diff mbox series

[5/5] MIPS: Fallback CPU -march CFLAG to ISA level if unsupported

Message ID 20230407102721.14814-6-jiaxun.yang@flygoat.com (mailing list archive)
State Superseded
Headers show
Series MIPS: LLVM toolchain support for more CPUs | expand

Commit Message

Jiaxun Yang April 7, 2023, 10:27 a.m. UTC 
LLVM does not implement some of -march option. However those march
does not provide any special functionality in most cases, they just
serves as compiler's tuning target.

Fallback -march CFLAG to ISA level if unsupported by toolchain so
we can get those kernel to build with LLVM.

Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
 arch/mips/Makefile | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

Comments

Nick Desaulniers April 7, 2023, 10:23 p.m. UTC | #1 
On Fri, Apr 7, 2023 at 3:27 AM Jiaxun Yang <jiaxun.yang@flygoat.com> wrote:
>
> LLVM does not implement some of -march option. However those march
> does not provide any special functionality in most cases, they just
> serves as compiler's tuning target.

Then should we change these then to be in the form:

-cflags-$(CONFIG_CPU_R3000)     += -march=r3000
+cflags-$(CONFIG_CPU_R3000)     += -march=mips1 $(call cc-option,-mtune=r3000)

>
> Fallback -march CFLAG to ISA level if unsupported by toolchain so
> we can get those kernel to build with LLVM.
>
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> ---
>  arch/mips/Makefile | 30 +++++++++++++++++-------------
>  1 file changed, 17 insertions(+), 13 deletions(-)
>
> diff --git a/arch/mips/Makefile b/arch/mips/Makefile
> index 344fe5f00f7b..eab6abeaa45c 100644
> --- a/arch/mips/Makefile
> +++ b/arch/mips/Makefile
> @@ -148,10 +148,10 @@ cflags-y += $(call cc-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
>  #
>  # CPU-dependent compiler/assembler options for optimization.
>  #
> -cflags-$(CONFIG_CPU_R3000)     += -march=r3000
> -cflags-$(CONFIG_CPU_R4300)     += -march=r4300 -Wa,--trap
> -cflags-$(CONFIG_CPU_R4X00)     += -march=r4600 -Wa,--trap
> -cflags-$(CONFIG_CPU_TX49XX)    += -march=r4600 -Wa,--trap
> +cflags-$(CONFIG_CPU_R3000)     += $(call cc-option,-march=r3000,-march=mips1)
> +cflags-$(CONFIG_CPU_R4300)     += $(call cc-option,-march=r4300,-march=mips3) -Wa,--trap
> +cflags-$(CONFIG_CPU_R4X00)     += $(call cc-option,-march=r4600,-march=mips3) -Wa,--trap
> +cflags-$(CONFIG_CPU_TX49XX)    += $(call cc-option,-march=r4600,-march=mips3) -Wa,--trap
>  cflags-$(CONFIG_CPU_MIPS32_R1) += -march=mips32 -Wa,--trap
>  cflags-$(CONFIG_CPU_MIPS32_R2) += -march=mips32r2 -Wa,--trap
>  cflags-$(CONFIG_CPU_MIPS32_R5) += -march=mips32r5 -Wa,--trap -modd-spreg
> @@ -160,19 +160,21 @@ cflags-$(CONFIG_CPU_MIPS64_R1)    += -march=mips64 -Wa,--trap
>  cflags-$(CONFIG_CPU_MIPS64_R2) += -march=mips64r2 -Wa,--trap
>  cflags-$(CONFIG_CPU_MIPS64_R5) += -march=mips64r5 -Wa,--trap
>  cflags-$(CONFIG_CPU_MIPS64_R6) += -march=mips64r6 -Wa,--trap
> -cflags-$(CONFIG_CPU_P5600)     += -march=p5600 -Wa,--trap -modd-spreg
> -cflags-$(CONFIG_CPU_R5000)     += -march=r5000 -Wa,--trap
> -cflags-$(CONFIG_CPU_R5500)     += $(call cc-option,-march=r5500,-march=r5000) \
