Re: [PATCH] Fix PR52977

[Michael Matz <matz at suse dot de>]

Hi,

On Mon, 16 Apr 2012, Richard Guenther wrote:

> This fixes PR52977 - for PCH to work with its pointer relocation code we 
> have to avoid dereferencing pointers to compute array lengths in 
> structures.  So we have to unfortunately keep duplicated info about 
> VECTOR_CST vector lengths.

That's a pity and caused me to look a bit at gengtype.  We can do better, 
and compute the lengths before all fields are accessed (and mangled in the 
PCH case).  With the patch below we emit such code:

        case TS_VECTOR:
          {
            size_t l0 = (size_t)(TYPE_VECTOR_SUBPARTS (TREE_TYPE ((tree)&((*x).generic.vector))));
            if ((void *)(x) == this_obj)
              op (&((*x).generic.vector.typed.type), cookie);
            {
              size_t i0;
              for (i0 = 0; i0 != l0; i0++) {
                if ((void *)(x) == this_obj)
                  op (&((*x).generic.vector.elts[i0]), cookie);
              }
            }
          }

Note how .generic.vector.typed.type is only mangled after TREE_TYPE is 
used to calculate the length.

I regstrapped this on x86_64-linux, all languages, no regression.  Okay 
for trunk (saving the all-important memory for vector constants again :) 
)?


Ciao,
Michael.
------------------
	PR middle-end/52977
	* tree.h (VECTOR_CST_NELTS): Use part number of types again.
	(struct tree_vector): Adjust GTY length.
	* tree.c (make_vector_stat): Don't set VECTOR_CST_NELTS.

	* gengtype.c (struct walk_type_data): Add in_record_p and loopcounter
	members.
	(walk_type, <TYPE_POINTER, TYPE_ARRAY>): Handle case where our
	caller emitted the length calulation already.
	(walk_type, <TYPE_UNION, TYPE_STRUCT>): Emit length calculations
	before handling any of the fields for structs.

Index: tree.h
===================================================================
--- tree.h	(revision 186580)
+++ tree.h	(working copy)
@@ -1534,14 +1534,13 @@ struct GTY(()) tree_complex {
 };
 
 /* In a VECTOR_CST node.  */
-#define VECTOR_CST_NELTS(NODE) (VECTOR_CST_CHECK (NODE)->vector.length)
+#define VECTOR_CST_NELTS(NODE) (TYPE_VECTOR_SUBPARTS (TREE_TYPE (NODE)))
 #define VECTOR_CST_ELTS(NODE) (VECTOR_CST_CHECK (NODE)->vector.elts)
 #define VECTOR_CST_ELT(NODE,IDX) (VECTOR_CST_CHECK (NODE)->vector.elts[IDX])
 
 struct GTY(()) tree_vector {
   struct tree_typed typed;
-  unsigned length;
-  tree GTY ((length ("%h.length"))) elts[1];
+  tree GTY ((length ("TYPE_VECTOR_SUBPARTS (TREE_TYPE ((tree)&%h))"))) elts[1];
 };
 
 #include "symtab.h"
Index: tree.c
===================================================================
--- tree.c	(revision 186580)
+++ tree.c	(working copy)
@@ -1329,7 +1329,6 @@ make_vector_stat (unsigned len MEM_STAT_
 
   TREE_SET_CODE (t, VECTOR_CST);
   TREE_CONSTANT (t) = 1;
-  VECTOR_CST_NELTS (t) = len;
 
   return t;
 }
Index: gengtype.c
===================================================================
--- gengtype.c	(revision 186580)
+++ gengtype.c	(working copy)
@@ -2291,6 +2291,8 @@ struct walk_type_data
   const char *reorder_fn;
   bool needs_cast_p;
   bool fn_wants_lvalue;
+  bool in_record_p;
+  int loopcounter;
 };
 
 /* Print a mangled name representing T to OF.  */
@@ -2592,7 +2594,7 @@ walk_type (type_p t, struct walk_type_da
 	  }
 	else
 	  {
-	    int loopcounter = d->counter++;
+	    int loopcounter = d->loopcounter;
 	    const char *oldval = d->val;
 	    const char *oldprevval3 = d->prev_val[3];
 	    char *newval;
@@ -2602,7 +2604,10 @@ walk_type (type_p t, struct walk_type_da
 	    oprintf (d->of, "%*ssize_t i%d;\n", d->indent, "", loopcounter);
 	    oprintf (d->of, "%*sfor (i%d = 0; i%d != (size_t)(", d->indent,
 		     "", loopcounter, loopcounter);
-	    output_escaped_param (d, length, "length");
+	    if (!d->in_record_p)
+	      output_escaped_param (d, length, "length");
+	    else
+	      oprintf (d->of, "l%d", loopcounter);
 	    oprintf (d->of, "); i%d++) {\n", loopcounter);
 	    d->indent += 2;
 	    d->val = newval = xasprintf ("%s[i%d]", oldval, loopcounter);
@@ -2624,7 +2629,7 @@ walk_type (type_p t, struct walk_type_da
 
     case TYPE_ARRAY:
       {
-	int loopcounter = d->counter++;
+	int loopcounter;
 	const char *oldval = d->val;
 	char *newval;
 
@@ -2633,6 +2638,11 @@ walk_type (type_p t, struct walk_type_da
 	if (t->u.a.p->kind == TYPE_SCALAR)
 	  break;
 
