tree-ssa-loop-ivopts.c (may_be_unaligned_p): Check the alignment of the variable…

tree-ssa-loop-ivopts.c (may_be_unaligned_p): Check the alignment of the variable part of the offset as well.

	* tree-ssa-loop-ivopts.c (may_be_unaligned_p): Check the alignment of
	the variable part of the offset as well.  Use highest_pow2_factor for
	all alignment checks.

From-SVN: r158948

gcc/ChangeLog

+2010-04-30  Eric Botcazou  <ebotcazou@adacore.com>
+
+	* tree-ssa-loop-ivopts.c (may_be_unaligned_p): Check the alignment of
+	the variable part of the offset as well.  Use highest_pow2_factor for
+	all alignment checks.
+
 2010-04-30  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/43879

gcc/testsuite/ChangeLog

+2010-04-30  DJ Delorie  <dj@redhat.com>
+
+	* gcc.c-torture/execute/20100430-1.c: New test.
+
 2010-04-30  Jason Merrill  <jason@redhat.com>
 
 	PR c++/43868

gcc/testsuite/gcc.c-torture/execute/20100430-1.c

+/* This used to generate unaligned accesses at -O2 because of IVOPTS.  */
+
+struct packed_struct
+{
+  struct packed_struct1
+  {
+    unsigned char cc11;
+    unsigned char cc12;
+  } __attribute__ ((packed)) pst1;
+  struct packed_struct2
+  {
+    unsigned char cc21;
+    unsigned char cc22;
+    unsigned short ss[104];
+    unsigned char cc23[13];
+  } __attribute__ ((packed)) pst2[4];
+} __attribute__ ((packed));
+
+typedef struct
+{
+  int ii;
+  struct packed_struct buf;
+} info_t;
+
+static unsigned short g;
+
+static void __attribute__((noinline))
+dummy (unsigned short s)
+{
+  g = s;
+}
+
+static int
+foo (info_t *info)
+{
+  int i, j;
+
+  for (i = 0; i < info->buf.pst1.cc11; i++)
+    for (j = 0; j < info->buf.pst2[i].cc22; j++)
+      dummy (info->buf.pst2[i].ss[j]);
+
+  return 0;
+}
+
+int main(void)
+{
+  info_t info;
+  info.buf.pst1.cc11 = 2;
+  info.buf.pst2[0].cc22 = info.buf.pst2[1].cc22 = 8;
+  return foo (&info);
+}

gcc/tree-ssa-loop-ivopts.c

@@ -1536,16 +1536,18 @@ may_be_unaligned_p (tree ref, tree step)
 
   if (mode != BLKmode)
     {
-      double_int mul;
-      tree al = build_int_cst (TREE_TYPE (step),
-			       GET_MODE_ALIGNMENT (mode) / BITS_PER_UNIT);
+      unsigned mode_align = GET_MODE_ALIGNMENT (mode);
 
-      if (base_align < GET_MODE_ALIGNMENT (mode)
-	  || bitpos % GET_MODE_ALIGNMENT (mode) != 0
-	  || bitpos % BITS_PER_UNIT != 0)
+      if (base_align < mode_align
+	  || (bitpos % mode_align) != 0
+	  || (bitpos % BITS_PER_UNIT) != 0)
 	return true;
 
-      if (!constant_multiple_of (step, al, &mul))
+      if (toffset
+	  && (highest_pow2_factor (toffset) * BITS_PER_UNIT) < mode_align)
+	return true;
+
+      if ((highest_pow2_factor (step) * BITS_PER_UNIT) < mode_align)
 	return true;
     }