2008-06-07 H.J. Lu <hongjiu.lu@intel.com>

	* defaults.h (MAX_STACK_ALIGNMENT): Update comments.
	(MAX_SUPPORTED_STACK_ALIGNMENT): New.

	* cfgexpand.c (get_decl_align_unit): Ignore alignment if it
	exceeds MAX_SUPPORTED_STACK_ALIGNMENT.
	* function.c (assign_stack_local_1): Likewise.
	(locate_and_pad_parm): Likewise.

	* doc/tm.texi (MAX_STACK_ALIGNMENT): Updated.


git-svn-id: https://gcc.gnu.org/svn/gcc/branches/stack@136524 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 43 insertions, 40 deletions

diff --git a/gcc/ChangeLog.stackalign b/gcc/ChangeLog.stackalign
index 11a91cf1ef2..c63c8abcca9 100644
--- a/gcc/ChangeLog.stackalign
+++ b/gcc/ChangeLog.stackalign
@@ -1,3 +1,15 @@
+2008-06-07  H.J. Lu  <hongjiu.lu@intel.com>
+
+	* defaults.h (MAX_STACK_ALIGNMENT): Update comments.
+	(MAX_SUPPORTED_STACK_ALIGNMENT): New.
+
+	* cfgexpand.c (get_decl_align_unit): Ignore alignment if it
+	exceeds MAX_SUPPORTED_STACK_ALIGNMENT.
+	* function.c (assign_stack_local_1): Likewise.
+	(locate_and_pad_parm): Likewise.
+
+	* doc/tm.texi (MAX_STACK_ALIGNMENT): Updated.
+
 2008-06-05  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* config/i386/i386.c (ix86_get_drap_rtx): Update comments.
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 5465ff22a45..be9996645ef 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -158,6 +158,9 @@ get_decl_align_unit (tree decl)
   align = DECL_ALIGN (decl);
   align = LOCAL_ALIGNMENT (TREE_TYPE (decl), align);
 
+  if (align > MAX_SUPPORTED_STACK_ALIGNMENT)
+    align = MAX_SUPPORTED_STACK_ALIGNMENT;
+
   if (SUPPORTS_STACK_ALIGNMENT)
     {
       if (crtl->stack_alignment_estimated < align)
@@ -166,11 +169,6 @@ get_decl_align_unit (tree decl)
           crtl->stack_alignment_estimated = align;
 	}
     }
-  else
-    {
-      if (align > PREFERRED_STACK_BOUNDARY)
-	align = PREFERRED_STACK_BOUNDARY;
-    }
 
   /* stack_alignment_needed > PREFERRED_STACK_BOUNDARY is permitted.
      So here we only make sure stack_alignment_needed >= align.  */
diff --git a/gcc/defaults.h b/gcc/defaults.h
index c86dc8b84a6..e6325685e5f 100644
--- a/gcc/defaults.h
+++ b/gcc/defaults.h
@@ -950,12 +950,17 @@ along with GCC; see the file COPYING3.  If not see
 #define OUTGOING_REG_PARM_STACK_SPACE(FNTYPE) 0
 #endif
 
-/* FIXME: The default should be PREFERRED_STACK_BOUNDARY.  But the fix
-   for PR 32893 indicates that we can only guarantee maximum stack
-   alignment on stack up to STACK_BOUNDARY, not PREFERRED_STACK_BOUNDARY,
-   if stack alignment isn't supported.  */
-#ifndef MAX_STACK_ALIGNMENT
+/* MAX_STACK_ALIGNMENT is the maximum stack alignment guaranteed by
+   the backend.  MAX_SUPPORTED_STACK_ALIGNMENT is the maximum best
+   effort stack alignment supported by the backend.  If the backend
+   supports stack alignment, MAX_SUPPORTED_STACK_ALIGNMENT and
+   MAX_STACK_ALIGNMENT are the same.  Otherwise, the incoming stack
+   boundary will limit the maximum guaranteed stack alignment.  */
+#ifdef MAX_STACK_ALIGNMENT
+#define MAX_SUPPORTED_STACK_ALIGNMENT MAX_STACK_ALIGNMENT
+#else
 #define MAX_STACK_ALIGNMENT STACK_BOUNDARY
+#define MAX_SUPPORTED_STACK_ALIGNMENT PREFERRED_STACK_BOUNDARY
 #endif
 
 #define SUPPORTS_STACK_ALIGNMENT (MAX_STACK_ALIGNMENT > STACK_BOUNDARY)
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index be51151d461..e165ab0d7cd 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -1125,7 +1125,7 @@ field alignment has not been set by the
 @end defmac
 
 @defmac MAX_STACK_ALIGNMENT
-Biggest stack alignment supported by the backend.  Use this macro
+Biggest stack alignment guaranteed by the backend.  Use this macro
 to specify the maximum alignment of a variable on stack.
 
