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

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

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
hardcoded string hashes) with search in the given string with the
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