Re: [patch] Fix PR middle-end/78468

[Eric Botcazou]

> I'd say let's not have a middle ground - this stuff is sufficiently
> brain-twisting that I'd rather go back to a known working state. If
> there was an error in the previous patch, let's roll it back until we
> fully understand the situation.

Here's a revised version along these lines, OK for mainline after testing?


        PR middle-end/78468
        * emit-rtl.c (init_emit): Add ??? comment for problematic alignment
        settings of the virtual registers.

        Revert again
        2016-08-23  Dominik Vogt  <v...@linux.vnet.ibm.com>

        * explow.c (get_dynamic_stack_size): Take known alignment of stack
        pointer + STACK_DYNAMIC_OFFSET into account when calculating the size
        needed.


-- 
Eric Botcazou
Index: emit-rtl.c
===================================================================
--- emit-rtl.c	(revision 244917)
+++ emit-rtl.c	(working copy)
@@ -5725,10 +5725,13 @@ init_emit (void)
   REGNO_POINTER_ALIGN (HARD_FRAME_POINTER_REGNUM) = STACK_BOUNDARY;
   REGNO_POINTER_ALIGN (ARG_POINTER_REGNUM) = STACK_BOUNDARY;
 
+  /* ??? These are problematic (for example, 3 out of 4 are wrong on
+     32-bit SPARC and cannot be all fixed because of the ABI).  */
   REGNO_POINTER_ALIGN (VIRTUAL_INCOMING_ARGS_REGNUM) = STACK_BOUNDARY;
   REGNO_POINTER_ALIGN (VIRTUAL_STACK_VARS_REGNUM) = STACK_BOUNDARY;
   REGNO_POINTER_ALIGN (VIRTUAL_STACK_DYNAMIC_REGNUM) = STACK_BOUNDARY;
   REGNO_POINTER_ALIGN (VIRTUAL_OUTGOING_ARGS_REGNUM) = STACK_BOUNDARY;
+
   REGNO_POINTER_ALIGN (VIRTUAL_CFA_REGNUM) = BITS_PER_WORD;
 #endif
 
Index: explow.c
===================================================================
--- explow.c	(revision 244917)
+++ explow.c	(working copy)
@@ -1233,15 +1233,9 @@ get_dynamic_stack_size (rtx *psize, unsi
      example), so we must preventively align the value.  We leave space
      in SIZE for the hole that might result from the alignment operation.  */
 
-  unsigned known_align = REGNO_POINTER_ALIGN (VIRTUAL_STACK_DYNAMIC_REGNUM);
-  if (known_align == 0)
-    known_align = BITS_PER_UNIT;
-  if (required_align > known_align)
-    {
-      extra = (required_align - known_align) / BITS_PER_UNIT;
-      size = plus_constant (Pmode, size, extra);
-      size = force_operand (size, NULL_RTX);
-    }
+  extra = (required_align - BITS_PER_UNIT) / BITS_PER_UNIT;
+  size = plus_constant (Pmode, size, extra);
+  size = force_operand (size, NULL_RTX);
 
   if (flag_stack_usage_info && pstack_usage_size)
     *pstack_usage_size += extra;