[U-Boot] [PATCH 07/30] riscv: set -march and -mabi based on the Kconfig configuration

[Bin Meng]

Hi Lukas,

On Sat, Oct 20, 2018 at 6:09 AM Lukas Auer
<lukas.auer at aisec.fraunhofer.de> wrote:
>
> Use the new Kconfig entries to construct the ISA string for the -march
> compiler flag. The -mabi compiler flag is selected based on the base
> integer instruction set.
>
> With this change, the C (compressed instructions) ISA extension is now
> enabled for all boards with CONFIG_RISCV_ISA_C set. Buildman reports a
> decrease in binary size of 71590 bytes.
>
> Signed-off-by: Lukas Auer <lukas.auer at aisec.fraunhofer.de>
> ---
>
>  arch/riscv/Makefile  | 13 +++++++++++++
>  arch/riscv/config.mk |  4 ----
>  2 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 8fb6a889d8..6fb292d0b4 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -3,6 +3,19 @@
>  # Copyright (C) 2017 Andes Technology Corporation.
>  # Rick Chen, Andes Technology Corporation <rick at andestech.com>
>
> +riscv-march-$(CONFIG_ARCH_RV32I)       := rv32im
> +riscv-march-$(CONFIG_ARCH_RV64I)       := rv64im
> +riscv-march-$(CONFIG_RISCV_ISA_A)      := $(riscv-march-y)a
> +riscv-march-$(CONFIG_RISCV_ISA_C)      := $(riscv-march-y)c
> +
> +riscv-mabi-$(CONFIG_ARCH_RV64I)        := lp64
> +riscv-mabi-$(CONFIG_ARCH_RV32I)        := ilp32
> +
> +arch-y := -march=$(riscv-march-y) -mabi=$(riscv-mabi-y)
> +
> +PLATFORM_CPPFLAGS      += $(arch-y)
> +CFLAGS_EFI             += $(arch-y)
> +

The concept of this patch is good. However the usage of := is a bit
odd, since it makes people think the latter will override the former
one, however it is not.

Can we get rid of these riscv-mach-xxx, instead using something like this:

ifeq ($(CONFIG_RISCV_ISA_A),y)
        ARCH_A = a
endif
ifeq ($(CONFIG_RISCV_ISA_C),y)
        ARCH_C = c
endif

ifeq ($(CONFIG_ARCH_RV32I),y)
        BITS = 32
        ABI_I = i
endif
ifeq ($(CONFIG_ARCH_RV64I),y)
        BITS = 64
endif

PLATFORM_CPPFLAGS += -march=rv$(BITS)im$(ARCH_A)$(ARCH_C)
-mabi=$(ABI_I)lp$(BITS)

>  head-y := arch/riscv/cpu/start.o
>
>  libs-y += arch/riscv/cpu/
> diff --git a/arch/riscv/config.mk b/arch/riscv/config.mk
> index ed9eb0c24c..9088b9ef2c 100644
> --- a/arch/riscv/config.mk
> +++ b/arch/riscv/config.mk
> @@ -14,16 +14,12 @@
>  64bit-emul             := elf64lriscv
>
>  ifdef CONFIG_32BIT
> -PLATFORM_CPPFLAGS      += -march=rv32ima -mabi=ilp32
>  PLATFORM_LDFLAGS       += -m $(32bit-emul)
> -CFLAGS_EFI             += -march=rv32ima -mabi=ilp32
>  EFI_LDS                        := elf_riscv32_efi.lds
>  endif
>
>  ifdef CONFIG_64BIT
> -PLATFORM_CPPFLAGS      += -march=rv64ima -mabi=lp64
>  PLATFORM_LDFLAGS       += -m $(64bit-emul)
> -CFLAGS_EFI             += -march=rv64ima -mabi=lp64
>  EFI_LDS                        := elf_riscv64_efi.lds
>  endif
>
> --

Regards,
Bin