[DTrace-devel] [PATCH 32/61] Add dt_cg_push_stack()

[Kris Van Hees]

Let's defer this and add it to the patch that introduces dt_cg_pop_stack()
as well.  That (I think) makes more sense, and in the meantime the existing
code can just remain.  I was planning on introducing such functions down the
road anyway as part of the spill/fill rewrite but since you have a use for
it now, let's do it with the other patch:

	"Add support for aggregation keys"

On Fri, Jul 08, 2022 at 10:45:16AM -0400, eugene.loh--- via DTrace-devel wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> This patch prepares for future, additional uses of this stack.
> 
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
> ---
>  libdtrace/dt_cg.c | 26 +++++++++++++++++---------
>  1 file changed, 17 insertions(+), 9 deletions(-)
> 
> diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
> index 11a9c8c5..b0c2a362 100644
> --- a/libdtrace/dt_cg.c
> +++ b/libdtrace/dt_cg.c
> @@ -2607,6 +2607,22 @@ dt_cg_typecast(const dt_node_t *src, const dt_node_t *dst,
>  	}
>  }
>  
> +static void
> +dt_cg_push_stack(dt_irlist_t *dlp, dt_regset_t *drp, int reg)
> +{
> +	int tmp;
> +
> +	if ((tmp = dt_regset_alloc(drp)) == -1)
> +		longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
> +
> +	emit(dlp, BPF_LOAD(BPF_DW, tmp, BPF_REG_FP, DT_STK_SP));
> +	emit(dlp, BPF_STORE(BPF_DW, tmp, 0, reg));
> +	dt_regset_free(drp, reg);
> +	emit(dlp, BPF_ALU64_IMM(BPF_ADD, tmp, -DT_STK_SLOT_SZ));
> +	emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DT_STK_SP, tmp));
> +	dt_regset_free(drp, tmp);
> +}
> +
>  /*
>   * Generate code to push the specified argument list on to the tuple stack.
>   * We use this routine for handling the index tuple for associative arrays.
> @@ -2644,15 +2660,7 @@ dt_cg_arglist(dt_ident_t *idp, dt_node_t *args, dt_irlist_t *dlp,
>  			longjmp(yypcb->pcb_jmpbuf, EDT_NOTUPREG);
>  
>  		dt_cg_node(dnp, dlp, drp);
> -
> -		/* Push the component (pointer or value) onto the stack. */
> -		dt_regset_xalloc(drp, BPF_REG_0);
> -		emit(dlp, BPF_LOAD(BPF_DW, BPF_REG_0, BPF_REG_FP, DT_STK_SP));
> -		emit(dlp, BPF_STORE(BPF_DW, BPF_REG_0, 0, dnp->dn_reg));
> -		dt_regset_free(drp, dnp->dn_reg);
> -		emit(dlp, BPF_ALU64_IMM(BPF_ADD, BPF_REG_0, -DT_STK_SLOT_SZ));
> -		emit(dlp, BPF_STORE(BPF_DW, BPF_REG_FP, DT_STK_SP, BPF_REG_0));
> -		dt_regset_free(drp, BPF_REG_0);
> +		dt_cg_push_stack(dlp, drp, dnp->dn_reg);
>  	}
>  
>  	TRACE_REGSET("      arglist: Stack");
> -- 
> 2.18.4
> 
> 
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