Re: [FORTRAN PATCH] Reduce gfc_match_strings usage (part 2)

[Tobias Schlüter <tobias dot schlueter at physik dot uni-muenchen dot de>]

Tobias Schlüter wrote:
> Presumably the biggest speedup can be obtained by eating ',' followed by 
> whitespace before the call to gfc_match_strings in decl.c:2161, and 
> matching double colons separately, as this is a case where valid code 
> will have to backup insanely often.

I was overestimating gfc_match-strings' badness when I wrote this: as 
gfc_match_strings will only read each source character once, there's no 
backing up between matching individual strings, and the performance gain 
of my suggested approach would be much smaller than I had thought: the 
only differences would be that one comparison against a NULL pointer 
(for DECL_COLON) would be omitted per loop iteration, and the comparison 
of the first few characters against ", " would only be done once.

Nevertheless, I implemented my suggestion in the attached patch, and I 
would be grateful if you could check its effect on the profile, FX. 
Patch built on i386-darwin, so far it holds up against the testsuite.

Thanks,
- Tobi

2007-03-11  Tobias Schlüter  <tobi@gcc.gnu.org>

	* decl.c (decls): Only keep attributes in array, remove
	leading ", ".
	(match_attr_spec): Match double colon and attribute separators
	separately from attributes.	

Index: gcc/fortran/decl.c
===================================================================
--- gcc/fortran/decl.c	(revision 122819)
+++ gcc/fortran/decl.c	(working copy)
@@ -2118,24 +2118,23 @@ match_attr_spec (void)
 #define NUM_DECL GFC_DECL_END
 
   static mstring decls[] = {
-    minit (", allocatable", DECL_ALLOCATABLE),
-    minit (", dimension", DECL_DIMENSION),
-    minit (", external", DECL_EXTERNAL),
-    minit (", intent ( in )", DECL_IN),
-    minit (", intent ( out )", DECL_OUT),
-    minit (", intent ( in out )", DECL_INOUT),
-    minit (", intrinsic", DECL_INTRINSIC),
-    minit (", optional", DECL_OPTIONAL),
-    minit (", parameter", DECL_PARAMETER),
-    minit (", pointer", DECL_POINTER),
-    minit (", protected", DECL_PROTECTED),
-    minit (", private", DECL_PRIVATE),
-    minit (", public", DECL_PUBLIC),
-    minit (", save", DECL_SAVE),
-    minit (", target", DECL_TARGET),
-    minit (", value", DECL_VALUE),
-    minit (", volatile", DECL_VOLATILE),
-    minit ("::", DECL_COLON),
+    minit ("allocatable", DECL_ALLOCATABLE),
+    minit ("dimension", DECL_DIMENSION),
+    minit ("external", DECL_EXTERNAL),
+    minit ("intent ( in )", DECL_IN),
+    minit ("intent ( out )", DECL_OUT),
+    minit ("intent ( in out )", DECL_INOUT),
+    minit ("intrinsic", DECL_INTRINSIC),
+    minit ("optional", DECL_OPTIONAL),
+    minit ("parameter", DECL_PARAMETER),
+    minit ("pointer", DECL_POINTER),
+    minit ("protected", DECL_PROTECTED),
+    minit ("private", DECL_PRIVATE),
+    minit ("public", DECL_PUBLIC),
+    minit ("save", DECL_SAVE),
+    minit ("target", DECL_TARGET),
+    minit ("value", DECL_VALUE),
+    minit ("volatile", DECL_VOLATILE),
     minit (NULL, DECL_NONE)
   };
 
@@ -2158,8 +2157,21 @@ match_attr_spec (void)
 
   for (;;)
     {
+      gfc_gobble_whitespace ();
+      if (gfc_match ("::") == MATCH_YES)
+	{
+	  d = DECL_COLON;
+	  break;
+	}
+
+      if (gfc_match (", ") != MATCH_YES)
+	{
+	  d = DECL_NONE;
+	  break;
+	}
+
       d = (decl_types) gfc_match_strings (decls);
-      if (d == DECL_NONE || d == DECL_COLON)
+      if (d == DECL_NONE)
 	break;
        
       seen[d]++;