[all-commits] [llvm/llvm-project] 7190fa: [WIP][AMDGPU] Improve the handling of `inreg` argu...

[Shilei Tian via All-commits]

  Branch: refs/heads/users/shiltian/inreg-vgpr-improvement
  Home:   https://github.com/llvm/llvm-project
  Commit: 7190fa6b16442e24a46a61357fc02f2e268070a3
      https://github.com/llvm/llvm-project/commit/7190fa6b16442e24a46a61357fc02f2e268070a3
  Author: Shilei Tian <i at tianshilei.me>
  Date:   2025-03-30 (Sun, 30 Mar 2025)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIISelLowering.cpp
    A llvm/test/CodeGen/AMDGPU/inreg-vgpr-spill.ll

  Log Message:
  -----------
  [WIP][AMDGPU] Improve the handling of `inreg` arguments

When SGPRs available for `inreg` argument passing run out, the compiler silently
falls back to using whole VGPRs to pass those arguments. Ideally, instead of
using whole VGPRs, we should pack `inreg` arguments into individual lanes of
VGPRs.

This PR introduces `InregVGPRSpiller`, which handles this packing. It uses
`v_writelane` at the call site to place `inreg` arguments into specific VGPR
lanes, and then extracts them in the callee using `v_readlane`.

Fixes #130443 and #129071.



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