This makes ao_ref_from_mem less conservative if either MEM_OFFSET or
MEM_SIZE is not set. From other alias.c code and
set_mem_attributes_minus_bitpos one has to conclude that MEM_EXPR
is always conservatively correct (it only can cover a larger memory
area) and the MEM_OFFSET / MEM_SIZE pair can refine it. Thus,
we can make ao_ref_from_mem less conservative when, for example,
faced with variable array accesses which set_mem_attributes_minus_bitpos
ends up representing with an unknown MEM_OFFSET.
Bootstrap and regtest running on x86_64-unknown-linux-gnu.
Richard.
2012-06-11 Richard Guenther rguent...@suse.de
* emit-rtl.c (set_mem_attributes_minus_bitpos): Remove dead code.
* alias.c (ao_ref_from_mem): MEM_EXPR is conservative, MEM_OFFSET
and MEM_SIZE only refines it. Reflect that and be less conservative
if either of the latter is not known.
Index: gcc/emit-rtl.c
===
*** gcc/emit-rtl.c (revision 188384)
--- gcc/emit-rtl.c (working copy)
*** set_mem_attributes_minus_bitpos (rtx ref
*** 1838,1852
/* ??? Any reason the field size would be different than
the size we got from the type? */
}
-
- /* If this is an indirect reference, record it. */
- else if (TREE_CODE (t) == MEM_REF)
- {
- attrs.expr = t;
- attrs.offset_known_p = true;
- attrs.offset = 0;
- apply_bitpos = bitpos;
- }
}
/* If this is an indirect reference, record it. */
--- 1838,1843
Index: gcc/alias.c
===
*** gcc/alias.c (revision 188384)
--- gcc/alias.c (working copy)
*** ao_ref_from_mem (ao_ref *ref, const_rtx
*** 326,342
ref-ref_alias_set = MEM_ALIAS_SET (mem);
! /* If MEM_OFFSET or MEM_SIZE are unknown we have to punt.
! Keep points-to related information though. */
if (!MEM_OFFSET_KNOWN_P (mem)
|| !MEM_SIZE_KNOWN_P (mem))
! {
! ref-ref = NULL_TREE;
! ref-offset = 0;
! ref-size = -1;
! ref-max_size = -1;
! return true;
! }
/* If the base decl is a parameter we can have negative MEM_OFFSET in
case of promoted subregs on bigendian targets. Trust the MEM_EXPR
--- 326,336
ref-ref_alias_set = MEM_ALIAS_SET (mem);
! /* If MEM_OFFSET or MEM_SIZE are unknown what we got from MEM_EXPR
! is conservative, so trust it. */
if (!MEM_OFFSET_KNOWN_P (mem)
|| !MEM_SIZE_KNOWN_P (mem))
! return true;
/* If the base decl is a parameter we can have negative MEM_OFFSET in
case of promoted subregs on bigendian targets. Trust the MEM_EXPR
*** ao_ref_from_mem (ao_ref *ref, const_rtx
*** 345,350
--- 339,347
(MEM_SIZE (mem) + MEM_OFFSET (mem)) * BITS_PER_UNIT == ref-size)
return true;
+ /* Otherwise continue and refine size and offset we got from analyzing
+ MEM_EXPR by using MEM_SIZE and MEM_OFFSET. */
+
ref-offset += MEM_OFFSET (mem) * BITS_PER_UNIT;
ref-size = MEM_SIZE (mem) * BITS_PER_UNIT;
