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Re: C++ and gather-detailed-mem-stats


On Wed, 15 Aug 2012, Gabriel Dos Reis wrote:

> On Wed, Aug 15, 2012 at 6:01 AM, Richard Guenther <rguenther@suse.de> wrote:
> > On Wed, 15 Aug 2012, Gabriel Dos Reis wrote:
> >
> >> On Wed, Aug 15, 2012 at 5:11 AM, Florian Weimer <fweimer@redhat.com> wrote:
> >> > On 08/15/2012 12:07 PM, Gabriel Dos Reis wrote:
> >> >
> >> >> You might try to encode/package information with the
> >> >> parameters T and A, but essentially you will hit the wall
> >> >> that __FILE__, __LINE__, and __FUNCTION__ are CPP artifacts.
> >> >
> >> >
> >> > GNAT has built-in functions which return this information.
> >>
> >> This is a very sensible thing to do.
> >>
> >> > When they are
> >> > used in default argument expressions and these arguments are omitted, the
> >> > functions are evaluated in the context of the caller and return the file
> >> > position at that point.  Perhaps that would be an approach for C++ as well?
> >>
> >> C++ already has the rule that default arguments are evaluated at the call
> >> site, so this is definitely something to consider for stage 2 and higher builds.
> >> For stage 1 builds, I suppose one would have to fake it and leave
> >> with the imprecision that is bothering Richard?
> >>
> >> > (This assumes that gather-detailed-mem-stats is not needed in the first
> >> > stage compiler.)
> >>
> >> it is built into stage 1 compiler, but I doubt that stage 1 compiler is
> >> really useful to the kind of detailed statistics that would require this.
> >
> > The configury for --enable-gather-detailed-mem-stats is re-done for
> > each stage, so if we add a proper feature check we can simply disable
> > it in stage1 when the host compiler does not support this feature.
> 
> Yes, agreed.
> 
> >
> > We can add __builtin__FILE__ and friends in generic code, for example
> > "folding" them during gimplification using location information on
> > the CALL_EXPR and the current function context.  I think at least
> > __FUNCTION__ is already sort-of a "builtin" as the preprocessor
> > has no way of expanding it.
> 
> Yes, you are right.
> (We already have to treat __PRETTY_FUNCTION__ as a special case
> so that it works reliably for template instances and reports template
> arguments properly.)

Prototype below - fire away on bikeshedding names.

#include <stdio.h>
int main()
{
  printf ("%s (%s): %d\n",
          __builtin_loc_file (),
          __builtin_loc_function (),
          __builtin_loc_line ());
  return 0;
}

prints

> ./t
t.c (main): 4

No fancy trying to share constants for FILE / FUNCTION yet.

Richard.


Index: gcc/builtin-types.def
===================================================================
--- gcc/builtin-types.def	(revision 190407)
+++ gcc/builtin-types.def	(working copy)
@@ -140,6 +140,7 @@ DEF_POINTER_TYPE (BT_PTR_PTR, BT_PTR)
 DEF_FUNCTION_TYPE_0 (BT_FN_VOID, BT_VOID)
 DEF_FUNCTION_TYPE_0 (BT_FN_BOOL, BT_BOOL)
 DEF_FUNCTION_TYPE_0 (BT_FN_PTR, BT_PTR)
+DEF_FUNCTION_TYPE_0 (BT_FN_CONST_STRING, BT_CONST_STRING)
 DEF_FUNCTION_TYPE_0 (BT_FN_PID, BT_PID)
 DEF_FUNCTION_TYPE_0 (BT_FN_INT, BT_INT)
 DEF_FUNCTION_TYPE_0 (BT_FN_UINT, BT_UINT)
Index: gcc/builtins.def
===================================================================
--- gcc/builtins.def	(revision 190407)
+++ gcc/builtins.def	(working copy)
@@ -801,6 +801,11 @@ DEF_BUILTIN_STUB (BUILT_IN_EH_POINTER, "
 DEF_BUILTIN_STUB (BUILT_IN_EH_FILTER, "__builtin_eh_filter")
 DEF_BUILTIN_STUB (BUILT_IN_EH_COPY_VALUES, "__builtin_eh_copy_values")
 
+/* __FILE__, __LINE__, __FUNCTION__ as builtins.  */
+DEF_GCC_BUILTIN (BUILT_IN_LOC_FILE, "loc_file", BT_FN_CONST_STRING, ATTR_CONST_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN (BUILT_IN_LOC_FUNCTION, "loc_function", BT_FN_CONST_STRING, ATTR_CONST_NOTHROW_LEAF_LIST)
+DEF_GCC_BUILTIN (BUILT_IN_LOC_LINE, "loc_line", BT_FN_INT, ATTR_CONST_NOTHROW_LEAF_LIST)
+
 /* Synchronization Primitives.  */
 #include "sync-builtins.def"
 
Index: gcc/gimplify.c
===================================================================
--- gcc/gimplify.c	(revision 190407)
+++ gcc/gimplify.c	(working copy)
@@ -2528,6 +2528,28 @@ gimplify_call_expr (tree *expr_p, gimple
 	      return GS_OK;
 	    }
 	}
+      else if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
+	       && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_LOC_LINE)
+	{
+	  expanded_location loc = expand_location (EXPR_LOCATION (*expr_p));
+	  *expr_p = build_int_cst (TREE_TYPE (*expr_p), loc.line);
+	  return GS_OK;
+	}
+      else if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
+	       && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_LOC_FILE)
+	{
+	  expanded_location loc = expand_location (EXPR_LOCATION (*expr_p));
+	  *expr_p = build_string_literal (strlen (loc.file) + 1, loc.file);
+	  return GS_OK;
+	}
+      else if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_NORMAL
+	       && DECL_FUNCTION_CODE (fndecl) == BUILT_IN_LOC_FUNCTION)
+	{
+	  const char *function;
+	  function = IDENTIFIER_POINTER (DECL_NAME (current_function_decl));
+	  *expr_p = build_string_literal (strlen (function) + 1, function);
+	  return GS_OK;
+	}
     }
 
   /* Remember the original function pointer type.  */


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