In message <[EMAIL PROTECTED]> you wrote
:
>
> On Jun 18, 2008, at 11:35 PM, Michael Neuling wrote:
>
> > In message <5AEB0769-1394-4924-803D-
> > [EMAIL PROTECTED]> you wrote
> > :
> >>>
> >>>
> >>> Index: linux-2.6-ozlabs/include/asm-powerpc/processor.h
> >>> ===================================================================
> >>> --- linux-2.6-ozlabs.orig/include/asm-powerpc/processor.h
> >>> +++ linux-2.6-ozlabs/include/asm-powerpc/processor.h
> >>> @@ -78,6 +78,7 @@ extern long kernel_thread(int (*fn)(void
> >>> /* Lazy FPU handling on uni-processor */
> >>> extern struct task_struct *last_task_used_math;
> >>> extern struct task_struct *last_task_used_altivec;
> >>> +extern struct task_struct *last_task_used_vsx;
> >>> extern struct task_struct *last_task_used_spe;
> >>>
> >>> #ifdef CONFIG_PPC32
> >>> @@ -136,8 +137,13 @@ typedef struct {
> >>> unsigned long seg;
> >>> } mm_segment_t;
> >>>
> >>> +#ifdef CONFIG_VSX
> >>> +#define TS_FPR(i) fpvsr.fp[i].fpr
> >>> +#define TS_FPRSTART fpvsr.fp
> >>> +#else
> >>> #define TS_FPR(i) fpr[i]
> >>> #define TS_FPRSTART fpr
> >>> +#endif
> >>>
> >>> struct thread_struct {
> >>> unsigned long ksp; /* Kernel stack pointer */
> >>> @@ -155,8 +161,19 @@ struct thread_struct {
> >>> unsigned long dbcr0; /* debug control register values */
> >>> unsigned long dbcr1;
> >>> #endif
> >>> +#ifdef CONFIG_VSX
> >>> + /* First 32 VSX registers (overlap with fpr[32]) */
> >>> + union {
> >>> + struct {
> >>> + double fpr;
> >>> + double vsrlow;
> >>> + } fp[32];
> >>> + vector128 vsr[32];
>
> how about:
>
> union {
> struct {
> double fp;
> double vsrlow;
> } fpr;
> vector128 v;
> } fpvsr[32];
Arrh, yep, makes more sense to put the array definition outside the
union. I'll change.
>
> >>>
> >>> + } fpvsr __attribute__((aligned(16)));
> >>
> >> Do we really need a union here? what would happen if you just
> >> changed
> >> the type of fpr[32] from double to vector if #CONFIG_VSX?
> >>
> >> I really dont like the union and think we can just make the storage
> >> look opaque which is the key. I doubt we every really care about
> >> using fpr[] as a double in the kernel.
> >
> > I did something similar to this for the first cut of this patch, but
> > it
> > made the code accessing this structure much less readable.
>
> really, what code is that?
Any code that has to read/write the top or bottom 64 bits _only_ of the
128 bit vector.
The signals code is a good example where, for backwards compatibility,
we need to read/write the old 64 bit FP regs, from the 128 bit value in
the struct.
Similarly, the way we've extended the signals interface for VSX, you
need to read/write out the bottom 64 bits (vsrlow) of a 128 bit value.
eg. the simple:
current->thread.fpvsr.fp[i].vsrlow = buf[i]
would turn into some abomination/macro.
Mikey
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