[DTrace-devel] [PATCH 4/6 v2] Add macro to access stack slots past the register spill area

[Eugene Loh]

Encore:
Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
with two tiny things:

On 3/11/22 1:26 AM, Kris Van Hees via DTrace-devel wrote:
> The DT_TRAMP_SP9n) macro has been renamed to DT_TRAMP_SP_SLOT(n) for
s/9n)/(n)/
> consistency with the new DT_STK_SP_SLOT(n) macro.  DT_STK_SP is new
> and refers to the location of a "stack pointer" that holds the address
> of a DT_STK_SP_SLOT.
>
> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> Reviewed-by: Eugene Loh <eugene.loh at oracle.com
> diff --git a/libdtrace/dt_dctx.h b/libdtrace/dt_dctx.h
> @@ -142,24 +142,29 @@ typedef struct dt_dctx {
>    *       -16, -24, -32, etc. -- that is, negative multiples of sizeof(uint64_t).
>    *
>    *                       +----------------+
> - *          SCRATCH_BASE | Scratch Memory |
> - *                       +----------------+
> - *              SPILL(n) | %r8            | (n = DT_STK_NREGS - 1 = 8)
> - *                       +----------------+
>    *                       |      ...       |
>    *                       +----------------+
> - *              SPILL(1) | %r1            |
> - *                       +----------------+
> - * SPILL_BASE = SPILL(0) | %r0            |
> + *  SP_BASE = SP_SLOT(0) |                |<--+
> + *                       +----------------+   |
> + *              SPILL(n) | %r8            | (n = DT_STK_NREGS - 1 = 8)
> + *                       +----------------+   |
> + *                       |      ...       |   |
> + *                       +----------------+   |
> + *              SPILL(1) | %r1            |   |
> + *                       +----------------+   |
> + * SPILL_BASE = SPILL(0) | %r0            |   |
> + *                       +----------------+   |
> + *                    SP |       +------------+ (initial value)

Instead of +------ for the tail of the arrow, how about >>>-----, which 
is more suggestive of the fletchings of an arrow.  Having the tail 
marked with a '+' is confusing since that char means something else in 
this diagram.

>    *                       +----------------+
>    *                  DCTX | Ptr to dctx    |
>    *                       +----------------+
>    */