[PATCH 0/3] RISC-V: Add an experimental vector calling convention

[Lehua Ding <lehua.ding@rivai.ai>]

Hi RISC-V folks,

This patch implement the proposal of RISC-V vector calling convention[1] and
this feature can be enabled by `--param=riscv-vector-abi` option. Currently,
all vector type arguments and return values are pass by reference. With this
patch, these arguments and return values can pass through vector registers.
Currently only vector types defined in the RISC-V Vector Extension Intrinsic Document[2]
are supported. GNU-ext vector types are unsupported for now since the
corresponding proposal was not presented.

The proposal introduce a new calling convention variant, functions which follow
this variant need follow the bellow vector register convention.

| Name    | ABI Mnemonic | Meaning                      | Preserved across calls?
=================================================================================
| v0      |              | Argument register            | No
| v1-v7   |              | Callee-saved registers       | Yes
| v8-v23  |              | Argument registers           | No
| v24-v31 |              | Callee-saved registers       | Yes

If a functions follow this vector calling convention, then the function symbole
must be annotated with .variant_cc directive[3] (used to indicate that it is a
calling convention variant).

This implementation split into three parts, each part corresponds to a sub-patch.

- Part-1: Select suitable vector regsiters for vector type arguments and return
  values according to the proposal.
- Part-2: Allocate frame area for callee-saved vector registers and save/restore
  them in prologue and epilogue.
- Part-3: Generate .variant_cc directive for vector function in assembly code.

Best,
Lehua

[1] https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/389
[2] https://github.com/riscv-non-isa/rvv-intrinsic-doc/blob/master/rvv-intrinsic-rfc.md#type-system
[3] https://github.com/riscv-non-isa/riscv-asm-manual/blob/master/riscv-asm.md#pseudo-ops

Lehua Ding (3):
  RISC-V: Part-1: Select suitable vector registers for vector type args
    and returns
  RISC-V: Part-2: Save/Restore vector registers which need to be
    preversed
  RISC-V: Part-3: Output .variant_cc directive for vector function

 gcc/config/riscv/riscv-protos.h               |   4 +
 gcc/config/riscv/riscv-sr.cc                  |  12 +-
 gcc/config/riscv/riscv-vector-builtins.cc     |  10 +
 gcc/config/riscv/riscv.cc                     | 510 ++++++++++++++++--
 gcc/config/riscv/riscv.h                      |  40 ++
 gcc/config/riscv/riscv.md                     |  43 +-
 gcc/config/riscv/riscv.opt                    |   5 +
 .../riscv/rvv/base/abi-call-args-1-run.c      | 127 +++++
 .../riscv/rvv/base/abi-call-args-1.c          | 197 +++++++
 .../riscv/rvv/base/abi-call-args-2-run.c      |  34 ++
 .../riscv/rvv/base/abi-call-args-2.c          |  27 +
 .../riscv/rvv/base/abi-call-args-3-run.c      | 260 +++++++++
 .../riscv/rvv/base/abi-call-args-3.c          | 116 ++++
 .../riscv/rvv/base/abi-call-args-4-run.c      | 145 +++++
 .../riscv/rvv/base/abi-call-args-4.c          | 111 ++++
 .../riscv/rvv/base/abi-call-error-1.c         |  11 +
 .../riscv/rvv/base/abi-call-return-run.c      | 127 +++++
 .../riscv/rvv/base/abi-call-return.c          | 197 +++++++
 .../riscv/rvv/base/abi-call-variant_cc.c      |  39 ++
 .../rvv/base/abi-callee-saved-1-fixed-1.c     |  85 +++
 .../rvv/base/abi-callee-saved-1-fixed-2.c     |  85 +++
 .../riscv/rvv/base/abi-callee-saved-1.c       |  87 +++
 .../riscv/rvv/base/abi-callee-saved-2.c       | 117 ++++
 23 files changed, 2327 insertions(+), 62 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-1-run.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-1.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-2-run.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-2.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-3-run.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-3.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-4-run.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-args-4.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-error-1.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-return-run.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-return.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-call-variant_cc.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-callee-saved-1-fixed-1.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-callee-saved-1-fixed-2.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-callee-saved-1.c
 create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/base/abi-callee-saved-2.c

-- 
2.36.3