Re: M4 1.4.10b [beta] released

Hi Eric,

> > | Effects on "autoconf" in gettext/gettext-tools:
> > |
> > | m4-1.4.10      50.6 s real + 1.0 sec system
> > | m4-1.4.10b     42.1 s real + 0.9 sec system
> 
> And with --disable-assert, I get:
> 
>                    41.2 s real + 0.9 sec system

With the patch below, I get:

                     36.9 s real + 0.9 sec system

i.e. an additional 10% speedup.

The speed-relevant code is only the case for INPUT_CHAIN. I added the one
for INPUT_STRING because it may be useful it situations I don't know of.


2008-02-28  Bruno Haible  <[email protected]>

	Optimize a code path frequently exercised by autoconf.
	Memory impact: none.
	Speed impact: 10% speedup.
	* src/input.c (next_token): Add an optimized code path for the
	frequent case of rescanning chains or strings.

*** src/input.c.bak	2008-02-23 18:13:02.000000000 +0100
--- src/input.c	2008-02-28 14:52:02.000000000 +0100
***************
*** 1632,1637 ****
--- 1632,1741 ----
        quote_level = 1;
        while (1)
  	{
+ 	  if (curr_quote.len1 == 1 && curr_quote.len2 == 1 && !input_change
+ 	      && isp)
+ 	    {
+ 	      /* The optimized case.  It heavily inlines the MATCH macro and
+ 		 the next_char and next_char_1 functions, to the point that
+ 		 the scan is a loop over a region of memory followed by a
+ 		 simple memory copy operation.
+ 		 The case with INPUT_CHAIN alone can speed up GNU autoconf
+ 		 runs by 10%.  */
+ 	      if (isp->type == INPUT_CHAIN)
+ 		{
+ 		  token_chain *chain = isp->u.u_c.chain;
+ 
+ 		  if (chain)
+ 		    {
+ 		      if (obs != NULL && current_quote_age
+ 			  && chain->quote_age == current_quote_age)
+ 			{
+ 			  /* next_char () would return CHAR_QUOTE here.  */
+ 			  append_quote_token (obs, td);
+ 			}
+ 		      else if (chain->type == CHAIN_STR && chain->u.u_s.len > 0)
+ 			{
+ 			  unsigned char curr_quote_1 =
+ 			    to_uchar (curr_quote.str1[0]);
+ 			  unsigned char curr_quote_2 =
+ 			    to_uchar (curr_quote.str2[0]);
+ 			  const char *p;
+ 			  size_t n;
+ 			  size_t count;
+ 
+ 			  /* Partial consumption invalidates quote age.  */
+ 			  chain->quote_age = 0;
+ 
+ 			  p = chain->u.u_s.str;
+ 			  n = chain->u.u_s.len;
+ 			  do
+ 			    {
+ 			      unsigned char ch = to_uchar (*p);
+ 			      if (ch == curr_quote_2)
+ 				{
+ 				  if (--quote_level == 0)
+ 				    break;
+ 				}
+ 			      else
+ 				quote_level += (ch == curr_quote_1);
+ 			      p++;
+ 			      n--;
+ 			    }
+ 			  while (n > 0);
+ 
+ 			  count = p - chain->u.u_s.str;
+ 			  if (count > 0)
+ 			    obstack_grow (obs_td, chain->u.u_s.str, count);
+ 			  count += (quote_level == 0);
+ 			  chain->u.u_s.str += count;
+ 			  chain->u.u_s.len -= count;
+ 			  if (quote_level == 0)
+ 			    break;
+ 			  continue;
+ 			}
+ 		    }
+ 		}
+ 	      else if (isp->type == INPUT_STRING)
+ 		{
+ 		  if (isp->u.u_s.len > 0)
+ 		    {
+ 		      unsigned char curr_quote_1 =
+ 			to_uchar (curr_quote.str1[0]);
+ 		      unsigned char curr_quote_2 =
+ 			to_uchar (curr_quote.str2[0]);
+ 		      const char *p = isp->u.u_s.str;
+ 		      size_t n = isp->u.u_s.len;
+ 		      size_t count;
+ 
+ 		      do
+ 			{
+ 			  unsigned char ch = to_uchar (*p);
+ 			  if (ch == curr_quote_2)
+ 			    {
+ 			      if (--quote_level == 0)
+ 				break;
+ 			    }
+ 			  else
+ 			    quote_level += (ch == curr_quote_1);
+ 			  p++;
+ 			  n--;
+ 			}
+ 		      while (n > 0);
+ 
+ 		      count = p - isp->u.u_s.str;
+ 		      if (count > 0)
+ 			obstack_grow (obs_td, isp->u.u_s.str, count);
+ 		      count += (quote_level == 0);
+ 		      isp->u.u_s.str += count;
+ 		      isp->u.u_s.len -= count;
+ 		      if (quote_level == 0)
+ 			break;
+ 		      continue;
+ 		    }
+ 		}
+ 	    }
+ 
+ 	  /* The general case.  Proceed character by character.  */
  	  ch = next_char (obs != NULL && current_quote_age);
  	  if (ch == CHAR_EOF)
  	    /* Current_file changed to "" if we see CHAR_EOF, use