> +cflags-$(CONFIG_CPU_P5600)     += $(call cc-option,-march=p5600,-march=mips32r5) \
> +                       -Wa,--trap -modd-spreg
> +cflags-$(CONFIG_CPU_R5000)     += $(call cc-option,-march=r5000,-march=mips4) \
>                         -Wa,--trap
> -cflags-$(CONFIG_CPU_NEVADA)    += $(call cc-option,-march=rm5200,-march=r5000) \
> +cflags-$(CONFIG_CPU_R5500)     += $(call cc-option,-march=r5500,-march=mips4) \
>                         -Wa,--trap
> -cflags-$(CONFIG_CPU_RM7000)    += $(call cc-option,-march=rm7000,-march=r5000) \
> +cflags-$(CONFIG_CPU_NEVADA)    += $(call cc-option,-march=rm5200,-march=mips4) \
>                         -Wa,--trap
> -cflags-$(CONFIG_CPU_SB1)       += $(call cc-option,-march=sb1,-march=r5000) \
> +cflags-$(CONFIG_CPU_RM7000)    += $(call cc-option,-march=rm7000,-march=mips4) \
> +                       -Wa,--trap
> +cflags-$(CONFIG_CPU_SB1)       += $(call cc-option,-march=sb1,-march=mips4) \
>                         -Wa,--trap
>  cflags-$(CONFIG_CPU_SB1)       += $(call cc-option,-mno-mdmx)
>  cflags-$(CONFIG_CPU_SB1)       += $(call cc-option,-mno-mips3d)
> -cflags-$(CONFIG_CPU_R10000)    += $(call cc-option,-march=r10000,-march=r8000) \
> +cflags-$(CONFIG_CPU_R10000)    += $(call cc-option,-march=r10000,-march=mips4) \
>                         -Wa,--trap
>  cflags-$(CONFIG_CPU_CAVIUM_OCTEON) += $(call cc-option,-march=octeon) -Wa,--trap
>  ifeq (,$(findstring march=octeon, $(cflags-$(CONFIG_CPU_CAVIUM_OCTEON))))
> @@ -181,8 +183,10 @@ endif
>  cflags-$(CONFIG_CAVIUM_CN63XXP1) += -Wa,-mfix-cn63xxp1
>  cflags-$(CONFIG_CPU_BMIPS)     += -march=mips32 -Wa,-mips32 -Wa,--trap
>
> -cflags-$(CONFIG_CPU_LOONGSON2E) += -march=loongson2e -Wa,--trap
> -cflags-$(CONFIG_CPU_LOONGSON2F) += -march=loongson2f -Wa,--trap
> +cflags-$(CONFIG_CPU_LOONGSON2E) += \
> +                       $(call cc-option,-march=loongson2e,-march=mips3) -Wa,--trap
> +cflags-$(CONFIG_CPU_LOONGSON2F) += \
> +                       $(call cc-option,-march=loongson2f,-march=mips3) -Wa,--trap
>  # Some -march= flags enable MMI instructions, and GCC complains about that
>  # support being enabled alongside -msoft-float. Thus explicitly disable MMI.
>  cflags-$(CONFIG_CPU_LOONGSON2EF) += $(call cc-option,-mno-loongson-mmi)
> --
> 2.39.2 (Apple Git-143)
>
Jiaxun Yang April 8, 2023, 9:47 a.m. UTC | #2 
> 2023年4月7日 23:23，Nick Desaulniers <ndesaulniers@google.com> 写道：
> 
> On Fri, Apr 7, 2023 at 3:27 AM Jiaxun Yang <jiaxun.yang@flygoat.com> wrote:
>> 
>> LLVM does not implement some of -march option. However those march
>> does not provide any special functionality in most cases, they just
>> serves as compiler's tuning target.
> 
> Then should we change these then to be in the form:
> 
> -cflags-$(CONFIG_CPU_R3000)     += -march=r3000
> +cflags-$(CONFIG_CPU_R3000)     += -march=mips1 $(call cc-option,-mtune=r3000)

Just tested with GCC and it seems like there are still some difference in generated code
for -march=r4600 and -march=mips3 -mtune=r4600.
As I’m unable to test on a real system I’d prefer just leave them as is.

I’ll try to reword commit message.

