[PCH] cache memory for cselib_init

[Geoffrey Keating <geoffk at romulus dot sfbay dot redhat dot com>]

I didn't think cselib_init would get called hundreds of times
to allocate space for thousands of registers, but this happens
while building expr.o on the sparc bootstrap.

Bootstrapped & tested on i686-pc-linux.

-- 
Geoff Keating <geoffk@redhat.com>

===File ~/patches/pchbranch-csemingc.patch==================
2002-05-30  Geoffrey Keating  <geoffk@redhat.com>

	* varray.h (VARRAY_CLEAR): New.
	(varray_clear): Prototype.
	* varray.c (varray_clear): New.
	* cselib.c (reg_values_old): New.
	(used_regs_old): New.
	(cselib_init): Use cached varrays if available to avoid
	generating large amounts of garbage.
	(cselib_finish): Don't throw away old varrays.

Index: varray.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/varray.c,v
retrieving revision 1.14.2.2
diff -p -u -p -r1.14.2.2 varray.c
--- varray.c	23 May 2002 19:28:48 -0000	1.14.2.2
+++ varray.c	31 May 2002 08:10:36 -0000
@@ -106,6 +106,17 @@ varray_grow (va, n)
   return va;
 }
 
+/* Reset a varray to its original state.  */
+void
+varray_clear (va)
+     varray_type va;
+{
+  size_t data_size = element_size[va->type] * va->num_elements;
+
+  memset (va->data.c, 0, data_size);
+  va->elements_used = 0;
+}
+
 /* Check the bounds of a varray access.  */
 
 #if defined ENABLE_CHECKING && (GCC_VERSION >= 2007)
Index: varray.h
===================================================================
RCS file: /cvs/gcc/gcc/gcc/varray.h,v
retrieving revision 1.24.12.5
diff -p -u -p -r1.24.12.5 varray.h
--- varray.h	23 May 2002 19:28:48 -0000	1.24.12.5
+++ varray.h	31 May 2002 08:10:36 -0000
@@ -217,6 +217,10 @@ extern varray_type varray_grow	PARAMS ((
 #define VARRAY_ACTIVE_SIZE(VA)	((VA)->elements_used)
 #define VARRAY_POP_ALL(VA)	((VA)->elements_used = 0)
 
+#define VARRAY_CLEAR(VA) varray_clear(VA)
+
+extern void varray_clear	PARAMS ((varray_type));
+
 /* Check for VARRAY_xxx macros being in bound.  */
 #if defined ENABLE_CHECKING && (GCC_VERSION >= 2007)
 extern void varray_check_failed PARAMS ((varray_type, size_t,
Index: cselib.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/cselib.c,v
retrieving revision 1.15.6.4
diff -p -u -p -r1.15.6.4 cselib.c
--- cselib.c	23 May 2002 19:28:42 -0000	1.15.6.4
+++ cselib.c	31 May 2002 08:10:36 -0000
@@ -101,11 +101,13 @@ static int n_useless_values;
    pointers to cselib_val structures, but rather elt_lists.  The purpose is
    to be able to refer to the same register in different modes.  */
 static GTY(()) varray_type reg_values;
+static GTY((deletable (""))) varray_type reg_values_old;
 #define REG_VALUES(I) VARRAY_ELT_LIST (reg_values, (I))
 
 /* Here the set of indices I with REG_VALUES(I) != 0 is saved.  This is used
    in clear_table() for fast emptying.  */
 static GTY(()) varray_type used_regs;
+static GTY((deletable (""))) varray_type used_regs_old;
 
 /* We pass this to cselib_invalidate_mem to invalidate all of
    memory for a non-const call instruction.  */
@@ -1358,8 +1360,18 @@ cselib_init ()
     callmem = gen_rtx_MEM (BLKmode, const0_rtx);
 
   cselib_nregs = max_reg_num ();
-  VARRAY_ELT_LIST_INIT (reg_values, cselib_nregs, "reg_values");
-  VARRAY_UINT_INIT (used_regs, cselib_nregs, "used_regs");
+  if (reg_values_old != NULL && VARRAY_SIZE (reg_values_old) >= cselib_nregs)
+    {
+      reg_values = reg_values_old;
+      used_regs = used_regs_old;
+      VARRAY_CLEAR (reg_values);
+      VARRAY_CLEAR (used_regs);
+    }
+  else
+    {
+      VARRAY_ELT_LIST_INIT (reg_values, cselib_nregs, "reg_values");
+      VARRAY_UINT_INIT (used_regs, cselib_nregs, "used_regs");
+    }
   hash_table = htab_create_ggc (31, get_value_hash, entry_and_rtx_equal_p, 
 				NULL);
   clear_table (1);
@@ -1370,7 +1382,9 @@ cselib_init ()
 void
 cselib_finish ()
 {
+  reg_values_old = reg_values;
   reg_values = 0;
+  used_regs_old = used_regs;
   used_regs = 0;
   hash_table = 0;
   n_useless_values = 0;
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