[PATCH 1/1] riscv: support building double-float modules

[Rick Chen]

HI Heinrich

> >> From: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> >> Sent: Saturday, October 08, 2022 5:18 PM
> >> To: Rick Jian-Zhi Chen(陳建志) <rick at andestech.com>; Leo Yu-Chi Liang(梁育齊) <ycliang at andestech.com>
> >> Cc: Tom Rini <trini at konsulko.com>; u-boot at lists.denx.de; Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> >> Subject: [PATCH 1/1] riscv: support building double-float modules
> >>
> >> The riscv32 toolchain for GCC-12 provided by kernel.org contains libgcc.a compiled for double-float. To link to it we have to adjust how we build U-Boot.
> >>
> >> As U-Boot actually does not use floating point at all this should not make a significant difference for the produced binaries.
> >>
> >> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> >> ---
> >>   arch/riscv/Kconfig  | 14 ++++++++++++++  arch/riscv/Makefile | 17 ++++++++++++++---
> >>   2 files changed, 28 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 32a90b83b5..8add95c8ef 100644
> >> --- a/arch/riscv/Kconfig
> >> +++ b/arch/riscv/Kconfig
> >> @@ -152,6 +152,20 @@ config RISCV_ISA_C
> >>            when building U-Boot, which results in compressed instructions in the
> >>            U-Boot binary.
> >>
> >> +config RISCV_ISA_F
> >> +       bool "Standard extension for Single-Precision Floating Point"
> >> +       default y
> >
> >
> > Shall this default y need to depend on RV32 ?
>
> All RV64 boards that we currently support have the F and D extension and
> these extensions are in RV64GC. There is no need to disable the F option
> on RV64.
>
> If you wanted to catch if anybody is using floating point calculation in
> U-Boot, we could let it depend on RV32 until we hit another libgcc pitfall.

OK, let's keep no change here.
Thanks for your explanation.

Thanks,
Rick

>
> Best regards
>
> Heinrich
>
> >
> > Reviewed-by: Rick Chen <rick at andestech.com>
> >
> >> +       help
> >> +         Adds "F" to the ISA string passed to the compiler.
> >> +
> >> +config RISCV_ISA_D
> >> +       bool "Standard extension forr Double-Precision Floating Point"
> >> +       depends on RISCV_ISA_F
> >> +       default y
> >> +       help
> >> +         Adds "D" to the ISA string passed to the compiler and changes the
> >> +         riscv32 ABI from ilp32 to ipl32d.
> >> +
> >>   config RISCV_ISA_A
> >>          def_bool y
> >>
> >> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index 53d1194ffb..d1b6e86dd8 100644
> >> --- a/arch/riscv/Makefile
> >> +++ b/arch/riscv/Makefile
> >> @@ -5,15 +5,24 @@
> >>
> >>   ifeq ($(CONFIG_ARCH_RV64I),y)
> >>          ARCH_BASE = rv64im
> >> -       ABI = lp64
> >> +       ABI_BASE = lp64
> >>   endif
> >>   ifeq ($(CONFIG_ARCH_RV32I),y)
> >>          ARCH_BASE = rv32im
> >> -       ABI = ilp32
> >> +       ABI_BASE = ilp32
> >>   endif
> >>   ifeq ($(CONFIG_RISCV_ISA_A),y)
> >>          ARCH_A = a
> >>   endif
> >> +ifeq ($(CONFIG_RISCV_ISA_F),y)
> >> +       ARCH_F = f
> >> +endif
> >> +ifeq ($(CONFIG_RISCV_ISA_D),y)
> >> +       ARCH_D = d
> >> +ifeq ($(CONFIG_ARCH_RV32I),y)
> >> +       ABI_D = d
> >> +endif
> >> +endif
> >>   ifeq ($(CONFIG_RISCV_ISA_C),y)
> >>          ARCH_C = c
> >>   endif
> >> @@ -24,7 +33,9 @@ ifeq ($(CONFIG_CMODEL_MEDANY),y)
> >>          CMODEL = medany
> >>   endif
> >>
> >> -RISCV_MARCH = $(ARCH_BASE)$(ARCH_A)$(ARCH_C)
> >> +
> >> +RISCV_MARCH = $(ARCH_BASE)$(ARCH_A)$(ARCH_F)$(ARCH_D)$(ARCH_C)
> >> +ABI = $(ABI_BASE)$(ABI_D)
> >>
> >>   # Newer binutils versions default to ISA spec version 20191213 which moves some  # instructions from the I extension to the Zicsr and Zifencei extensions.
> >> --