Matt Arsenault 39bf765bb6
DAG: Use phi to create vregs instead of the constant input (#129464)
For most targets, the register class comes from the type so this
makes no difference. For AMDGPU, the selected register class depends
on the divergence of the value. For a constant phi input, this will
always be false. The heuristic for whether to treat the value as
a scalar or vector constant based on the uses would then incorrectly
think this is a scalar use, when really the phi is a copy from S to V.

This avoids an intermediate s_mov_b32 plus a copy in some cases. These
would often, but not always, fold out in mi passes.

This only adjusts the constant input case. It may make sense to do
this for the non-constant case as well.
2025-03-04 14:44:54 +07:00
..
2024-12-10 10:11:19 +01:00

+==============================================================================+
| 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.