Re: [PATCH] RISC-V: decouple stack allocation for rv32e w/o save-restore.

[Jeff Law <jeffreyalaw@gmail.com>]

On 4/21/23 04:07, Fei Gao wrote:
> Currently in rv32e, stack allocation for GPR callee-saved registers is
> always 12 bytes w/o save-restore. Actually, for the case without save-restore,
> less stack memory can be reserved. This patch decouples stack allocation for
> rv32e w/o save-restore and makes riscv_compute_frame_info more readable.
> 
> output of testcase rv32e_stack.c
> before patch:
> 	addi	sp,sp,-16
> 	sw	ra,12(sp)
> 	call	getInt
> 	sw	a0,0(sp)
> 	lw	a0,0(sp)
> 	call	PrintInts
> 	lw	a5,0(sp)
> 	mv	a0,a5
> 	lw	ra,12(sp)
> 	addi	sp,sp,16
> 	jr	ra
> 
> after patch:
> 	addi	sp,sp,-8
> 	sw	ra,4(sp)
> 	call	getInt
> 	sw	a0,0(sp)
> 	lw	a0,0(sp)
> 	call	PrintInts
> 	lw	a5,0(sp)
> 	mv	a0,a5
> 	lw	ra,4(sp)
> 	addi	sp,sp,8
> 	jr	ra
> 
> gcc/ChangeLog:
> 
>          * config/riscv/riscv.cc (riscv_forbid_save_libcall): helper function for riscv_use_save_libcall.
>          (riscv_use_save_libcall): call riscv_forbid_save_libcall.
>          (riscv_compute_frame_info): restructure to decouple stack allocation for rv32e w/o save-restore.
> 
> gcc/testsuite/ChangeLog:
> 
>          * gcc.target/riscv/rv32e_stack.c: New test.
> ---
>   gcc/config/riscv/riscv.cc                    | 57 ++++++++++++--------
>   gcc/testsuite/gcc.target/riscv/rv32e_stack.c | 14 +++++
>   2 files changed, 49 insertions(+), 22 deletions(-)
>   create mode 100644 gcc/testsuite/gcc.target/riscv/rv32e_stack.c
> 
> diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
> index 5d2550871c7..6ccdfe96fe7 100644
> --- a/gcc/config/riscv/riscv.cc
> +++ b/gcc/config/riscv/riscv.cc
> @@ -4772,12 +4772,26 @@ riscv_save_reg_p (unsigned int regno)
>     return false;
>   }
>   
> +/* Determine whether to disable GPR save/restore routines.  */
> +static bool
> +riscv_forbid_save_libcall (void)
I would suggest something like this for the function comment:

/* Return TRUE if a libcall to save/restore GPRs should be
    avoided.  FALSE otherwise.  */

I would also change the name from "forbid" to "avoid".


With those changes I think this will be ready for the trunk.  So repost 
after those changes and I'll get it pushed into the trunk.

Thanks,
Jeff