Re: [Tarantool-patches] [PATCH luajit 09/19] FFI: Eliminate hardcoded string hashes.

[Sergey Bronnikov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

Hi, Sergey


Thanks for the patch! LGTM

On 8/15/23 16:07, Maxim Kokryashkin wrote:
> Hi, Sergey!
> Thanks for the patch!
> LGTM, except for a few comments below.
>
> On Wed, Aug 09, 2023 at 06:35:58PM +0300, Sergey Kaplun via Tarantool-patches wrote:
>> From: Mike Pall <mike>
>>
>> (cherry-picked from commit 70f4b15ee45a6137fe6b48b941faea79d72f7159)
>>
>> This patch refactors FFI parsing of supported C attributes and pragmas,
>> `ffi.abi()` parameter check. It replaces usage of comparison (with
> Typo: s/usage/the usage/
>> hardcoded string hashes) with search in the given string with the
> Typo: s/with search/with a search/
>> format: "\XXXattribute1\XXXattribute2", where `\XXX` is the length of
>> "attribute" name.
>>
>> Sergey Kaplun:
>> * added the description for the commit
>>
>> Part of tarantool/tarantool#8825
>> ---
>>   src/lib_ffi.c   | 35 ++++++++++------------
>>   src/lj_cparse.c | 77 +++++++++++++++++++++++++++++++------------------
>>   src/lj_cparse.h |  2 ++
>>   3 files changed, 67 insertions(+), 47 deletions(-)
>>
>> diff --git a/src/lib_ffi.c b/src/lib_ffi.c
>> index d1fe1a14..62af54c1 100644
>> --- a/src/lib_ffi.c
>> +++ b/src/lib_ffi.c
>> @@ -720,50 +720,47 @@ LJLIB_CF(ffi_fill)	LJLIB_REC(.)
>>     return 0;
>>   }
>>   
>> -#define H_(le, be)	LJ_ENDIAN_SELECT(0x##le, 0x##be)
>> -
>>   /* Test ABI string. */
>>   LJLIB_CF(ffi_abi)	LJLIB_REC(.)
>>   {
>>     GCstr *s = lj_lib_checkstr(L, 1);
>> -  int b = 0;
>> -  switch (s->hash) {
>> +  int b = lj_cparse_case(s,
>>   #if LJ_64
>> -  case H_(849858eb,ad35fd06): b = 1; break;  /* 64bit */
>> +    "\00564bit"
>>   #else
>> -  case H_(662d3c79,d0e22477): b = 1; break;  /* 32bit */
>> +    "\00532bit"
>>   #endif
>>   #if LJ_ARCH_HASFPU
>> -  case H_(e33ee463,e33ee463): b = 1; break;  /* fpu */
>> +    "\003fpu"
>>   #endif
>>   #if LJ_ABI_SOFTFP
>> -  case H_(61211a23,c2e8c81c): b = 1; break;  /* softfp */
>> +    "\006softfp"
>>   #else
>> -  case H_(539417a8,8ce0812f): b = 1; break;  /* hardfp */
>> +    "\006hardfp"
>>   #endif
>>   #if LJ_ABI_EABI
>> -  case H_(2182df8f,f2ed1152): b = 1; break;  /* eabi */
>> +    "\004eabi"
>>   #endif
>>   #if LJ_ABI_WIN
>> -  case H_(4ab624a8,4ab624a8): b = 1; break;  /* win */
>> +    "\003win"
>>   #endif
>>   #if LJ_TARGET_UWP
>> -  case H_(a40f0bcb,a40f0bcb): b = 1; break;  /* uwp */
>> +    "\003uwp"
>> +#endif
>> +#if LJ_LE
>> +    "\002le"
>> +#else
>> +    "\002be"
>>   #endif
>> -  case H_(3af93066,1f001464): b = 1; break;  /* le/be */
>>   #if LJ_GC64
>> -  case H_(9e89d2c9,13c83c92): b = 1; break;  /* gc64 */
>> +    "\004gc64"
>>   #endif
>> -  default:
>> -    break;
>> -  }
>> +  ) >= 0;
>>     setboolV(L->top-1, b);
>>     setboolV(&G(L)->tmptv2, b);  /* Remember for trace recorder. */
>>     return 1;
>>   }
>>   
>> -#undef H_
>> -
>>   LJLIB_PUSH(top-8) LJLIB_SET(!)  /* Store reference to miscmap table. */
>>   
>>   LJLIB_CF(ffi_metatype)
>> diff --git a/src/lj_cparse.c b/src/lj_cparse.c
>> index fb440567..07c643d4 100644
>> --- a/src/lj_cparse.c
>> +++ b/src/lj_cparse.c
>> @@ -28,6 +28,24 @@
>>   ** If in doubt, please check the input against your favorite C compiler.
