[PATCH 3/6] aarch64: use an enumeration for operand indices.

[Alice Carlotti]

On Fri, Jul 18, 2025 at 11:03:58AM +0100, Richard Earnshaw wrote:
> The generated aarch64 operand tables use index values into an array.  But if
> the table of operands is modified by inserting a new operand into the middle
> of the table, *all* the index values can change, leading to a lot of
> churn in the generated output.
> 
> include/opcode/aarch64.h already provides an enumeration for the operands,
> so make use of that instead of printing out the raw index values.
> ---
>  opcodes/aarch64-gen.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/opcodes/aarch64-gen.c b/opcodes/aarch64-gen.c
> index ba48f06024e..17fca2fe4d5 100644
> --- a/opcodes/aarch64-gen.c
> +++ b/opcodes/aarch64-gen.c
> @@ -1027,8 +1027,9 @@ print_operand_table (void)
>    printf ("};\n");
>  }
>  
> -/* Generate aarch64_insert_operand in C to the standard output.  */
> +#define OPN_PFX_ENUM "AARCH64_OPND_"

I don't think this define improves clarity, and there are so many existing uses
of the enum names that it doesn't make it any easier to rename either.  So I'd
favour inlining this value into each use.

LGTM with that change.

>  
> +/* Generate aarch64_insert_operand in C to the standard output.  */
>  static void
>  print_operand_inserter (void)
>  {
> @@ -1047,7 +1048,7 @@ print_operand_inserter (void)
>  			   aarch64_operand_error *errors)\n");
>    printf ("{\n");
>    printf ("  /* Use the index as the key.  */\n");
> -  printf ("  int key = self - aarch64_operands;\n");
> +  printf ("  enum aarch64_opnd key = self - aarch64_operands;\n");
>    printf ("  switch (key)\n");
>    printf ("    {\n");
>  
> @@ -1061,7 +1062,7 @@ print_operand_inserter (void)
>  	  int j = i + 1;
>  	  const int len = strlen (opnd->inserter);
>  	  operand *opnd2 = opnd + 1;
> -	  printf ("    case %u:\n", (unsigned int)(opnd - operands));
> +	  printf ("    case " OPN_PFX_ENUM "%s:\n", opnd->str);
>  	  opnd->processed = 1;
>  	  for (; j < num; ++j, ++opnd2)
>  	    {
> @@ -1070,7 +1071,8 @@ print_operand_inserter (void)
>  		  && len == strlen (opnd2->inserter)
>  		  && strncmp (opnd->inserter, opnd2->inserter, len) == 0)
>  		{
> -		  printf ("    case %u:\n", (unsigned int)(opnd2 - operands));
> +		  printf ("    case " OPN_PFX_ENUM "%s:\n", opnd2->str);
> +
>  		  opnd2->processed = 1;
>  		}
>  	    }
> @@ -1104,7 +1106,7 @@ print_operand_extractor (void)
>  			   aarch64_operand_error *errors)\n");
>    printf ("{\n");
>    printf ("  /* Use the index as the key.  */\n");
> -  printf ("  int key = self - aarch64_operands;\n");
> +  printf ("  enum aarch64_opnd key = self - aarch64_operands;\n");
>    printf ("  switch (key)\n");
>    printf ("    {\n");
>  
> @@ -1118,7 +1120,7 @@ print_operand_extractor (void)
>  	  int j = i + 1;
>  	  const int len = strlen (opnd->extractor);
>  	  operand *opnd2 = opnd + 1;
> -	  printf ("    case %u:\n", (unsigned int)(opnd - operands));
> +	  printf ("    case " OPN_PFX_ENUM "%s:\n", opnd->str);
>  	  opnd->processed = 1;
>  	  for (; j < num; ++j, ++opnd2)
>  	    {
> @@ -1127,7 +1129,7 @@ print_operand_extractor (void)
>  		  && len == strlen (opnd2->extractor)
>  		  && strncmp (opnd->extractor, opnd2->extractor, len) == 0)
>  		{
> -		  printf ("    case %u:\n", (unsigned int)(opnd2 - operands));
> +		  printf ("    case " OPN_PFX_ENUM "%s:\n", opnd2->str);
>  		  opnd2->processed = 1;
>  		}
>  	    }
> -- 
> 2.43.0
>