Re: [AArch64] fix big.LITTLE spec rewriting

[James Greenhalgh <james dot greenhalgh at arm dot com>]

*ping*

On Tue, Jan 21, 2014 at 10:48:04AM +0000, James Greenhalgh wrote:
> 
> Hi,
> 
> As Charles Baylis pointed out here:
> 
> http://gcc.gnu.org/ml/gcc-patches/2014-01/msg00921.html
> 
> The way that we rewrite command lines for big.LITTLE systems
> causes bugs where more than one source file is to be used.
> The problem fundamentally is that -mcpu never makes it to
> the second cc1 invocation.
> 
> This patch changes the spec command we use and updates
> aarch64-common.c to handle that fact. I confess that the specs
> stuff all looks like magic to me, but this approach seems to
> make sense. In English, I think I am saying:
> 
> "If you find an mcpu= followed by some name, rewrite that to be
>  -mcpu followed by the results of passing all other -mcpu values
>  we find through aarch64_rewrite_mcpu"
> 
> I've regression tested this patch on aarch64-none-elf with no
> issues and checked combinations of zero or more -mcpu values with
> one or more source files, and things seem to work as expected.
> 
> OK?
> 
> Thanks,
> James
> 
> ---
> 2014-01-21  James Greenhalgh  <james.greenhalgh@arm.com>
> 
> 	* common/config/aarch64/aarch64-common.c
> 	(aarch64_rewrite_mcpu): Handle multiple names.
> 	* config/aarch64/aarch64.h
> 	(BIG_LITTLE_SPEC): Do not discard mcpu switches.
> 

> diff --git a/gcc/common/config/aarch64/aarch64-common.c b/gcc/common/config/aarch64/aarch64-common.c
> index 6107007..e44b40a 100644
> --- a/gcc/common/config/aarch64/aarch64-common.c
> +++ b/gcc/common/config/aarch64/aarch64-common.c
> @@ -110,13 +110,15 @@ aarch64_rewrite_selected_cpu (const char *name)
>  
>  /* Called by the driver to rewrite a name passed to the -mcpu
>     argument in preparation to be passed to the assembler.  The
> -   name will be in ARGV[0], ARGC should always be 1.  */
> +   names passed from the commend line will be in ARGV, we want
> +   to use the right-most argument, which should be in
> +   ARGV[ARGC - 1].  ARGC should always be greater than 0.  */
>  
>  const char *
>  aarch64_rewrite_mcpu (int argc, const char **argv)
>  {
> -  gcc_assert (argc == 1);
> -  return aarch64_rewrite_selected_cpu (argv[0]);
> +  gcc_assert (argc);
> +  return aarch64_rewrite_selected_cpu (argv[argc - 1]);
>  }
>  
>  #undef AARCH64_CPU_NAME_LENGTH
> diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
> index a08dee0..13c424c 100644
> --- a/gcc/config/aarch64/aarch64.h
> +++ b/gcc/config/aarch64/aarch64.h
> @@ -857,7 +857,7 @@ extern enum aarch64_code_model aarch64_cmodel;
>    (BYTES_BIG_ENDIAN ? GET_MODE_NUNITS (mode) - 1 - n : n)
>  
>  #define BIG_LITTLE_SPEC \
> -   " %{mcpu=*:%<mcpu=* -mcpu=%:rewrite_mcpu(%{mcpu=*:%*})}"
> +   " %{mcpu=*:-mcpu=%:rewrite_mcpu(%{mcpu=*:%*})}"
>  
>  extern const char *aarch64_rewrite_mcpu (int argc, const char **argv);
>  #define BIG_LITTLE_CPU_SPEC_FUNCTIONS \