[PATCH v2 1/2] MIPS: Loongson64: Clean up use of cc-ifversion

[PATCH v2 1/2] MIPS: Loongson64: Clean up use of cc-ifversion

[Nathan Chancellor]

This Makefile checks that GCC is 4.9 or newer, which is redundant after
commit 76ae847497bc ("Documentation: raise minimum supported version of
GCC to 5.1"), so cc-option can be removed.

Clang does not support -march=loongson3a so it needs to continue to use
-march=mips64r2, which no longer needs cc-option because all supported
clang versions recognize this flag.

-march=loonson3a can be used unconditionally with GCC because the
minimum supported GCC version has been bumped past 4.9.0, which won't
have the bug mentioned in the comment. The _MIPS_ISA macro redefinition
can be removed at the same time for the same reason.

Suggested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---

v1 -> v2: https://lore.kernel.org/r/20220120214001.1879469-1-nathan@kernel.org/

* Eliminate ld-option call (Jiaxun).
* Eliminate _MIPS_ISA macro redefinitions (Nick).

 arch/mips/loongson64/Platform | 21 +++------------------
 1 file changed, 3 insertions(+), 18 deletions(-)

diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform
index 3e660d6d3c2b..f2a08a185ee2 100644
--- a/arch/mips/loongson64/Platform
+++ b/arch/mips/loongson64/Platform
@@ -5,24 +5,9 @@
 
 cflags-$(CONFIG_CPU_LOONGSON64)	+= -Wa,--trap
 
-#
-# binutils from v2.25 on and gcc starting from v4.9.0 treat -march=loongson3a
-# as MIPS64 R2; older versions as just R1.  This leaves the possibility open
-# that GCC might generate R2 code for -march=loongson3a which then is rejected
-# by GAS.  The cc-option can't probe for this behaviour so -march=loongson3a
-# can't easily be used safely within the kbuild framework.
-#
-ifeq ($(call cc-ifversion, -ge, 0409, y), y)
-  ifeq ($(call ld-ifversion, -ge, 22500, y), y)
-    cflags-$(CONFIG_CPU_LOONGSON64)  += \
-      $(call cc-option,-march=loongson3a -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
-  else
-    cflags-$(CONFIG_CPU_LOONGSON64)  += \
-      $(call cc-option,-march=mips64r2,-mips64r2 -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
-  endif
-else
-    cflags-$(CONFIG_CPU_LOONGSON64)  += \
-      $(call cc-option,-march=mips64r2,-mips64r2 -U_MIPS_ISA -D_MIPS_ISA=_MIPS_ISA_MIPS64)
+ifdef CONFIG_CPU_LOONGSON64
+cflags-$(CONFIG_CC_IS_GCC) += -march=loongson3a
+cflags-$(CONFIG_CC_IS_CLANG) += -march=mips64r2
 endif
 
 # Some -march= flags enable MMI instructions, and GCC complains about that

base-commit: e783362eb54cd99b2cac8b3a9aeac942e6f6ac07
-- 
2.35.0

[PATCH v2 2/2] MIPS: Loongson{2ef,64}: Wrap -mno-branch-likely with cc-option

[Nathan Chancellor]

This flag is not supported by clang, which results in a warning:

  clang-14: warning: argument unused during compilation: '-mno-branch-likely' [-Wunused-command-line-argument]

This breaks cc-option, which adds -Werror to make this warning fatal and
catch flags that are not supported.

Wrap this flag in cc-option so that it does not cause cc-option to fail,
which can cause randconfigs to be really noisy, due to warnings not
getting disabled that should be.

Additionally, move the cc-option check to Kconfig so that the check is
done at configuration time, rather than build time, as builds with no
configuration change will be quicker because the cc-option call will not
need to happen in those instances.

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---

v1 -> v2: https://lore.kernel.org/r/20220120214001.1879469-2-nathan@kernel.org/

* Move cc-option call to Kconfig (Nick).
* Also apply to loongson2ef, even though this will not currently build
  with clang.

 arch/mips/Kconfig              | 4 ++++
 arch/mips/loongson2ef/Platform | 3 ++-
 arch/mips/loongson64/Platform  | 3 ++-
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 058446f01487..da6b3e0501a7 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -3202,6 +3202,10 @@ config MIPS32_N32
 
 	  If unsure, say N.
 