 If not defined, the default value is @code{STACK_BOUNDARY}.
diff --git a/gcc/function.c b/gcc/function.c
index 7060c120de5..277dde88561 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -384,17 +384,19 @@ assign_stack_local_1 (enum machine_mode mode, HOST_WIDE_INT size,
   if (FRAME_GROWS_DOWNWARD)
     frame_offset -= size;
 
+  /* Ignore alignment if it exceeds MAX_SUPPORTED_STACK_ALIGNMENT.  */
+  if (alignment_in_bits >= MAX_SUPPORTED_STACK_ALIGNMENT)
+    {
+      alignment_in_bits = MAX_SUPPORTED_STACK_ALIGNMENT;
+      alignment = alignment_in_bits / BITS_PER_UNIT;
+    }
+
   if (SUPPORTS_STACK_ALIGNMENT)
     {
       if (crtl->stack_alignment_estimated < alignment_in_bits)
 	{
           if (!crtl->stack_realign_processed)
-	    {
-	      /* Can't exceed MAX_STACK_ALIGNMENT.  */
-	      if (alignment_in_bits >= MAX_STACK_ALIGNMENT)
-		alignment_in_bits = MAX_STACK_ALIGNMENT;
-	      crtl->stack_alignment_estimated = alignment_in_bits;
-	    }
+	    crtl->stack_alignment_estimated = alignment_in_bits;
           else
 	    {
 	      gcc_assert (!crtl->stack_realign_finalized);
@@ -413,16 +415,7 @@ assign_stack_local_1 (enum machine_mode mode, HOST_WIDE_INT size,
 	    }
 	}
     }
-  else
-    {
-      /* Ignore alignment we can't do with expected alignment of the
-	 boundary.  */
-      if (alignment * BITS_PER_UNIT > PREFERRED_STACK_BOUNDARY)
-	{
-	  alignment_in_bits = PREFERRED_STACK_BOUNDARY;
-	  alignment = PREFERRED_STACK_BOUNDARY / BITS_PER_UNIT;
-	}
-    }
+
   if (crtl->stack_alignment_needed < alignment_in_bits)
     crtl->stack_alignment_needed = alignment_in_bits;
   if (crtl->max_used_stack_slot_alignment < crtl->stack_alignment_needed)
@@ -3378,6 +3371,12 @@ locate_and_pad_parm (enum machine_mode passed_mode, tree type, int in_regs,
   locate->where_pad = where_pad;
   locate->boundary = boundary;
 
+  /* We can't exceed MAX_SUPPORTED_STACK_ALIGNMENT when we remember
+     if the outgoing parameter requires extra alignment on the calling
+     function side.  */
+  if (boundary >= MAX_SUPPORTED_STACK_ALIGNMENT)
+    boundary = MAX_SUPPORTED_STACK_ALIGNMENT;
+
   if (SUPPORTS_STACK_ALIGNMENT)
     {
       /* stack_alignment_estimated can't change after stack has been
@@ -3385,24 +3384,13 @@ locate_and_pad_parm (enum machine_mode passed_mode, tree type, int in_regs,
       if (crtl->stack_alignment_estimated < boundary)
         {
           if (!crtl->stack_realign_processed)
-	    {
-	      /* Can't exceed MAX_STACK_ALIGNMENT.  */
-	      if (boundary >= MAX_STACK_ALIGNMENT)
-		boundary = MAX_STACK_ALIGNMENT;
-	      crtl->stack_alignment_estimated = boundary;
-	    }
+	    crtl->stack_alignment_estimated = boundary;
 	  else
 	    gcc_assert (!crtl->stack_realign_finalized
 			&& crtl->stack_realign_needed);
 	}
     }
-  else
-    {
-      /* Remember if the outgoing parameter requires extra alignment on
-         the calling function side.  */
-      if (boundary > PREFERRED_STACK_BOUNDARY)
-        boundary = PREFERRED_STACK_BOUNDARY;
-    }
+
   if (crtl->stack_alignment_needed < boundary)
     crtl->stack_alignment_needed = boundary;
   if (crtl->max_used_stack_slot_alignment < crtl->stack_alignment_needed)