Re: [PATCH] Extend lazy computation of expensive preprocessor macros to FLOATN*

[Jakub Jelinek <jakub at redhat dot com>]

On Fri, Jan 26, 2018 at 11:22:04PM +0000, Joseph Myers wrote:
> On Sat, 27 Jan 2018, Jakub Jelinek wrote:
> > Honza reported today on IRC that we spent (again) significant time
> > of empty file compilation computing preprocessor *_MAX/*_MIN etc. macros.
> > In 2010 I've added lazy computation for these, only when they are first used
> > except for -dD, but reserved just 12 entries for those, as only
> > FLT/DBL/LDBL prefixed macros (4 times for each kind) were needed at that
> > point.  In 2016 for PR32187 Joseph has added a bunch of other kinds and
> > because there is no space in the array reserved for those, they are
> > evaluated right away, which is quite expensive.
> > 
> > The following patch makes them lazy again.
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
> 
> Rather than hardcoding a number 36 I'd rather it used an explicit 
> computation (with explanatory comment) such as 4 * (3 + 
> NUM_FLOATN_NX_TYPES) (if that is indeed a safe value to use to guarantee 
> covering all these types).

Works for me, this tests fine on a couple of tests, ok for trunk if it
passes bootstrap/regtest?

2018-01-27  Jakub Jelinek  <jakub@redhat.com>

	* c-cppbuiltin.c (c_cpp_builtins): Use ggc_strdup for the fp_suffix
	argument.
	(LAZY_HEX_FP_VALUES_CNT): Define.
	(lazy_hex_fp_values): Allow up to LAZY_HEX_FP_VALUES_CNT lazy hex fp
	values rather than just 12.
	(builtin_define_with_hex_fp_value): Likewise.

	* include/cpplib.h (enum cpp_builtin_type): Change BT_LAST_USER from
	BT_FIRST_USER + 31 to BT_FIRST_USER + 63.

--- gcc/c-family/c-cppbuiltin.c.jj	2018-01-03 10:20:21.369538150 +0100
+++ gcc/c-family/c-cppbuiltin.c	2018-01-26 11:01:15.266648197 +0100
@@ -1124,8 +1124,8 @@ c_cpp_builtins (cpp_reader *pfile)
 	       floatn_nx_types[i].extended ? "X" : "");
       sprintf (csuffix, "F%d%s", floatn_nx_types[i].n,
 	       floatn_nx_types[i].extended ? "x" : "");
-      builtin_define_float_constants (prefix, csuffix, "%s", csuffix,
-				      FLOATN_NX_TYPE_NODE (i));
+      builtin_define_float_constants (prefix, ggc_strdup (csuffix), "%s",
+				      csuffix, FLOATN_NX_TYPE_NODE (i));
     }
 
   /* For decfloat.h.  */
@@ -1571,7 +1571,14 @@ struct GTY(()) lazy_hex_fp_value_struct
   int digits;
   const char *fp_suffix;
 };
-static GTY(()) struct lazy_hex_fp_value_struct lazy_hex_fp_values[12];
+/* Number of the expensive to compute macros we should evaluate lazily.
+   Each builtin_define_float_constants invocation calls
+   builtin_define_with_hex_fp_value 4 times and builtin_define_float_constants
+   is called for FLT, DBL, LDBL and up to NUM_FLOATN_NX_TYPES times for
+   FLTNN*.  */ 
+#define LAZY_HEX_FP_VALUES_CNT (4 * (3 + NUM_FLOATN_NX_TYPES))
+static GTY(()) struct lazy_hex_fp_value_struct
+  lazy_hex_fp_values[LAZY_HEX_FP_VALUES_CNT];
 static GTY(()) int lazy_hex_fp_value_count;
 
 static bool
@@ -1616,7 +1623,7 @@ builtin_define_with_hex_fp_value (const
   char dec_str[64], buf[256], buf1[128], buf2[64];
 
   /* This is very expensive, so if possible expand them lazily.  */
-  if (lazy_hex_fp_value_count < 12
+  if (lazy_hex_fp_value_count < LAZY_HEX_FP_VALUES_CNT
       && flag_dump_macros == 0
       && !cpp_get_options (parse_in)->traditional)
     {
--- libcpp/include/cpplib.h.jj	2018-01-18 21:11:59.890207215 +0100
+++ libcpp/include/cpplib.h	2018-01-26 10:58:10.249699482 +0100
@@ -719,7 +719,7 @@ enum cpp_builtin_type
   BT_COUNTER,			/* `__COUNTER__' */
   BT_HAS_ATTRIBUTE,		/* `__has_attribute__(x)' */
   BT_FIRST_USER,		/* User defined builtin macros.  */
-  BT_LAST_USER = BT_FIRST_USER + 31
+  BT_LAST_USER = BT_FIRST_USER + 63
 };
 
 #define CPP_HASHNODE(HNODE)	((cpp_hashnode *) (HNODE))


	Jakub