Patch to align local PowerPC AltiVec arrays

[Wellander, Pat - Code Sourcery]

This is my first patch submittal so constructive criticism is appreciated.
This patch causes PowerPC AltiVec local stack arrays > 16 bytes to be 
aligned at 16 bytes.

2011-01-27  Pat Wellander <pwelland@codesourcery.com>

   * config/rs6000/rs6000.h (LOCAL_ALIGNMENT):
     AltiVec local arrays >= 16 bytes are now aligned to at least 16 bytes.

Index: config/rs6000/rs6000.h
===================================================================
--- config/rs6000/rs6000.h      (revision 171171)
+++ config/rs6000/rs6000.h      (working copy)
@@ -686,9 +686,16 @@

  /* A C expression to compute the alignment for a variables in the
     local store.  TYPE is the data type, and ALIGN is the alignment
-   that the object would ordinarily have.  */
-#define LOCAL_ALIGNMENT(TYPE, ALIGN)                           \
-  DATA_ALIGNMENT (TYPE, ALIGN)
+   that the object would ordinarily have.
+   Align most data using the DATA_ALIGNMENT macro but
+   align local Altivec arrays >= 16 bytes
+   to 16 bytes (128 bits).  The DATA_ALIGNMENT macro aligns
+   all char arrays (not struct fields) to 16 bytes. These
+   alignments don't appear to affect struct field arrays.  */
+#define LOCAL_ALIGNMENT(TYPE, ALIGN)                      \
+  (TARGET_ALTIVEC &&  (TREE_CODE (TYPE) == ARRAY_TYPE)    \
+ && tree_low_cst (TYPE_SIZE (TYPE), 1) >= 128 ? 128    \
+    : DATA_ALIGNMENT (TYPE, ALIGN))

  /* Alignment of field after `int : 0' in a structure.  */
  #define EMPTY_FIELD_BOUNDARY 32


2011-01-27  Pat Wellander <pwelland@codesourcery.com>

   * gcc.target/powerpc/altivec-34.c: Test AltiVec local array alignment

Index: gcc.target/powerpc/altivec-34.c
===================================================================
--- gcc.target/powerpc/altivec-34.c       (revision 0)
+++ gcc.target/powerpc/altivec-34.c       (revision 0)
@@ -0,0 +1,27 @@
+/* altivec-34.c */
+/* { dg-do run { target powerpc*-*-* } } */
+/* { dg-options "-O0 -maltivec" } */
+
+#include <stdlib.h>
+
+/* Align large local Altivec arrays at 128 bits */
+
+int main(void)
+{
+  long a1[5], a2[6], a3[4];
+  char c1[4], c2[17];
+  if (((long)(&a1[0])) & 0xf)
+    abort ();
+  if (((long)(&a2[0])) & 0xf)
+    abort ();
+  if (((long)(&a3[0])) & 0xf)
+    abort ();
+  if (((long)(&c1[0])) & 0xf)
+    abort ();
+  if (((long)(&c2[0])) & 0xf)
+    abort ();
+  exit (0);
+}
+
+