[all-commits] [llvm/llvm-project] a959ad: [AArch64][GISel] Assign G_LOAD defs into FPR if th...

[Him188 via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a959ad155343095fc8f73aa397a72e3ced1df354
      https://github.com/llvm/llvm-project/commit/a959ad155343095fc8f73aa397a72e3ced1df354
  Author: Him188 <tguan at nvidia.com>
  Date:   2024-06-13 (Thu, 13 Jun 2024)

  Changed paths:
    M llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.cpp
    M llvm/lib/Target/AArch64/GISel/AArch64RegisterBankInfo.h
    M llvm/test/CodeGen/AArch64/GlobalISel/regbank-fp-use-def.mir
    M llvm/test/CodeGen/AArch64/GlobalISel/regbankselect-fp-loads.mir

  Log Message:
  -----------
  [AArch64][GISel] Assign G_LOAD defs into FPR if they feed FP instructions indirectly via PHI (#94618)

If G_LOAD def is used by a PHI, recursively check if the def of PHI is
used by any instruction that only uses FP oprand. If so, assign the def
of G_LOAD to FPR.

In other words, this change helps RBS to assign G_LOAD defs into FPR if
they are later on used in an FP instruction **indirectly via PHI**, to
avoid unnecessary copies. Before this patch, we only considered direct
usages.

It helps to fix GISel regression in TSVC kernel s3110.
GISel was 50% slower than SDAG before this change. Now GISel and SDAG
have the same runtime.



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