The following makes sure we fold the reads from string constants
created from folding memcpy (&foo, &string_cst[0], ...) to
eventually create similar code as if that memcpy folding wasn't
done (move-by-pieces).
Bootstrapped and tested on x86_64-unknown-linux-gnu.
Comments?
(yeah, those native_encode_expr improvement would be really nice,
eventually for a slightly different interface, native_encode_expr_part)
Thanks,
Richard.
2014-07-10 Richard Biener <rguent...@suse.de>
PR middle-end/61762
* gimple-fold.c (fold_string_cst_ctor_reference): Handle
all integral-typed reads.
* gcc.dg/pr61762.c: New testcase.
Index: gcc/gimple-fold.c
===================================================================
*** gcc/gimple-fold.c (revision 212356)
--- gcc/gimple-fold.c (working copy)
*************** fold_string_cst_ctor_reference (tree typ
*** 2891,2904 ****
unsigned HOST_WIDE_INT offset,
unsigned HOST_WIDE_INT size)
{
if (INTEGRAL_TYPE_P (type)
&& (TYPE_MODE (type)
== TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
&& (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
== MODE_INT)
&& GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1
! && size == BITS_PER_UNIT
! && !(offset % BITS_PER_UNIT))
{
offset /= BITS_PER_UNIT;
if (offset < (unsigned HOST_WIDE_INT) TREE_STRING_LENGTH (ctor))
--- 2891,2905 ----
unsigned HOST_WIDE_INT offset,
unsigned HOST_WIDE_INT size)
{
+ if (offset % BITS_PER_UNIT != 0)
+ return NULL_TREE;
if (INTEGRAL_TYPE_P (type)
&& (TYPE_MODE (type)
== TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
&& (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor))))
== MODE_INT)
&& GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1
! && size == BITS_PER_UNIT)
{
offset /= BITS_PER_UNIT;
if (offset < (unsigned HOST_WIDE_INT) TREE_STRING_LENGTH (ctor))
*************** fold_string_cst_ctor_reference (tree typ
*** 2913,2918 ****
--- 2914,2932 ----
in both cases. */
return build_zero_cst (type);
}
+ else if (size % BITS_PER_UNIT == 0
+ /* ??? Until native_encode_expr understands to only encode
+ a part of a (possibly very large) constant limit this
+ to sth larger than MAX_BITSIZE_MODE_ANY_MODE. After that
+ restriction is removed we can remove the case above. */
+ && offset + size < 128 * BITS_PER_UNIT
+ && BITS_PER_UNIT == 8)
+ {
+ unsigned char buf[128];
+ if (native_encode_expr (ctor, buf, sizeof (buf)) > 0)
+ return native_interpret_expr (type, &buf[offset / BITS_PER_UNIT],
+ size / BITS_PER_UNIT);
+ }
return NULL_TREE;
}
Index: gcc/testsuite/gcc.dg/pr61762.c
===================================================================
*** gcc/testsuite/gcc.dg/pr61762.c (revision 0)
--- gcc/testsuite/gcc.dg/pr61762.c (working copy)
***************
*** 0 ****
--- 1,19 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O -fdump-tree-ssa" } */
+
+ unsigned int f()
+ {
+ static const char string[] = "Private";
+
+ unsigned int priv;
+ __builtin_memcpy(&priv, &string[0], sizeof(priv));
+ return priv;
+ }
+
+ /* We should have removed the static string and simplified the
+ memcpy to a store from an integer constant. Gimplification
+ already performs the simplification but only after into-SSA
+ the unused local static is removed. */
+
+ /* { dg-final { scan-tree-dump-not "Private" "ssa" } } */
+ /* { dg-final { cleanup-tree-dump "ssa" } } */
