Re: [PATCH, rs6000] Add non-relative jump table support on Power Linux

[Segher Boessenkool <segher@kernel.crashing.org>]

Hi hao Chen,

On Wed, Sep 09, 2020 at 04:55:29PM +0800, HAO CHEN GUI wrote:
>     Thanks for your advice. I removed macros defined in linux64.h and 
> linux.h. So they take relative jump tables by default. When 
> no-relative-jumptables is set, the absolute jump tables are taken. All 
> things relevant to section relocations are put in another patch. Thanks 
> again.

[ Please do not insert patches into discussions ]

> +/* Implement TARGET_ASM_GENERATE_PIC_ADDR_DIFF_VEC.
> +   Return true if rs6000_relative_jumptables is set.  */

Don't just say what the code does (we can see that ;-) ); say *why*.
Of course it is terribly simple in this case, so maybe just that first
line is plenty.

> +/* Specify the machine mode that this machine uses
> +   for the index in the tablejump instruction.  */
> +#define CASE_VECTOR_MODE \
> +  (TARGET_32BIT || rs6000_relative_jumptables ? SImode : Pmode)

If TARGET_32BIT is true, SImode and Pmode are the same, so this is
simpler said as

#define CASE_VECTOR_MODE (rs6000_relative_jumptables ? SImode : Pmode)


I'll have the tablejump* patterns converted to paremeterized names
hopefully tonight or tomorrow, which will make your patch much easier
to read.  It looks like it will be fine, thanks :-)


Segher