LGTM, I think long jump is another issue and making ra become a fixed
register will escalate to an ABI issue, so that should not be a
blocker for this patch.
On Tue, Jul 18, 2023 at 4:10 PM yanzhang.wang--- via Gcc-patches
wrote:
>
> From: Yanzhang Wang
>
> gcc/ChangeLog:
>
> * config/riscv/riscv.cc (riscv_save_reg_p): Save ra for leaf
> when enabling -mno-omit-leaf-frame-pointer
> (riscv_option_override): Override omit-frame-pointer.
> (riscv_frame_pointer_required): Save s0 for non-leaf function
> (TARGET_FRAME_POINTER_REQUIRED): Override defination
> * config/riscv/riscv.opt: Add option support.
>
> gcc/testsuite/ChangeLog:
>
> * gcc.target/riscv/omit-frame-pointer-1.c: New test.
> * gcc.target/riscv/omit-frame-pointer-2.c: New test.
> * gcc.target/riscv/omit-frame-pointer-3.c: New test.
> * gcc.target/riscv/omit-frame-pointer-4.c: New test.
> * gcc.target/riscv/omit-frame-pointer-test.c: New test.
>
> Signed-off-by: Yanzhang Wang
> ---
> gcc/config/riscv/riscv.cc | 34 ++-
> gcc/config/riscv/riscv.opt| 4 +++
> .../gcc.target/riscv/omit-frame-pointer-1.c | 7
> .../gcc.target/riscv/omit-frame-pointer-2.c | 7
> .../gcc.target/riscv/omit-frame-pointer-3.c | 7
> .../gcc.target/riscv/omit-frame-pointer-4.c | 7
> .../riscv/omit-frame-pointer-test.c | 13 +++
> 7 files changed, 78 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.target/riscv/omit-frame-pointer-1.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/omit-frame-pointer-2.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/omit-frame-pointer-3.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/omit-frame-pointer-4.c
> create mode 100644 gcc/testsuite/gcc.target/riscv/omit-frame-pointer-test.c
>
> diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
> index 706c18416db..caae6168c29 100644
> --- a/gcc/config/riscv/riscv.cc
> +++ b/gcc/config/riscv/riscv.cc
> @@ -379,6 +379,10 @@ static const struct riscv_tune_info
> riscv_tune_info_table[] = {
> #include "riscv-cores.def"
> };
>
> +/* Global variable to distinguish whether we should save and restore s0/fp
> for
> + function. */
> +static bool riscv_save_frame_pointer;
> +
> void riscv_frame_info::reset(void)
> {
>total_size = 0;
> @@ -4948,7 +4952,11 @@ riscv_save_reg_p (unsigned int regno)
>if (regno == HARD_FRAME_POINTER_REGNUM && frame_pointer_needed)
> return true;
>
> - if (regno == RETURN_ADDR_REGNUM && crtl->calls_eh_return)
> + /* Need not to use ra for leaf when frame pointer is turned off by option
> + whatever the omit-leaf-frame's value. */
> + bool keep_leaf_ra = frame_pointer_needed && crtl->is_leaf
> +&& !TARGET_OMIT_LEAF_FRAME_POINTER;
> + if (regno == RETURN_ADDR_REGNUM && (crtl->calls_eh_return || keep_leaf_ra))
> return true;
>
>/* If this is an interrupt handler, then must save extra registers. */
> @@ -6577,6 +6585,21 @@ riscv_option_override (void)
>if (flag_pic)
> riscv_cmodel = CM_PIC;
>
> + /* We need to save the fp with ra for non-leaf functions with no fp and ra
> + for leaf functions while no-omit-frame-pointer with
> + omit-leaf-frame-pointer. The x_flag_omit_frame_pointer has the first
> + priority to determine whether the frame pointer is needed. If we do not
> + override it, the fp and ra will be stored for leaf functions, which is
> not
> + our wanted. */
> + riscv_save_frame_pointer = false;
> + if (TARGET_OMIT_LEAF_FRAME_POINTER_P (global_options.x_target_flags))
> +{
> + if (!global_options.x_flag_omit_frame_pointer)
> + riscv_save_frame_pointer = true;
> +
> + global_options.x_flag_omit_frame_pointer = 1;
> +}
> +
>/* We get better code with explicit relocs for CM_MEDLOW, but
> worse code for the others (for now). Pick the best default. */
>if ((target_flags_explicit & MASK_EXPLICIT_RELOCS) == 0)
> @@ -7857,6 +7880,12 @@ riscv_preferred_else_value (unsigned, tree, unsigned
> int nops, tree *ops)
>return nops == 3 ? ops[2] : ops[0];
> }
>
> +static bool
> +riscv_frame_pointer_required (void)
> +{
> + return riscv_save_frame_pointer && !crtl->is_leaf;
> +}
> +
> /* Initialize the GCC target structure. */
> #undef TARGET_ASM_ALIGNED_HI_OP
> #define TARGET_ASM_ALIGNED_HI_OP "\t.half\t"
> @@ -8161,6 +8190,9 @@ riscv_preferred_else_value (unsigned, tree, unsigned
> int nops, tree *ops)
> #undef TARGET_PREFERRED_ELSE_VALUE
> #define TARGET_PREFERRED_ELSE_VALUE riscv_preferred_else_value
>
> +#undef TARGET_FRAME_POINTER_REQUIRED
> +#define TARGET_FRAME_POINTER_REQUIRED riscv_frame_pointer_required
> +
> struct gcc_target targetm = TARGET_INITIALIZER;
>
> #include "gt-riscv.h"
> diff --git a/gcc/config/riscv/riscv.opt b/gcc/config/riscv/riscv.opt
> index dd062f1c8bd..4dfd8f78ad5 100644
> ---
