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[PATCH 1/3] Misaligned top level MEM_REFs on LHS of assignments
- From: Martin Jambor <mjambor at suse dot cz>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Richard Guenther <rguenther at suse dot de>
- Date: Mon, 12 Mar 2012 15:09:02 +0100
- Subject: [PATCH 1/3] Misaligned top level MEM_REFs on LHS of assignments
- References: <20120312140901.004541946@virgil.suse.cz>
Hi,
this patch has not changed since I posted it the last time
(http://gcc.gnu.org/ml/gcc-patches/2012-02/msg01375.html) except for a
fixed formatting of a comment. It has been already approved by Richi
(http://gcc.gnu.org/ml/gcc-patches/2012-02/msg01389.html) and I intend
to commit it this week even if the other patches still undergo review.
Thanks,
Martin
2012-03-08 Martin Jambor <mjambor@suse.cz>
* expr.c (expand_assignment): Handle misaligned scalar writes to
memory through top-level MEM_REFs by calling store_bit_field.
* testsuite/gcc.dg/misaligned-expand-2.c: New test.
Index: src/gcc/expr.c
===================================================================
--- src.orig/gcc/expr.c
+++ src/gcc/expr.c
@@ -4593,10 +4593,12 @@ expand_assignment (tree to, tree from, b
if ((TREE_CODE (to) == MEM_REF
|| TREE_CODE (to) == TARGET_MEM_REF)
&& mode != BLKmode
+ && !mem_ref_refers_to_non_mem_p (to)
&& ((align = get_object_or_type_alignment (to))
< GET_MODE_ALIGNMENT (mode))
- && ((icode = optab_handler (movmisalign_optab, mode))
- != CODE_FOR_nothing))
+ && (((icode = optab_handler (movmisalign_optab, mode))
+ != CODE_FOR_nothing)
+ || SLOW_UNALIGNED_ACCESS (mode, align)))
{
addr_space_t as
= TYPE_ADDR_SPACE (TREE_TYPE (TREE_TYPE (TREE_OPERAND (to, 0))));
@@ -4639,11 +4641,17 @@ expand_assignment (tree to, tree from, b
if (TREE_THIS_VOLATILE (to))
MEM_VOLATILE_P (mem) = 1;
- create_fixed_operand (&ops[0], mem);
- create_input_operand (&ops[1], reg, mode);
- /* The movmisalign<mode> pattern cannot fail, else the assignment would
- silently be omitted. */
- expand_insn (icode, 2, ops);
+ if (icode != CODE_FOR_nothing)
+ {
+ create_fixed_operand (&ops[0], mem);
+ create_input_operand (&ops[1], reg, mode);
+ /* The movmisalign<mode> pattern cannot fail, else the assignment
+ would silently be omitted. */
+ expand_insn (icode, 2, ops);
+ }
+ else
+ store_bit_field (mem, GET_MODE_BITSIZE (mode),
+ 0, 0, 0, mode, reg);
return;
}
Index: src/gcc/testsuite/gcc.dg/misaligned-expand-2.c
===================================================================
--- /dev/null
+++ src/gcc/testsuite/gcc.dg/misaligned-expand-2.c
@@ -0,0 +1,42 @@
+/* Test that expand can generate correct stores to misaligned data even on
+ strict alignment platforms. */
+
+/* { dg-do run } */
+/* { dg-options "-O0" } */
+
+extern void abort ();
+
+typedef unsigned int myint __attribute__((aligned(1)));
+
+void
+foo (myint *p, unsigned int i)
+{
+ *p = i;
+}
+
+#define cst 0xdeadbeef
+#define NUM 8
+
+struct blah
+{
+ char c;
+ myint i[NUM];
+};
+
+struct blah g;
+
+#define cst 0xdeadbeef
+
+int
+main (int argc, char **argv)
+{
+ int k;
+
+ for (k = 0; k < NUM; k++)
+ {
+ foo (&g.i[k], cst);
+ if (g.i[k] != cst)
+ abort ();
+ }
+ return 0;
+}