Re: [Xen-devel] [PATCH 8 of 8] xen: add "clang=y" option to build Xen with clang/llvm instead of gcc

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2011-03-07 at 11:26 +0000, Tim Deegan wrote:
> # HG changeset patch
> # User Tim Deegan <Tim.Deegan@xxxxxxxxxx>
> # Date 1299496871 0
> # Node ID d91e6a8d36ad3dbf89f42264334baec0cb37063f
> # Parent  804007170cf03ea832022e2d589507a3bc0505dc
> xen: add "clang=y" option to build Xen with clang/llvm instead of gcc.
> 
> Tested with svn snapshot of clang and llvm from 17 February 2011.
> Only x86_64 hypervisor builds (make dist-xen clang=y) are supported
> and I haven't even begun to look at cross-compiling.
> 
> Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
> 
> diff -r 804007170cf0 -r d91e6a8d36ad Config.mk
> --- a/Config.mk Mon Mar 07 11:21:11 2011 +0000
> +++ b/Config.mk Mon Mar 07 11:21:11 2011 +0000
> @@ -148,6 +148,13 @@ CFLAGS += -Wall -Wstrict-prototypes
>  # result of any casted expression causes a warning.
>  CFLAGS += -Wno-unused-value
>  
> +ifeq ($(clang),y)
> +# Clang complains about macros that expand to 'if ( ( foo == bar )
> ) ...'
> +CFLAGS += -Wno-parentheses
> +# And is over-zealous with the printf format lint
> +CFLAGS += -Wno-format
> +endif

Is it worth arranging for "gcc := y" when clang is not enabled? Then a
whole bunch of this sort of thing devolves into the 
        CFLAGS-$(a-particular-cc) += -Wfoo
pattern.

> +
>  $(call cc-option-add,HOSTCFLAGS,HOSTCC,-Wdeclaration-after-statement)
>  $(call cc-option-add,CFLAGS,CC,-Wdeclaration-after-statement)
>  
> diff -r 804007170cf0 -r d91e6a8d36ad config/StdGNU.mk
> --- a/config/StdGNU.mk  Mon Mar 07 11:21:11 2011 +0000
> +++ b/config/StdGNU.mk  Mon Mar 07 11:21:11 2011 +0000
> @@ -1,6 +1,11 @@
>  AS         = $(CROSS_COMPILE)as
> +ifeq ($(clang),y)
> +LD         = $(CROSS_COMPILE)gold
> +CC         = $(CROSS_COMPILE)clang
> +else
>  LD         = $(CROSS_COMPILE)ld
>  CC         = $(CROSS_COMPILE)gcc
> +endif
>  CPP        = $(CC) -E
>  AR         = $(CROSS_COMPILE)ar
>  RANLIB     = $(CROSS_COMPILE)ranlib

LD-$(clang) = ...
LD-$(gcc)   = ...

LD := $(LD-y)

?

> @@ -69,5 +74,8 @@ ifneq ($(debug),y)
>  CFLAGS += -O2 -fomit-frame-pointer
>  else
>  # Less than -O1 produces bad code and large stack frames
> -CFLAGS += -O1 -fno-omit-frame-pointer -fno-optimize-sibling-calls
> +CFLAGS += -O1 -fno-omit-frame-pointer
> +ifneq ($(clang),y)
> +CFLAGS += -fno-optimize-sibling-calls

CFLAGS-$(gcc) += ...

etc etc

Ian.



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