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Re: [Minios-devel] [UNIKRAFT PATCH] Add support for clang compilation
Hi Simon,
Sounds good to me. Thank you very much for advices, I took them into account and implemented them.
Thanks, Alice
Hi Alice,
thanks a lot for this work! It will (unfortunately) need a some rtework
because we had recently changes on how build flags are propagated.
On 01.03.20 20:13, alicesuiu wrote:
> Remove some flags (-fno-tree-sra, -mno-fp-ret-in-387, -fno-reorder-blocks) to add support for clang compilation.
> Add the CONFIG_COMPILER variable to define the compiler to be used (gcc or clang). By default the variable is set to gcc.
> Use 'make COMPILER=clang' to compile with clang.
>
> Signed-off-by: Alice Suiu <alicesuiu17@xxxxxxxxx>
> ---
> Makefile | 12 ++++++++++--
> Makefile.uk | 6 +++---
> arch/x86/x86_64/Makefile.uk | 6 +++---
> 3 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 84adb16..5828891 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -481,11 +481,19 @@ ifneq ("$(origin CROSS_COMPILE)","undefined")
> CONFIG_CROSS_COMPILE := $(CROSS_COMPILE:"%"=%)
> endif
>
> +# Use 'make COMPILER=clang' to compile with clang
> +ifeq ("$(origin COMPILER)", "command line")
> + CONFIG_COMPILER := $(COMPILER)
> +endif
> +ifndef CONFIG_COMPILER
> + CONFIG_COMPILER = gcc
> +endif
> +
> include $(CONFIG_UK_BASE)/arch/$(UK_FAMILY)/Compiler.uk
>
> # Make variables (CC, etc...)
> -LD := $(CONFIG_CROSS_COMPILE)gcc
> -CC := $(CONFIG_CROSS_COMPILE)gcc
> +LD := $(CONFIG_CROSS_COMPILE)$(CONFIG_COMPILER)
> +CC := $(CONFIG_CROSS_COMPILE)$(CONFIG_COMPILER)
> CPP := $(CC)
> CXX := $(CPP)
> GOC := $(CONFIG_CROSS_COMPILE)gccgo-7
I guess Go can also compiled with clang? It is fine to add support
later, I am asking out of curiosity.
> diff --git a/Makefile.uk b/Makefile.uk
> index 3f01a25..3890d62 100644
> --- a/Makefile.uk
> +++ b/Makefile.uk
> @@ -8,17 +8,17 @@ ASFLAGS += -U __linux__ -U __FreeBSD__ -U __sun__ -D__ASSEMBLY__
> ASINCLUDES += -nostdinc -nostdlib -I$(CONFIG_UK_BASE)/include
>
> CFLAGS += -U __linux__ -U __FreeBSD__ -U __sun__
> -CFLAGS += -fno-stack-protector -fno-omit-frame-pointer -fno-tree-sra
> +CFLAGS += -fno-stack-protector -fno-omit-frame-pointer
> CFLAGS += -Wall -Wextra
> CINCLUDES += -nostdinc -nostdlib -I$(CONFIG_UK_BASE)/include
>
> CXXFLAGS += -U __linux__ -U __FreeBSD__ -U __sun__
> -CXXFLAGS += -fno-stack-protector -fno-omit-frame-pointer -fno-tree-sra
> +CXXFLAGS += -fno-stack-protector -fno-omit-frame-pointer
> CXXFLAGS += -Wall -Wextra
> CXXINCLUDES += -nostdinc -nostdlib -I$(CONFIG_UK_BASE)/include
>
> GOCFLAGS += -U __linux__ -U __FreeBSD__ -U __sun__
> -GOCFLAGS += -fno-stack-protector -fno-omit-frame-pointer -fno-tree-sra
> +GOCFLAGS += -fno-stack-protector -fno-omit-frame-pointer
> GOCFLAGS += -fno-split-stack -Wall -Wextra
> GOCINCLUDES += -nostdinc -nostdlib -I$(CONFIG_UK_BASE)/include
Please note that all language-independent flags moved to:
ARCHFLAGS, ISR_ARCHFLAGS, COMPFLAGS
>
> diff --git a/arch/x86/x86_64/Makefile.uk b/arch/x86/x86_64/Makefile.uk
> index 8ec7d6b..285a4e9 100644
> --- a/arch/x86/x86_64/Makefile.uk
> +++ b/arch/x86/x86_64/Makefile.uk
> @@ -1,9 +1,9 @@
> ASFLAGS += -D__X86_64__
> ASFLAGS += -m64
> CFLAGS += -D__X86_64__
> -CFLAGS += -m64 -mno-red-zone -fno-reorder-blocks -fno-asynchronous-unwind-tables
> +CFLAGS += -m64 -mno-red-zone -fno-asynchronous-unwind-tables
> CXXFLAGS += -D__X86_64__
> -CXXFLAGS += -m64 -mno-red-zone -fno-reorder-blocks -fno-asynchronous-unwind-tables
> +CXXFLAGS += -m64 -mno-red-zone -fno-asynchronous-unwind-tables
>
Also those, while we still have the language-specific flags (ASFLAGS,
CFLAGS, etc.). We separate them now.
> CINCLUDES += -I$(CONFIG_UK_BASE)/arch/x86/x86_64/include
> ASINCLUDES += -I$(CONFIG_UK_BASE)/arch/x86/x86_64/include
> @@ -11,7 +11,7 @@ CXXINCLUDES += -I$(CONFIG_UK_BASE)/arch/x86/x86_64/include
>
> # compiler flags to prevent use of extended (FP, SSE, AVX) registers.
> # This is for files that contain trap/exception/interrupt handlers
> -NO_X86_EXTREGS_FLAGS := -mno-80387 -mno-fp-ret-in-387 -mno-mmx -mno-sse -mno-avx
> +NO_X86_EXTREGS_FLAGS := -mno-80387 -mno-mmx -mno-sse -mno-avx
>
> ASFLAGS-$(CONFIG_MARCH_X86_64_GENERIC) += -mtune=generic
> CFLAGS-$(CONFIG_MARCH_X86_64_GENERIC) += -mtune=generic
>
I think we should add and modify the compiler-related Makefile rules
within `support/build/Makefile.rules`. We have there so far:
gcc_version_ge returns 'y' if current GCC version is >= 'y',
otherwise 'n'
gcc_version_lt returns 'y' if current GCC version is < 'y',
otherwise 'n'
These two are used to populate flags according to the current used GCC
version. For instance:
COMPFLAGS-$(call gcc_version_ge,7,0) += -flag_supported_with_gcc70
error_if_gcc_version_lt Will output an error that a newer GCC
is needed
I think I would add two functions that return 'y' and 'n' when clang and
GCC is detected:
have_clang
have_gcc
Using those, it probably makes sense to update the three existing
functions so that the first two return 'n' and the last one never fails
when have_gcc returned 'n' (when clang is used). Additionally, I would
add the same set of functions for clang:
clang_version_ge
clang_version_le
error_if_clang_version_lt
They behave equivalently to the gcc functions so that nothing breaks
when GCC is used instead of clang (have_clang).
With all of this you are able to re-coordinate the flags. All flags that
fail with clang, you would keep for GCC with
COMPFLAGS-$(call have_gcc) += -gcc_only_flag
With this you can also introduce clang specific flags and it can be
applied to all flag variables, including the language specific ones and
the ones concerning linking.
What do you think?
Thanks,
Simon
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