Thanks
Jiaxun

> 
> -- 
> Thanks,
> ~Nick Desaulniers
diff mbox series

Patch

diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index 344fe5f00f7b..eab6abeaa45c 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -148,10 +148,10 @@  cflags-y += $(call cc-option,-Wa$(comma)-mno-fix-loongson3-llsc,)
 #
 # CPU-dependent compiler/assembler options for optimization.
 #
-cflags-$(CONFIG_CPU_R3000)	+= -march=r3000
-cflags-$(CONFIG_CPU_R4300)	+= -march=r4300 -Wa,--trap
-cflags-$(CONFIG_CPU_R4X00)	+= -march=r4600 -Wa,--trap
-cflags-$(CONFIG_CPU_TX49XX)	+= -march=r4600 -Wa,--trap
+cflags-$(CONFIG_CPU_R3000)	+= $(call cc-option,-march=r3000,-march=mips1)
+cflags-$(CONFIG_CPU_R4300)	+= $(call cc-option,-march=r4300,-march=mips3) -Wa,--trap
+cflags-$(CONFIG_CPU_R4X00)	+= $(call cc-option,-march=r4600,-march=mips3) -Wa,--trap
+cflags-$(CONFIG_CPU_TX49XX)	+= $(call cc-option,-march=r4600,-march=mips3) -Wa,--trap
 cflags-$(CONFIG_CPU_MIPS32_R1)	+= -march=mips32 -Wa,--trap
 cflags-$(CONFIG_CPU_MIPS32_R2)	+= -march=mips32r2 -Wa,--trap
 cflags-$(CONFIG_CPU_MIPS32_R5)	+= -march=mips32r5 -Wa,--trap -modd-spreg
@@ -160,19 +160,21 @@  cflags-$(CONFIG_CPU_MIPS64_R1)	+= -march=mips64 -Wa,--trap
 cflags-$(CONFIG_CPU_MIPS64_R2)	+= -march=mips64r2 -Wa,--trap
 cflags-$(CONFIG_CPU_MIPS64_R5)	+= -march=mips64r5 -Wa,--trap
 cflags-$(CONFIG_CPU_MIPS64_R6)	+= -march=mips64r6 -Wa,--trap
-cflags-$(CONFIG_CPU_P5600)	+= -march=p5600 -Wa,--trap -modd-spreg
-cflags-$(CONFIG_CPU_R5000)	+= -march=r5000 -Wa,--trap
-cflags-$(CONFIG_CPU_R5500)	+= $(call cc-option,-march=r5500,-march=r5000) \
+cflags-$(CONFIG_CPU_P5600)	+= $(call cc-option,-march=p5600,-march=mips32r5) \
+			-Wa,--trap -modd-spreg
+cflags-$(CONFIG_CPU_R5000)	+= $(call cc-option,-march=r5000,-march=mips4) \
 			-Wa,--trap
-cflags-$(CONFIG_CPU_NEVADA)	+= $(call cc-option,-march=rm5200,-march=r5000) \
+cflags-$(CONFIG_CPU_R5500)	+= $(call cc-option,-march=r5500,-march=mips4) \
 			-Wa,--trap
-cflags-$(CONFIG_CPU_RM7000)	+= $(call cc-option,-march=rm7000,-march=r5000) \
+cflags-$(CONFIG_CPU_NEVADA)	+= $(call cc-option,-march=rm5200,-march=mips4) \
 			-Wa,--trap
-cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-march=sb1,-march=r5000) \
+cflags-$(CONFIG_CPU_RM7000)	+= $(call cc-option,-march=rm7000,-march=mips4) \
+			-Wa,--trap
+cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-march=sb1,-march=mips4) \
 			-Wa,--trap
 cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-mno-mdmx)
 cflags-$(CONFIG_CPU_SB1)	+= $(call cc-option,-mno-mips3d)
-cflags-$(CONFIG_CPU_R10000)	+= $(call cc-option,-march=r10000,-march=r8000) \
+cflags-$(CONFIG_CPU_R10000)	+= $(call cc-option,-march=r10000,-march=mips4) \
 			-Wa,--trap
 cflags-$(CONFIG_CPU_CAVIUM_OCTEON) += $(call cc-option,-march=octeon) -Wa,--trap
 ifeq (,$(findstring march=octeon, $(cflags-$(CONFIG_CPU_CAVIUM_OCTEON))))
@@ -181,8 +183,10 @@  endif
 cflags-$(CONFIG_CAVIUM_CN63XXP1) += -Wa,-mfix-cn63xxp1
 cflags-$(CONFIG_CPU_BMIPS)	+= -march=mips32 -Wa,-mips32 -Wa,--trap
 
-cflags-$(CONFIG_CPU_LOONGSON2E) += -march=loongson2e -Wa,--trap
-cflags-$(CONFIG_CPU_LOONGSON2F) += -march=loongson2f -Wa,--trap
+cflags-$(CONFIG_CPU_LOONGSON2E) += \
+			$(call cc-option,-march=loongson2e,-march=mips3) -Wa,--trap
+cflags-$(CONFIG_CPU_LOONGSON2F) += \
+			$(call cc-option,-march=loongson2f,-march=mips3) -Wa,--trap
 # Some -march= flags enable MMI instructions, and GCC complains about that
 # support being enabled alongside -msoft-float. Thus explicitly disable MMI.
 cflags-$(CONFIG_CPU_LOONGSON2EF) += $(call cc-option,-mno-loongson-mmi)