Felipe Quezada 9deb4fda30
[CodeGen][AMDGPU] TwoAddress: Only skip undef COPY at REG_SEQUENCE lowering when there is Live info or no uses for subreg (#175598)
Currently, the compiler doesn't create a COPY for undef operands while
lowering REG_SEQUENCE, and only if LIS information is available, it
propagates the undef flag to the subreg uses. So, if LIS isn't
available, we can end up with some uses without def of those lanes.
Now, we check which lanes are used in a single scan of
use_nodbg_operands() per REG_SEQ, and perform the skip of the COPY only
if LIS is avaible (as undef will be propagated later) or if there are no
uses for that lane.
There is still a scan of the use list, but now it's only one per REG_SEQ
and I think it's necessary, as there is no guarantee to have LIS or
other analysis pass information at this stage.

This is a proposal fix for issue:
https://github.com/llvm/llvm-project/issues/175596

---------

Co-authored-by: Carl Ritson <critson@perlfu.co.uk>
2026-02-13 08:46:30 -08:00
..
2025-12-05 12:39:50 +00:00
2025-12-05 12:39:50 +00:00
2025-12-05 12:39:50 +00:00

+==============================================================================+
| How to organize the lit tests                                                |
+==============================================================================+

- If you write a test for matching a single DAG opcode or intrinsic, it should
  go in a file called {opcode_name,intrinsic_name}.ll (e.g. fadd.ll)

- If you write a test that matches several DAG opcodes and checks for a single
  ISA instruction, then that test should go in a file called {ISA_name}.ll (e.g.
  bfi_int.ll

- For all other tests, use your best judgement for organizing tests and naming
  the files.

+==============================================================================+
| Naming conventions                                                           |
+==============================================================================+

- Use dash '-' and not underscore '_' to separate words in file names, unless
  the file is named after a DAG opcode or ISA instruction that has an
  underscore '_' in its name.