>>   */
>>   
>> +/* -- Miscellaneous ------------------------------------------------------- */
>> +
>> +/* Match string against a C literal. */
>> +#define cp_str_is(str, k) \
>> +  ((str)->len == sizeof(k)-1 && !memcmp(strdata(str), k, sizeof(k)-1))
>> +
>> +/* Check string against a linear list of matches. */
>> +int lj_cparse_case(GCstr *str, const char *match)
>> +{
>> +  MSize len;
>> +  int n;
>> +  for  (n = 0; (len = (MSize)*match++); n++, match += len) {
>> +    if (str->len == len && !memcmp(match, strdata(str), len))
>> +      return n;
>> +  }
>> +  return -1;
>> +}
>> +
>>   /* -- C lexer ------------------------------------------------------------- */
>>   
>>   /* C lexer token names. */
>> @@ -930,8 +948,6 @@ static CTypeID cp_decl_intern(CPState *cp, CPDecl *decl)
>>   
>>   /* -- C declaration parser ------------------------------------------------ */
>>   
>> -#define H_(le, be)	LJ_ENDIAN_SELECT(0x##le, 0x##be)
>> -
>>   /* Reset declaration state to declaration specifier. */
>>   static void cp_decl_reset(CPDecl *decl)
>>   {
>> @@ -1071,44 +1087,57 @@ static void cp_decl_gccattribute(CPState *cp, CPDecl *decl)
>>   	attrstr = lj_str_new(cp->L, c+2, attrstr->len-4);
>>   #endif
>>         cp_next(cp);
>> -      switch (attrstr->hash) {
>> -      case H_(64a9208e,8ce14319): case H_(8e6331b2,95a282af):  /* aligned */
>> +      switch (lj_cparse_case(attrstr,
>> +		"\007aligned" "\013__aligned__"
>> +		"\006packed" "\012__packed__"
>> +		"\004mode" "\010__mode__"
>> +		"\013vector_size" "\017__vector_size__"
>> +#if LJ_TARGET_X86
>> +		"\007regparm" "\013__regparm__"
>> +		"\005cdecl"  "\011__cdecl__"
>> +		"\010thiscall" "\014__thiscall__"
>> +		"\010fastcall" "\014__fastcall__"
>> +		"\007stdcall" "\013__stdcall__"
>> +		"\012sseregparm" "\016__sseregparm__"
>> +#endif
>> +	      )) {
>> +      case 0: case 1: /* aligned */
>>   	cp_decl_align(cp, decl);
>>   	break;
>> -      case H_(42eb47de,f0ede26c): case H_(29f48a09,cf383e0c):  /* packed */
>> +      case 2: case 3: /* packed */
>>   	decl->attr |= CTFP_PACKED;
>>   	break;
>> -      case H_(0a84eef6,8dfab04c): case H_(995cf92c,d5696591):  /* mode */
>> +      case 4: case 5: /* mode */
>>   	cp_decl_mode(cp, decl);
>>   	break;
>> -      case H_(0ab31997,2d5213fa): case H_(bf875611,200e9990):  /* vector_size */
>> +      case 6: case 7: /* vector_size */
>>   	{
>>   	  CTSize vsize = cp_decl_sizeattr(cp);
>>   	  if (vsize) CTF_INSERT(decl->attr, VSIZEP, lj_fls(vsize));
>>   	}
>>   	break;
>>   #if LJ_TARGET_X86
>> -      case H_(5ad22db8,c689b848): case H_(439150fa,65ea78cb):  /* regparm */
>> +      case 8: case 9: /* regparm */
>>   	CTF_INSERT(decl->fattr, REGPARM, cp_decl_sizeattr(cp));
>>   	decl->fattr |= CTFP_CCONV;
>>   	break;
>> -      case H_(18fc0b98,7ff4c074): case H_(4e62abed,0a747424):  /* cdecl */
>> +      case 10: case 11: /* cdecl */
>>   	CTF_INSERT(decl->fattr, CCONV, CTCC_CDECL);
>>   	decl->fattr |= CTFP_CCONV;
>>   	break;
>> -      case H_(72b2e41b,494c5a44): case H_(f2356d59,f25fc9bd):  /* thiscall */
>> +      case 12: case 13: /* thiscall */
>>   	CTF_INSERT(decl->fattr, CCONV, CTCC_THISCALL);
>>   	decl->fattr |= CTFP_CCONV;
>>   	break;
>> -      case H_(0d0ffc42,ab746f88): case H_(21c54ba1,7f0ca7e3):  /* fastcall */
>> +      case 14: case 15: /* fastcall */
>>   	CTF_INSERT(decl->fattr, CCONV, CTCC_FASTCALL);
