[PATCH] Introduce emit_status::ensure_regno_capacity (v5)

[David Malcolm <dmalcolm@redhat.com>]

On Wed, 2016-10-05 at 17:55 +0200, Bernd Schmidt wrote:
> On 10/05/2016 06:15 PM, David Malcolm wrote:
> > -  /* Make sure regno_pointer_align, and regno_reg_rtx are large
> > -     enough to have an element for this pseudo reg number.  */
> > +  int cur_size = crtl->emit.regno_pointer_align_length;
> > +  if (reg_rtx_no == cur_size)
> > +    crtl->emit.ensure_regno_capacity (cur_size * 2);
> 
> Patch looks ok in principle, but maybe this manipulation of the size
> should be part of the new function as well - i.e. don't pass a
> new_size
> to it, make it check reg_rtx_no itself.

Changed in this version
- dropped "new_size" argument
- added a while loop to cover the case where reg_rtx_no
  needs to grow by more the double (potentially needed
  when loading RTL dumps)
- added a gcc_assert to ensure that the buffer is large enough

Successfully bootstrapped&regrtested on x86_64-pc-linux-gnu as
part of the patch kit.

OK for trunk? (assuming it tests OK individually)

gcc/ChangeLog:
	* emit-rtl.c (gen_reg_rtx): Move regno_pointer_align and
	regno_reg_rtx resizing logic to...
	(emit_status::ensure_regno_capacity): ...this new method,
	and ensure that the buffers are large enough.
	(init_emit): Allocate regno_reg_rtx using ggc_cleared_vec_alloc
	rather than ggc_vec_alloc.
	* function.h (emit_status::ensure_regno_capacity): New method.
---
 gcc/emit-rtl.c | 48 +++++++++++++++++++++++++++++-------------------
 gcc/function.h |  2 ++
 2 files changed, 31 insertions(+), 19 deletions(-)

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index e995899..b2b5fde 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -1057,29 +1057,38 @@ gen_reg_rtx (machine_mode mode)
   /* Do not call gen_reg_rtx with uninitialized crtl.  */
   gcc_assert (crtl->emit.regno_pointer_align_length);
 
-  /* Make sure regno_pointer_align, and regno_reg_rtx are large
-     enough to have an element for this pseudo reg number.  */
+  crtl->emit.ensure_regno_capacity ();
+  gcc_assert (reg_rtx_no < crtl->emit.regno_pointer_align_length);
 
-  if (reg_rtx_no == crtl->emit.regno_pointer_align_length)
-    {
-      int old_size = crtl->emit.regno_pointer_align_length;
-      char *tmp;
-      rtx *new1;
+  val = gen_raw_REG (mode, reg_rtx_no);
+  regno_reg_rtx[reg_rtx_no++] = val;
+  return val;
+}
 
-      tmp = XRESIZEVEC (char, crtl->emit.regno_pointer_align, old_size * 2);
-      memset (tmp + old_size, 0, old_size);
-      crtl->emit.regno_pointer_align = (unsigned char *) tmp;
+/* Make sure m_regno_pointer_align, and regno_reg_rtx are large
+   enough to have elements in the range 0 <= idx <= reg_rtx_no.  */
 
-      new1 = GGC_RESIZEVEC (rtx, regno_reg_rtx, old_size * 2);
-      memset (new1 + old_size, 0, old_size * sizeof (rtx));
-      regno_reg_rtx = new1;
+void
+emit_status::ensure_regno_capacity ()
+{
+  int old_size = regno_pointer_align_length;
 
-      crtl->emit.regno_pointer_align_length = old_size * 2;
-    }
+  if (reg_rtx_no < old_size)
+    return;
 
-  val = gen_raw_REG (mode, reg_rtx_no);
-  regno_reg_rtx[reg_rtx_no++] = val;
-  return val;
+  int new_size = old_size * 2;
+  while (reg_rtx_no >= new_size)
+    new_size *= 2;
+
+  char *tmp = XRESIZEVEC (char, regno_pointer_align, new_size);
+  memset (tmp + old_size, 0, new_size - old_size);
+  regno_pointer_align = (unsigned char *) tmp;
+
+  rtx *new1 = GGC_RESIZEVEC (rtx, regno_reg_rtx, new_size);
+  memset (new1 + old_size, 0, (new_size - old_size) * sizeof (rtx));
+  regno_reg_rtx = new1;
+
+  crtl->emit.regno_pointer_align_length = new_size;
 }
 
 /* Return TRUE if REG is a PARM_DECL, FALSE otherwise.  */
@@ -5667,7 +5676,8 @@ init_emit (void)
   crtl->emit.regno_pointer_align
     = XCNEWVEC (unsigned char, crtl->emit.regno_pointer_align_length);
 
-  regno_reg_rtx = ggc_vec_alloc<rtx> (crtl->emit.regno_pointer_align_length);
+  regno_reg_rtx =
+    ggc_cleared_vec_alloc<rtx> (crtl->emit.regno_pointer_align_length);
 
   /* Put copies of all the hard registers into regno_reg_rtx.  */
   memcpy (regno_reg_rtx,
diff --git a/gcc/function.h b/gcc/function.h
index b564f45..cabffb9 100644
--- a/gcc/function.h
+++ b/gcc/function.h
@@ -34,6 +34,8 @@ struct GTY(()) sequence_stack {
 };
 \f
 struct GTY(()) emit_status {
+  void ensure_regno_capacity ();
+
   /* This is reset to LAST_VIRTUAL_REGISTER + 1 at the start of each function.
      After rtl generation, it is 1 plus the largest register number used.  */
   int x_reg_rtx_no;
-- 
1.8.5.3