[DTrace-devel] [PATCH v2 1/3] Rename "path" helper to "tstring1" helper

[Eugene Loh]

R-b with the proposed changes?

On 4/19/22 11:32 PM, Kris Van Hees wrote:
> On Fri, Mar 18, 2022 at 03:36:42PM -0400, eugene.loh--- via DTrace-devel wrote:
>> From: Eugene Loh <eugene.loh at oracle.com>
>>
>> When the code generator sets up a call to a precompiled BPF function,
>> it emits a lot of boilerplate code.  The implementations of DTrace
>> subroutines typically make such calls.  So there is potential for
>> much code reuse.
>>
>> The "path" helper is one such attempt.  Since its usefulness is
>> broader than just for a "path name" argument, rename this helper to
>> suggest its broader usage more clearly.
>>
>> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
>> ---
>>   libdtrace/dt_cg.c | 39 +++++++++++++++++++++------------------
>>   1 file changed, 21 insertions(+), 18 deletions(-)
>>
>> diff --git a/libdtrace/dt_cg.c b/libdtrace/dt_cg.c
>> index c40fef41..b8325e44 100644
>> --- a/libdtrace/dt_cg.c
>> +++ b/libdtrace/dt_cg.c
>> @@ -3316,24 +3316,27 @@ dt_cg_array_op(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
>>   }
>>   
>>   /*
>> - * This function is a helper function for subroutines that take a path
>> - * argument and return the tstring resulting from applying a given BPF
>> - * function (passed by name) on it.
>> + * This helper emits code to call a precompiled BPF function (named
>> + * by fname) that is of return type void and takes two arguments:
>> + *   - one input value
>> + *   - a pointer to an output tstring, allocated here
>>    */
>>   static void
>> -dt_cg_subr_path_helper(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
>> -		       const char *fname)
>> +dt_cg_subr_tstring1_helper(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
>> +			   const char *fname)
> s/dt_cg_subr_tstring1_helper/dt_cg_subr_arg_to_tstring/
>
>>   {
>>   	dt_ident_t	*idp;
>> -	dt_node_t	*str = dnp->dn_args;
>> +	dt_node_t	*arg = dnp->dn_args;
>>   
>> -	TRACE_REGSET("    subr-path_helper:Begin");
>> -	dt_cg_node(str, dlp, drp);
>> -	dt_cg_check_notnull(dlp, drp, str->dn_reg);
>> +	TRACE_REGSET("    subr-tstring1_helper:Begin");
> s/subr-tstring1_helper/subr-arg-to-tstring/
>
>>   
>> -	/*
>> -	 * The result needs be be a temporary string, so we request one.
>> -	 */
>> +	/* handle the one "input value" */
>> +	/* (its type matters only as to whether we check it is null */
>> +	dt_cg_node(arg, dlp, drp);
>> +	if (dt_node_is_pointer(arg) || dt_node_is_string(arg))
>> +		dt_cg_check_notnull(dlp, drp, arg->dn_reg);
> This should be changed to support alloca pointers:
>
> 	if (dt_node_is_pointer(arg) || dt_node_is_string(arg))
> 		dt_cg_check_ptr_arg(dlp, drp, arg);
>
>> +
>> +	/* allocate the temporary string */
>>   	dnp->dn_reg = dt_regset_alloc(drp);
>>   	if (dnp->dn_reg == -1)
>>   		longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
>> @@ -3346,9 +3349,9 @@ dt_cg_subr_path_helper(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
>>   	if (dt_regset_xalloc_args(drp) == -1)
>>   		longjmp(yypcb->pcb_jmpbuf, EDT_NOREG);
>>   
>> -	emit(dlp, BPF_MOV_REG(BPF_REG_1, str->dn_reg));
>> -	dt_regset_free(drp, str->dn_reg);
>> -	dt_cg_tstring_free(yypcb, str);
>> +	emit(dlp, BPF_MOV_REG(BPF_REG_1, arg->dn_reg));
>> +	dt_regset_free(drp, arg->dn_reg);
>> +	dt_cg_tstring_free(yypcb, arg);
> How about:
>
> 	if (dt_node_is_string(arg))
> 		dt_cg_tstring_free(yypcb, arg);
>
>>   
>>   	emit(dlp,  BPF_MOV_REG(BPF_REG_2, dnp->dn_reg));
>>   
>> @@ -3359,19 +3362,19 @@ dt_cg_subr_path_helper(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp,
>>   	dt_regset_free_args(drp);
>>   	dt_regset_free(drp, BPF_REG_0);
>>   
>> -	TRACE_REGSET("    subr-path_helper:End  ");
>> +	TRACE_REGSET("    subr-tstring1_helper:End  ");
>>   }
>>   
>>   static void
>>   dt_cg_subr_basename(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
>>   {
>> -	dt_cg_subr_path_helper(dnp, dlp, drp, "dt_basename");
>> +	dt_cg_subr_tstring1_helper(dnp, dlp, drp, "dt_basename");
>>   }
>>   
>>   static void
>>   dt_cg_subr_dirname(dt_node_t *dnp, dt_irlist_t *dlp, dt_regset_t *drp)
>>   {
>> -	dt_cg_subr_path_helper(dnp, dlp, drp, "dt_dirname");
>> +	dt_cg_subr_tstring1_helper(dnp, dlp, drp, "dt_dirname");
>>   }
>>   
>>   /*
>> -- 
>> 2.18.4
>>
>>
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