+config CC_HAS_MNO_BRANCH_LIKELY
+	def_bool y
+	depends on $(cc-option,-mno-branch-likely)
+
 menu "Power management options"
 
 config ARCH_HIBERNATION_POSSIBLE
diff --git a/arch/mips/loongson2ef/Platform b/arch/mips/loongson2ef/Platform
index 50e659aca543..eebabf9df6ac 100644
--- a/arch/mips/loongson2ef/Platform
+++ b/arch/mips/loongson2ef/Platform
@@ -41,6 +41,7 @@ cflags-y += $(call cc-option,-mno-loongson-mmi)
 # Loongson Machines' Support
 #
 
-cflags-$(CONFIG_MACH_LOONGSON2EF) += -I$(srctree)/arch/mips/include/asm/mach-loongson2ef -mno-branch-likely
+cflags-$(CONFIG_MACH_LOONGSON2EF) += -I$(srctree)/arch/mips/include/asm/mach-loongson2ef
+cflags-$(CONFIG_CC_HAS_MNO_BRANCH_LIKELY) += -mno-branch-likely
 load-$(CONFIG_LEMOTE_FULOONG2E) += 0xffffffff80100000
 load-$(CONFIG_LEMOTE_MACH2F) += 0xffffffff80200000
diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Platform
index f2a08a185ee2..473404cae1c4 100644
--- a/arch/mips/loongson64/Platform
+++ b/arch/mips/loongson64/Platform
@@ -18,5 +18,6 @@ cflags-y += $(call cc-option,-mno-loongson-mmi)
 # Loongson Machines' Support
 #
 
-cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64 -mno-branch-likely
+cflags-$(CONFIG_MACH_LOONGSON64) += -I$(srctree)/arch/mips/include/asm/mach-loongson64
+cflags-$(CONFIG_CC_HAS_MNO_BRANCH_LIKELY) += -mno-branch-likely
 load-$(CONFIG_CPU_LOONGSON64) += 0xffffffff80200000
-- 
2.35.0

Re: [PATCH v2 1/2] MIPS: Loongson64: Clean up use of cc-ifversion

[Thomas Bogendoerfer]

On Tue, Jan 25, 2022 at 03:19:24PM -0700, Nathan Chancellor wrote:
> This Makefile checks that GCC is 4.9 or newer, which is redundant after
> commit 76ae847497bc ("Documentation: raise minimum supported version of
> GCC to 5.1"), so cc-option can be removed.
> 
> Clang does not support -march=loongson3a so it needs to continue to use
> -march=mips64r2, which no longer needs cc-option because all supported
> clang versions recognize this flag.
> 
> -march=loonson3a can be used unconditionally with GCC because the
> minimum supported GCC version has been bumped past 4.9.0, which won't
> have the bug mentioned in the comment. The _MIPS_ISA macro redefinition
> can be removed at the same time for the same reason.
> 
> Suggested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> 
> v1 -> v2: https://lore.kernel.org/r/20220120214001.1879469-1-nathan@kernel.org/
> 
> * Eliminate ld-option call (Jiaxun).
> * Eliminate _MIPS_ISA macro redefinitions (Nick).
> 
>  arch/mips/loongson64/Platform | 21 +++------------------
>  1 file changed, 3 insertions(+), 18 deletions(-)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH v2 2/2] MIPS: Loongson{2ef,64}: Wrap -mno-branch-likely with cc-option

[Thomas Bogendoerfer]

On Tue, Jan 25, 2022 at 03:19:25PM -0700, Nathan Chancellor wrote:
> This flag is not supported by clang, which results in a warning:
> 
>   clang-14: warning: argument unused during compilation: '-mno-branch-likely' [-Wunused-command-line-argument]
> 
> This breaks cc-option, which adds -Werror to make this warning fatal and
> catch flags that are not supported.
> 
> Wrap this flag in cc-option so that it does not cause cc-option to fail,
> which can cause randconfigs to be really noisy, due to warnings not
> getting disabled that should be.
> 
> Additionally, move the cc-option check to Kconfig so that the check is
> done at configuration time, rather than build time, as builds with no
> configuration change will be quicker because the cc-option call will not
> need to happen in those instances.
> 
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
> 
> v1 -> v2: https://lore.kernel.org/r/20220120214001.1879469-2-nathan@kernel.org/
> 
> * Move cc-option call to Kconfig (Nick).
> * Also apply to loongson2ef, even though this will not currently build
>   with clang.
> 
>  arch/mips/Kconfig              | 4 ++++
>  arch/mips/loongson2ef/Platform | 3 ++-
>  arch/mips/loongson64/Platform  | 3 ++-
>  3 files changed, 8 insertions(+), 2 deletions(-)

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]