* tree.h (DECL_OFFSET_ALIGN): Make the off_align field of

the tree structure an exponent rather than an explicit alignment
so it doesn't overflow.
(SET_DECL_OFFSET_ALIGN): New macro.
* stor-layout.c (place_union_field): Use SET_DECL_OFFSET_ALIGN
rather than DECL_OFFSET_ALIGN.
(place_field): Likewise.
* expmed.c (store_bit_field): Abort on align==0 to avoid
antisocial machine behaviour.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@35659 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 28 insertions, 4 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 402fe228aec..cc284f2e39e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,15 @@
+2000-05-13  Geoffrey Keating  <geoffk@cygnus.com>
+
+	* tree.h (DECL_OFFSET_ALIGN): Make the off_align field of
+	the tree structure an exponent rather than an explicit alignment
+	so it doesn't overflow.
+	(SET_DECL_OFFSET_ALIGN): New macro.
+	* stor-layout.c (place_union_field): Use SET_DECL_OFFSET_ALIGN
+	rather than DECL_OFFSET_ALIGN.
+	(place_field): Likewise.
+	* expmed.c (store_bit_field): Abort on align==0 to avoid
+	antisocial machine behaviour.
+
 2000-08-12  Richard Henderson  <rth@cygnus.com>
 
 	* sibcall.c (uses_addressof): Accept both addressof and
diff --git a/gcc/expmed.c b/gcc/expmed.c
index e9210a680a3..606333fdbe3 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -245,6 +245,11 @@ store_bit_field (str_rtx, bitsize, bitnum, fieldmode, value, align, total_size)
   insv_bitsize = GET_MODE_BITSIZE (op_mode);
 #endif
 
+  /* It is wrong to have align==0, since every object is aligned at
+     least at a bit boundary.  This usually means a bug elsewhere.  */
+  if (align == 0)
+    abort ();
+
   /* Discount the part of the structure before the desired byte.
      We need to know how many bytes are safe to reference after it.  */
   if (total_size >= 0)
diff --git a/gcc/stor-layout.c b/gcc/stor-layout.c
index 12162e7f14b..159e2a8551f 100644
--- a/gcc/stor-layout.c
+++ b/gcc/stor-layout.c
@@ -584,7 +584,7 @@ place_union_field (rli, field)
   
   DECL_FIELD_OFFSET (field) = size_zero_node;
   DECL_FIELD_BIT_OFFSET (field) = bitsize_zero_node;
-  DECL_OFFSET_ALIGN (field) = BIGGEST_ALIGNMENT;
+  SET_DECL_OFFSET_ALIGN (field, BIGGEST_ALIGNMENT);
 
   desired_align = DECL_ALIGN (field);
 
@@ -859,7 +859,7 @@ place_field (rli, field)
   normalize_rli (rli);
   DECL_FIELD_OFFSET (field) = rli->offset;
   DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
-  DECL_OFFSET_ALIGN (field) = rli->offset_align;
+  SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
 
   /* If this field ended up more aligned than we thought it would be (we
      approximate this by seeing if its position changed), lay out the field
diff --git a/gcc/tree.h b/gcc/tree.h
index 781ef436fc0..e428a8a3864 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1308,8 +1308,15 @@ struct tree_type
 #define DECL_SIZE_UNIT(NODE) (DECL_CHECK (NODE)->decl.size_unit)
 /* Holds the alignment required for the datum.  */
 #define DECL_ALIGN(NODE) (DECL_CHECK (NODE)->decl.u1.a.align)
-/* For FIELD_DECLs, holds the alignment that DECL_FIELD_OFFSET has.  */
-#define DECL_OFFSET_ALIGN(NODE) (FIELD_DECL_CHECK (NODE)->decl.u1.a.off_align)
+/* For FIELD_DECLs, off_align holds the number of low-order bits of
+   DECL_FIELD_OFFSET which are known to be always zero.
+   DECL_OFFSET_ALIGN thus returns the alignment that DECL_FIELD_OFFSET
+   has.  */
+#define DECL_OFFSET_ALIGN(NODE) \
+  (((unsigned HOST_WIDE_INT)1) << FIELD_DECL_CHECK (NODE)->decl.u1.a.off_align)
+/* Specify that DECL_ALIGN(NODE) is a multiple of X.  */
+#define SET_DECL_OFFSET_ALIGN(NODE, X) \
+  (FIELD_DECL_CHECK (NODE)->decl.u1.a.off_align	= exact_log2 ((X) & -(X)))
 /* 1 if the alignment for this type was requested by "aligned" attribute,
    0 if it is the default for this type.  */
 #define DECL_USER_ALIGN(NODE) (DECL_CHECK (NODE)->decl.user_align)