[Buildroot] [PATCH 1/1] arch/riscv: set the default float ABI based on ISA extensions

[Buildroot] [PATCH 1/1] arch/riscv: set the default float ABI based on ISA extensions

[Mark Corbin]

This patch sets the default floating point ABI based on the ISA
extensions that have been selected rather than defaulting to soft
float.

For 64-bit:

ISA 'D' selects  lp64d
ISA 'F' selects  lp64f
Otherwise select lp64

For 32-bit:

ISA 'D' selects  ilp32d
ISA 'F' selects  ilp32f
Otherwise select ilp32

This change was proposed by Palmer Dabbelt at SiFive.

Signed-off-by: Mark Corbin <mark.corbin@embecosm.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
---
 arch/Config.in.riscv | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/Config.in.riscv b/arch/Config.in.riscv
index bdd2672602..1fc20e5de7 100644
--- a/arch/Config.in.riscv
+++ b/arch/Config.in.riscv
@@ -80,8 +80,12 @@ endchoice
 
 choice
 	prompt "Target ABI"
-	default BR2_RISCV_ABI_ILP32 if !BR2_ARCH_IS_64
-	default BR2_RISCV_ABI_LP64 if BR2_ARCH_IS_64
+	default BR2_RISCV_ABI_ILP32D if !BR2_ARCH_IS_64 && BR2_RISCV_ISA_RVD
+	default BR2_RISCV_ABI_ILP32F if !BR2_ARCH_IS_64 && BR2_RISCV_ISA_RVF
+	default BR2_RISCV_ABI_ILP32  if !BR2_ARCH_IS_64
+	default BR2_RISCV_ABI_LP64D  if BR2_ARCH_IS_64 && BR2_RISCV_ISA_RVD
+	default BR2_RISCV_ABI_LP64F  if BR2_ARCH_IS_64 && BR2_RISCV_ISA_RVF
+	default BR2_RISCV_ABI_LP64   if BR2_ARCH_IS_64
 
 config BR2_RISCV_ABI_ILP32
 	bool "ilp32"
-- 
2.19.1

[Buildroot] [PATCH 1/1] arch/riscv: set the default float ABI based on ISA extensions

[Thomas Petazzoni]

Hello Mark,

On Thu, 19 Sep 2019 16:40:35 +0100
Mark Corbin <mark.corbin@embecosm.com> wrote:

> This patch sets the default floating point ABI based on the ISA
> extensions that have been selected rather than defaulting to soft
> float.
> 
> For 64-bit:
> 
> ISA 'D' selects  lp64d
> ISA 'F' selects  lp64f
> Otherwise select lp64
> 
> For 32-bit:
> 
> ISA 'D' selects  ilp32d
> ISA 'F' selects  ilp32f
> Otherwise select ilp32
> 
> This change was proposed by Palmer Dabbelt at SiFive.
> 
> Signed-off-by: Mark Corbin <mark.corbin@embecosm.com>
> Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
> ---
>  arch/Config.in.riscv | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

Applied to master, thanks. However, I'm wondering: does it really makes
sense to offer a choice of the ABI ? Would there be a reason for a user
to use lp64 if he has the D ISA for example ? It would seem logical to
simply use lp64d as soon as you have the D ISA.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com