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

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Date:   Tue, 25 Jan 2022 15:19:24 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Huacai Chen <chenhuacai@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH v2 1/2] MIPS: Loongson64: Clean up use of cc-ifversion

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@...goat.com>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.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