[PATCH] D125409: [AMDGPU] Revert wide LDS DMA support.

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

rampitec added inline comments.


================
Comment at: llvm/test/MC/AMDGPU/mubuf.s:850
-
-buffer_load_dwordx3 off, s[4:7], s0 offset:4095 lds
-// NOSICI: error: not a valid operand
----------------
foad wrote:
> arsenm wrote:
> > If it actually does something, shouldn't the assembler/disassembler still recognize it? We just wouldn't continue selecting
> All the documentation I've seen says you're not allowed to use the lds bit on larger-than-dword loads. Then again, this all comes from https://bugs.llvm.org/show_bug.cgi?id=37653 which says it is a "potentially useful //but still undocumented// feature"...
Right, all the documentation says it is not allowed. For example https://developer.amd.com/wp-content/resources/Vega_Shader_ISA_28July2017.pdf, 8.1.9 Memory Buffer Load to LDS:

The MUBUF instruction format allows reading data from a memory buffer directly into LDS
without passing through VGPRs. This is supported for the following subset of MUBUF
instructions.
• BUFFER_LOAD_{ubyte, sbyte, ushort, sshort, dword, format_x}.

For a wider operands it does something, but that something data race on store to LDS and corrupted output.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D125409/new/

https://reviews.llvm.org/D125409