+	if (length)
+	  loopcounter = d->loopcounter;
+	else
+	  loopcounter = d->counter++;
+
 	/* When walking an array, compute the length and store it in a
 	   local variable before walking the array elements, instead of
 	   recomputing the length expression each time through the loop.
@@ -2643,13 +2653,16 @@ walk_type (type_p t, struct walk_type_da
 	oprintf (d->of, "%*s{\n", d->indent, "");
 	d->indent += 2;
 	oprintf (d->of, "%*ssize_t i%d;\n", d->indent, "", loopcounter);
-	oprintf (d->of, "%*ssize_t l%d = (size_t)(",
-		 d->indent, "", loopcounter);
-	if (length)
-	  output_escaped_param (d, length, "length");
-	else
-	  oprintf (d->of, "%s", t->u.a.len);
-	oprintf (d->of, ");\n");
+	if (!d->in_record_p || !length)
+	  {
+	    oprintf (d->of, "%*ssize_t l%d = (size_t)(",
+		     d->indent, "", loopcounter);
+	    if (length)
+	      output_escaped_param (d, length, "length");
+	    else
+	      oprintf (d->of, "%s", t->u.a.len);
+	    oprintf (d->of, ");\n");
+	  }
 
 	oprintf (d->of, "%*sfor (i%d = 0; i%d != l%d; i%d++) {\n",
 		 d->indent, "",
@@ -2678,6 +2691,9 @@ walk_type (type_p t, struct walk_type_da
 	const int union_p = t->kind == TYPE_UNION;
 	int seen_default_p = 0;
 	options_p o;
+	int lengths_seen = 0;
+	int endcounter;
+	bool any_length_seen = false;
 
 	if (!t->u.s.line.file)
 	  error_at_line (d->line, "incomplete structure `%s'", t->u.s.tag);
@@ -2713,6 +2729,45 @@ walk_type (type_p t, struct walk_type_da
 	    d->indent += 2;
 	    oprintf (d->of, "%*s{\n", d->indent, "");
 	  }
+
+	for (f = t->u.s.fields; f; f = f->next)
+	  {
+	    options_p oo;
+	    int skip_p = 0;
+	    const char *fieldlength = NULL;
+
+	    d->reorder_fn = NULL;
+	    for (oo = f->opt; oo; oo = oo->next)
+	      if (strcmp (oo->name, "skip") == 0)
+		skip_p = 1;
+	      else if (strcmp (oo->name, "length") == 0
+		       && oo->kind == OPTION_STRING)
+		fieldlength = oo->info.string;
+
+	    if (skip_p)
+	      continue;
+	    if (fieldlength)
+	      {
+	        lengths_seen++;
+		d->counter++;
+		if (!union_p)
+		  {
+		    if (!any_length_seen)
+		      {
+			oprintf (d->of, "%*s{\n", d->indent, "");
+			d->indent += 2;
+		      }
+		    any_length_seen = true;
+
+		    oprintf (d->of, "%*ssize_t l%d = (size_t)(",
+			     d->indent, "", d->counter - 1);
+		    output_escaped_param (d, fieldlength, "length");
+		    oprintf (d->of, ");\n");
+		  }
+	      }
+	  }
+	endcounter = d->counter;
+
 	for (f = t->u.s.fields; f; f = f->next)
 	  {
 	    options_p oo;
@@ -2721,6 +2776,7 @@ walk_type (type_p t, struct walk_type_da
 	    int skip_p = 0;
 	    int default_p = 0;
 	    int use_param_p = 0;
+	    const char *fieldlength = NULL;
 	    char *newval;
 
 	    d->reorder_fn = NULL;
@@ -2741,6 +2797,9 @@ walk_type (type_p t, struct walk_type_da
 	      else if (strncmp (oo->name, "use_param", 9) == 0
 		       && (oo->name[9] == '\0' || ISDIGIT (oo->name[9])))
 		use_param_p = 1;
+	      else if (strcmp (oo->name, "length") == 0
+		       && oo->kind == OPTION_STRING)
+		fieldlength = oo->info.string;
 
 	    if (skip_p)
 	      continue;
@@ -2774,16 +2833,24 @@ walk_type (type_p t, struct walk_type_da
 			     "field `%s' is missing `tag' or `default' option",
 			     f->name);
 
+	    if (fieldlength)
+	      {
+		d->loopcounter = endcounter - lengths_seen--;
+	      }
+
 	    d->line = &f->line;
 	    d->val = newval = xasprintf ("%s%s%s", oldval, dot, f->name);
 	    d->opt = f->opt;
 	    d->used_length = false;
+	    d->in_record_p = !union_p;
 
 	    if (union_p && use_param_p && d->param == NULL)
 	      oprintf (d->of, "%*sgcc_unreachable ();\n", d->indent, "");
 	    else
 	      walk_type (f->type, d);
 
+	    d->in_record_p = false;
+
 	    free (newval);
 
 	    if (union_p)
@@ -2808,6 +2875,11 @@ walk_type (type_p t, struct walk_type_da
 	    oprintf (d->of, "%*s}\n", d->indent, "");
 	    d->indent -= 2;
 	  }
+	if (any_length_seen)
+	  {
+	    d->indent -= 2;
+	    oprintf (d->of, "%*s}\n", d->indent, "");
+	  }
       }
       break;