Revert "PR 34548"

This reverts commit 190051.

From-SVN: r190110

gcc/ChangeLog

+2012-08-02  Richard Henderson  <rth@redhat.com>
+
+	Revert:
+	PR 34548
+	* function.h (struct rtl_data): Add max_dynamic_stack_alignment.
+	* cfgexpand.c (gimple_expand_cfg): Initialise it.
+	* explow.c (allocate_dynamic_stack_space): Set it.  Simplify
+	alignment requirements given the known alignment of dynamic_offset.
+	* function.c (instantiate_virtual_regs): Align dtnamic_offset.
+
 2012-08-02  Kenneth Zadeck <zadeck@naturalbridge.com>
 
 	* cfgexpand.c (expand_debug_locations):  Encapsulate test for
@@ -391,15 +401,6 @@
 
 2012-08-01  Richard Henderson  <rth@redhat.com>
 
-	PR middle-end/34548
-	* function.h (struct rtl_data): Add max_dynamic_stack_alignment.
-	* cfgexpand.c (gimple_expand_cfg): Initialise it.
-	* explow.c (allocate_dynamic_stack_space): Set it.  Simplify
-	alignment requirements given the known alignment of dynamic_offset.
-	* function.c (instantiate_virtual_regs): Align dtnamic_offset.
-
-2012-08-01  Richard Henderson  <rth@redhat.com>
-
 	* expmed.h (NUM_MODE_PARTIAL_INT): New.
 	(NUM_MODE_VECTOR_INT, NUM_MODE_IP_INT, NUM_MODE_IPV_INT): New.
 	(struct expmed_op_cheap): Size one array on NUM_MODE_IPV_INT.

gcc/cfgexpand.c

@@ -4356,7 +4356,6 @@ gimple_expand_cfg (void)
   crtl->max_used_stack_slot_alignment = STACK_BOUNDARY;
   crtl->stack_alignment_estimated = 0;
   crtl->preferred_stack_boundary = STACK_BOUNDARY;
-  crtl->max_dynamic_stack_alignment = 0;
   cfun->cfg->max_jumptable_ents = 0;
 
   /* Resovle the function section.  Some targets, like ARM EABI rely on knowledge

gcc/explow.c

@@ -1173,6 +1173,7 @@ allocate_dynamic_stack_space (rtx size, unsigned size_align,
 {
   HOST_WIDE_INT stack_usage_size = -1;
   rtx final_label, final_target, target;
+  unsigned extra_align = 0;
   bool must_align;
 
   /* If we're asking for zero bytes, it doesn't matter what we point
@@ -1236,40 +1237,58 @@ allocate_dynamic_stack_space (rtx size, unsigned size_align,
   else if (size_align < BITS_PER_UNIT)
     size_align = BITS_PER_UNIT;
 
+  /* We can't attempt to minimize alignment necessary, because we don't
+     know the final value of preferred_stack_boundary yet while executing
+     this code.  */
+  if (crtl->preferred_stack_boundary < PREFERRED_STACK_BOUNDARY)
+    crtl->preferred_stack_boundary = PREFERRED_STACK_BOUNDARY;
+
   /* We will need to ensure that the address we return is aligned to
-     REQUIRED_ALIGN.  If that alignment is no larger than
-     PREFERRED_STACK_BOUNDARY, we can handle everything without an
-     explicit alignment.  */
-  if (required_align <= PREFERRED_STACK_BOUNDARY)
+     REQUIRED_ALIGN.  If STACK_DYNAMIC_OFFSET is defined, we don't
+     always know its final value at this point in the compilation (it
+     might depend on the size of the outgoing parameter lists, for
+     example), so we must align the value to be returned in that case.
+     (Note that STACK_DYNAMIC_OFFSET will have a default nonzero value if
+     STACK_POINTER_OFFSET or ACCUMULATE_OUTGOING_ARGS are defined).
+     We must also do an alignment operation on the returned value if
+     the stack pointer alignment is less strict than REQUIRED_ALIGN.
+
+     If we have to align, we must leave space in SIZE for the hole
+     that might result from the alignment operation.  */
+
+  must_align = (crtl->preferred_stack_boundary < required_align);
+  if (must_align)
     {
-      if (crtl->preferred_stack_boundary < required_align)
-	crtl->preferred_stack_boundary = required_align;
-      if (crtl->max_dynamic_stack_alignment < required_align)
-	crtl->max_dynamic_stack_alignment = required_align;
-      must_align = false;
+      if (required_align > PREFERRED_STACK_BOUNDARY)
+	extra_align = PREFERRED_STACK_BOUNDARY;
+      else if (required_align > STACK_BOUNDARY)
+	extra_align = STACK_BOUNDARY;
+      else
+	extra_align = BITS_PER_UNIT;
     }
-  else
-    {
-      unsigned extra, extra_align;
 
-      crtl->preferred_stack_boundary = PREFERRED_STACK_BOUNDARY;
-      crtl->max_dynamic_stack_alignment = PREFERRED_STACK_BOUNDARY;
+  /* ??? STACK_POINTER_OFFSET is always defined now.  */
+#if defined (STACK_DYNAMIC_OFFSET) || defined (STACK_POINTER_OFFSET)
+  must_align = true;
+  extra_align = BITS_PER_UNIT;
+#endif
 
-      extra_align = PREFERRED_STACK_BOUNDARY;
-      extra = (required_align - extra_align) / BITS_PER_UNIT;
+  if (must_align)
+    {
+      unsigned extra = (required_align - extra_align) / BITS_PER_UNIT;
 
       size = plus_constant (Pmode, size, extra);
       size = force_operand (size, NULL_RTX);
 
       if (flag_stack_usage_info)
 	stack_usage_size += extra;
+
       if (extra && size_align > extra_align)
 	size_align = extra_align;
-      must_align = true;
     }
 
   /* Round the size to a multiple of the required stack alignment.
-     Since the stack is presumed to be rounded before this allocation,
+     Since the stack if presumed to be rounded before this allocation,
      this will maintain the required alignment.
 
      If the stack grows downward, we could save an insn by subtracting

gcc/function.c

@@ -1892,14 +1892,7 @@ instantiate_virtual_regs (void)
   /* Compute the offsets to use for this function.  */
   in_arg_offset = FIRST_PARM_OFFSET (current_function_decl);
   var_offset = STARTING_FRAME_OFFSET;
-
   dynamic_offset = STACK_DYNAMIC_OFFSET (current_function_decl);
-  if (crtl->max_dynamic_stack_alignment)
-    {
-      int align = crtl->max_dynamic_stack_alignment / BITS_PER_UNIT;
-      dynamic_offset = (dynamic_offset + align - 1) & -align;
-    }
-
   out_arg_offset = STACK_POINTER_OFFSET;
 #ifdef FRAME_POINTER_CFA_OFFSET
   cfa_offset = FRAME_POINTER_CFA_OFFSET (current_function_decl);

gcc/function.h

@@ -347,10 +347,6 @@ struct GTY(()) rtl_data {
         local stack.  */
   unsigned int stack_alignment_estimated;
 
-  /* The (capped) maximum alignment of dynamic stack space, and thus the
-     required alignment of STACK_DYNAMIC_OFFSET.  */
-  unsigned int max_dynamic_stack_alignment;
-
   /* For reorg.  */
 
   /* If some insns can be deferred to the delay slots of the epilogue, the