>>   	decl->fattr |= CTFP_CCONV;
>>   	break;
>> -      case H_(ef76b040,9412e06a): case H_(de56697b,c750e6e1):  /* stdcall */
>> +      case 16: case 17: /* stdcall */
>>   	CTF_INSERT(decl->fattr, CCONV, CTCC_STDCALL);
>>   	decl->fattr |= CTFP_CCONV;
>>   	break;
>> -      case H_(ea78b622,f234bd8e): case H_(252ffb06,8d50f34b):  /* sseregparm */
>> +      case 18: case 19: /* sseregparm */
>>   	decl->fattr |= CTF_SSEREGPARM;
>>   	decl->fattr |= CTFP_CCONV;
>>   	break;
>> @@ -1140,16 +1169,13 @@ static void cp_decl_msvcattribute(CPState *cp, CPDecl *decl)
>>     while (cp->tok == CTOK_IDENT) {
>>       GCstr *attrstr = cp->str;
>>       cp_next(cp);
>> -    switch (attrstr->hash) {
>> -    case H_(bc2395fa,98f267f8):  /* align */
>> +    if (cp_str_is(attrstr, "align")) {
>>         cp_decl_align(cp, decl);
>> -      break;
>> -    default:  /* Ignore all other attributes. */
>> +    } else {  /* Ignore all other attributes. */
>>         if (cp_opt(cp, '(')) {
>>   	while (cp->tok != ')' && cp->tok != CTOK_EOF) cp_next(cp);
>>   	cp_check(cp, ')');
>>         }
>> -      break;
>>       }
>>     }
>>     cp_check(cp, ')');
>> @@ -1729,17 +1755,16 @@ static CTypeID cp_decl_abstract(CPState *cp)
>>   static void cp_pragma(CPState *cp, BCLine pragmaline)
>>   {
>>     cp_next(cp);
>> -  if (cp->tok == CTOK_IDENT &&
>> -      cp->str->hash == H_(e79b999f,42ca3e85))  {  /* pack */
>> +  if (cp->tok == CTOK_IDENT && cp_str_is(cp->str, "pack"))  {
>>       cp_next(cp);
>>       cp_check(cp, '(');
>>       if (cp->tok == CTOK_IDENT) {
>> -      if (cp->str->hash == H_(738e923c,a1b65954)) {  /* push */
>> +      if (cp_str_is(cp->str, "push")) {
>>   	if (cp->curpack < CPARSE_MAX_PACKSTACK) {
>>   	  cp->packstack[cp->curpack+1] = cp->packstack[cp->curpack];
>>   	  cp->curpack++;
>>   	}
>> -      } else if (cp->str->hash == H_(6c71cf27,6c71cf27)) {  /* pop */
>> +      } else if (cp_str_is(cp->str, "pop")) {
>>   	if (cp->curpack > 0) cp->curpack--;
>>         } else {
>>   	cp_errmsg(cp, cp->tok, LJ_ERR_XSYMBOL);
>> @@ -1788,13 +1813,11 @@ static void cp_decl_multi(CPState *cp)
>>         if (tok == CTOK_INTEGER) {
>>   	cp_line(cp, hashline);
>>   	continue;
>> -      } else if (tok == CTOK_IDENT &&
>> -		 cp->str->hash == H_(187aab88,fcb60b42)) { /* line */
>> +      } else if (tok == CTOK_IDENT && cp_str_is(cp->str, "line")) {
>>   	if (cp_next(cp) != CTOK_INTEGER) cp_err_token(cp, tok);
>>   	cp_line(cp, hashline);
>>   	continue;
>> -      } else if (tok == CTOK_IDENT &&
>> -	  cp->str->hash == H_(f5e6b4f8,1d509107)) { /* pragma */
>> +      } else if (tok == CTOK_IDENT && cp_str_is(cp->str, "pragma")) {
>>   	cp_pragma(cp, hashline);
>>   	continue;
>>         } else {
>> @@ -1865,8 +1888,6 @@ static void cp_decl_single(CPState *cp)
>>     if (cp->tok != CTOK_EOF) cp_err_token(cp, CTOK_EOF);
>>   }
>>   
>> -#undef H_
>> -
>>   /* ------------------------------------------------------------------------ */
>>   
>>   /* Protected callback for C parser. */
>> diff --git a/src/lj_cparse.h b/src/lj_cparse.h
>> index bad1060b..e40b4047 100644
>> --- a/src/lj_cparse.h
>> +++ b/src/lj_cparse.h
>> @@ -60,6 +60,8 @@ typedef struct CPState {
>>   
>>   LJ_FUNC int lj_cparse(CPState *cp);
>>   
>> +LJ_FUNC int lj_cparse_case(GCstr *str, const char *match);
>> +
>>   #endif
>>   
>>   #endif
>> -- 
>> 2.41.0
>>