tree 999685b698a9352c41df9b58f384b7b4454c9c11
parent 7d52167b4ab6e0eca8041dc67546f9d1dd4909a3
author Scott Linder <Scott.Linder@amd.com> 1579645677 -0500
committer Copybara-Service <copybara-worker@google.com> 1603360399 -0700

[AMDGPU] Add Scratch Wave Offset to Scratch Buffer Descriptor in entry functions

Add the scratch wave offset to the scratch buffer descriptor (SRSrc) in
the entry function prologue. This allows us to removes the scratch wave
offset register from the calling convention ABI.

As part of this change, allow the use of an inline constant zero for the
SOffset of MUBUF instructions accessing the stack in entry functions
when a frame pointer is not requested/required. Entry functions with
calls still need to set up the calling convention ABI stack pointer
register, and reference it in order to address arguments of called
functions. The ABI stack pointer register remains unswizzled, but is now
wave-relative instead of queue-relative.

Non-entry functions also use an inline constant zero SOffset for
wave-relative scratch access, but continue to use the stack and frame
pointers as before. When the stack or frame pointer is converted to a
swizzled offset it is now scaled directly, as the scratch wave offset no
longer needs to be subtracted first.

Update llvm/docs/AMDGPUUsage.rst to reflect these changes to the calling
convention.

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75138

GitOrigin-RevId: 60b1967c3933c42f473a3f7be5f40747547b6057