
    // a: 48 83 cf 01                   orq     $0x1, %rdi

This is a really nice reduction. Good job!

[Fidget-Spinner]

We generally don't force push, because all PRs in CPython are squash-merged. So just push normal commits, thanks!

[Fidget-Spinner]

Once again, LGTM. Thanks for this!