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sparc/build: Put usage of -fcall-used* flags behind cc-option

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Place -fcall-used* flags behind cc-option so that clang (which doesn't
support them) can still compile the kernel.

This is a safe change, the reasoning is as follows:

In the (normal) 32-bit ABI, %g5 and %g7 is normally reserved, and in
the 64-bit ABI, %g7 is the reserved one.
Linux turns them into volatile registers by the way of -fcall-used-*,
but on the other hand, omitting the flags shouldn't be harmful;
compilers will now simply refuse to touch them, and any assembly
code that happens to touch them would still work like usual (because
Linux' conventions already treats them as volatile anyway).

Signed-off-by: Koakuma <koachan@protonmail.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Andreas Larsson <andreas@gaisler.com>
Link: https://lore.kernel.org/r/20241029-sparc-cflags-v3-1-b28745a6bd71@protonmail.com
Signed-off-by: Andreas Larsson <andreas@gaisler.com>
This commit is contained in:
Koakuma 2024-10-29 21:49:07 +07:00 committed by Andreas Larsson
parent 9852d85ec9
commit 69114be15b
2 changed files with 3 additions and 3 deletions
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4
arch/sparc/Makefile
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@ -29,7 +29,7 @@ UTS_MACHINE := sparc
# versions of gcc. Some gcc versions won't pass -Av8 to binutils when you
# give -mcpu=v8. This silently worked with older bintutils versions but
# does not any more.
KBUILD_CFLAGS += -m32 -mcpu=v8 -pipe -mno-fpu -fcall-used-g5 -fcall-used-g7
KBUILD_CFLAGS += -m32 -mcpu=v8 -pipe -mno-fpu $(call cc-option,-fcall-used-g5) $(call cc-option,-fcall-used-g7)
KBUILD_CFLAGS += -Wa,-Av8
KBUILD_AFLAGS += -m32 -Wa,-Av8
@ -45,7 +45,7 @@ export BITS := 64
UTS_MACHINE := sparc64
KBUILD_CFLAGS += -m64 -pipe -mno-fpu -mcpu=ultrasparc -mcmodel=medlow
KBUILD_CFLAGS += -ffixed-g4 -ffixed-g5 -fcall-used-g7 -Wno-sign-compare
KBUILD_CFLAGS += -ffixed-g4 -ffixed-g5 $(call cc-option,-fcall-used-g7) -Wno-sign-compare
KBUILD_CFLAGS += -Wa,--undeclared-regs
KBUILD_CFLAGS += $(call cc-option,-mtune=ultrasparc3)
KBUILD_AFLAGS += -m64 -mcpu=ultrasparc -Wa,--undeclared-regs

2
arch/sparc/vdso/Makefile
View File

@ -46,7 +46,7 @@ CFL := $(PROFILING) -mcmodel=medlow -fPIC -O2 -fasynchronous-unwind-tables -m64
-fno-omit-frame-pointer -foptimize-sibling-calls \
-DDISABLE_BRANCH_PROFILING -DBUILD_VDSO
SPARC_REG_CFLAGS = -ffixed-g4 -ffixed-g5 -fcall-used-g5 -fcall-used-g7
SPARC_REG_CFLAGS = -ffixed-g4 -ffixed-g5 $(call cc-option,-fcall-used-g5) $(call cc-option,-fcall-used-g7)
$(vobjs): KBUILD_CFLAGS := $(filter-out $(RANDSTRUCT_CFLAGS) $(GCC_PLUGINS_CFLAGS) $(SPARC_REG_CFLAGS),$(KBUILD_CFLAGS)) $(CFL)