Re: [tuples] walk_tree for tuples

[Aldy Hernandez <aldyh at redhat dot com>]

My apologies Chris.  You're right.  There is no 1 off error.

The problem was that I was assuming gs_switch_*label would return the
default label with an index of 0.  Diego also agrees this should be the
case, so I'm reverting my one off changes, but removing the "+ 1" in
gs_switch_label and gs_switch_set_label.

Can you double check the logic to make sure I didn't botch something up?

> This has been a source of confusion for me, but I *think* there is an
> extra 1 tree's worth added in because of the wacky memory allocation
> in the back of:
> 
> > tree index;
> > tree GTY ((length ("%h.nlabels + 1"))) labels[1];

Correct.

> so, should it be nlabels + default - the one extra?

Yes.  Fixed.

Sorry about the confusion.

Committing to branch.
 
	* gimple-ir.c (gs_build_switch_1): Allocate one less tree.
	(gs_build_switch_1): Offset labels by one.
	(gs_switch_label): Same.
	(gs_switch_set_label): Same.

Index: gimple-ir.c
===================================================================
--- gimple-ir.c	(revision 126596)
+++ gimple-ir.c	(working copy)
@@ -437,9 +437,9 @@ gs_build_switch_1 (unsigned int nlabels,
 {
   gimple p;
   
-  /* nlabels + default label.  */
-  p = ggc_alloc_cleared ( sizeof (struct gimple_statement_switch)
-                          + (sizeof (tree) * (nlabels + 1)));
+  /* nlabels + 1 default label - 1 extra from struct.  */
+  p = ggc_alloc_cleared (sizeof (struct gimple_statement_switch)
+                         + sizeof (tree) * nlabels);
   GS_CODE (p) = GS_SWITCH;
 
   gs_switch_set_nlabels (p, nlabels);
@@ -475,7 +475,7 @@ gs_build_switch (unsigned int nlabels, t
 /* Construct a GS_SWITCH statement.
 
    INDEX is the switch's index.
-   NLABLES is the number of labels in the switch excluding the default. 
+   NLABELS is the number of labels in the switch excluding the default. 
    ARGS is a vector of labels excluding the default.  */
 
 gimple
@@ -486,7 +486,7 @@ gs_build_switch_vec (tree index, tree de
   gimple p = gs_build_switch_1 (nlabels, index, default_label);
 
   for (i = 0; i < nlabels; i++)
-    gs_switch_set_label (p, i, VEC_index (tree, args, i));
+    gs_switch_set_label (p, i + 1, VEC_index (tree, args, i));
 
   return p;
 }
Index: gimple-ir.h
===================================================================
--- gimple-ir.h	(revision 126596)
+++ gimple-ir.h	(working copy)
@@ -1067,20 +1067,25 @@ gs_switch_set_default_label (gimple gs, 
   gs->gs_switch.labels[0] = label;
 }
 
+/* Return the label numbered INDEX.  The default label is 0, followed by any
+   labels in a switch statement.  */
+
 static inline tree
 gs_switch_label (gimple gs, int index)
 {
   GS_CHECK (gs, GS_SWITCH);
   gcc_assert ((unsigned)index <= gs->gs_switch.nlabels);
-  return gs->gs_switch.labels[index + 1];
+  return gs->gs_switch.labels[index];
 }
 
+/* Set the label number INDEX to LABEL.  0 is always the default label.  */
+
 static inline void
 gs_switch_set_label (gimple gs, int index, tree label)
 {
   GS_CHECK (gs, GS_SWITCH);
   gcc_assert ((unsigned)index <= gs->gs_switch.nlabels);
-  gs->gs_switch.labels[index + 1] = label;
+  gs->gs_switch.labels[index] = label;
 }
 
 /* GS_OMP_* accessors. */