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Re: [RFA][PATCH] Minor fix to aliasing machinery
- From: Marc Glisse <marc dot glisse at inria dot fr>
- To: Richard Biener <richard dot guenther at gmail dot com>
- Cc: Jeff Law <law at redhat dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Sat, 9 Nov 2013 00:18:33 +0100 (CET)
- Subject: Re: [RFA][PATCH] Minor fix to aliasing machinery
- Authentication-results: sourceware.org; auth=none
- References: <52702A5D dot 6030101 at redhat dot com> <alpine dot DEB dot 2 dot 10 dot 1310292254130 dot 4124 at laptop-mg dot saclay dot inria dot fr> <CAFiYyc1KVe0y0n2CwAwdV0hKG-RpPKXEE73gcanmP4mjGpxCYg at mail dot gmail dot com> <alpine dot DEB dot 2 dot 02 dot 1310301703210 dot 3709 at stedding dot saclay dot inria dot fr> <alpine dot DEB dot 2 dot 02 dot 1311061308080 dot 20046 at stedding dot saclay dot inria dot fr> <CAFiYyc3Sa+ej51m2GrNVVcVjh1B3XskS=boo3fKamdG8odXyiA at mail dot gmail dot com> <alpine dot DEB dot 2 dot 10 dot 1311061455590 dot 16233 at stedding dot saclay dot inria dot fr> <CAFiYyc3fQTBCBwnjO==-6+=guthhCcMbxYS3RJLQS2XaRP5fPQ at mail dot gmail dot com>
On Wed, 6 Nov 2013, Richard Biener wrote:
So the only thing that remains is the mem_ref_offset thing and yes, I guess
I'd prefer to use double-ints because we deal with bit offsets in the end.
Here it is (bootstrap+testsuite on x86_64-unknown-linux-gnu). It feels
rather artificial to do this small bit of computation with double_int
when so much else assumes HWI is enough, but why not...
2013-11-09 Marc Glisse <marc.glisse@inria.fr>
Jeff Law <law@redhat.com>
gcc/
* tree-ssa-alias.c (stmt_kills_ref_p_1): Use
ao_ref_init_from_ptr_and_size for builtins.
gcc/testsuite/
* gcc.dg/tree-ssa/alias-27.c: New testcase.
--
Marc GlisseIndex: gcc/testsuite/gcc.dg/tree-ssa/alias-27.c
===================================================================
--- gcc/testsuite/gcc.dg/tree-ssa/alias-27.c (revision 0)
+++ gcc/testsuite/gcc.dg/tree-ssa/alias-27.c (working copy)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
+
+void f (long *p) {
+ *p = 42;
+ p[4] = 42;
+ __builtin_memset (p, 0, 100);
+}
+
+/* { dg-final { scan-tree-dump-not "= 42" "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Property changes on: gcc/testsuite/gcc.dg/tree-ssa/alias-27.c
___________________________________________________________________
Added: svn:keywords
## -0,0 +1 ##
+Author Date Id Revision URL
\ No newline at end of property
Added: svn:eol-style
## -0,0 +1 ##
+native
\ No newline at end of property
Index: gcc/tree-ssa-alias.c
===================================================================
--- gcc/tree-ssa-alias.c (revision 204608)
+++ gcc/tree-ssa-alias.c (working copy)
@@ -2001,23 +2001,24 @@ stmt_may_clobber_ref_p (gimple stmt, tre
return stmt_may_clobber_ref_p_1 (stmt, &r);
}
/* If STMT kills the memory reference REF return true, otherwise
return false. */
static bool
stmt_kills_ref_p_1 (gimple stmt, ao_ref *ref)
{
/* For a must-alias check we need to be able to constrain
- the access properly. */
- ao_ref_base (ref);
- if (ref->max_size == -1)
+ the access properly.
+ FIXME: except for BUILTIN_FREE. */
+ if (!ao_ref_base (ref)
+ || ref->max_size == -1)
return false;
if (gimple_has_lhs (stmt)
&& TREE_CODE (gimple_get_lhs (stmt)) != SSA_NAME
/* The assignment is not necessarily carried out if it can throw
and we can catch it in the current function where we could inspect
the previous value.
??? We only need to care about the RHS throwing. For aggregate
assignments or similar calls and non-call exceptions the LHS
might throw as well. */
@@ -2090,37 +2091,47 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref
case BUILT_IN_MEMPCPY:
case BUILT_IN_MEMMOVE:
case BUILT_IN_MEMSET:
case BUILT_IN_MEMCPY_CHK:
case BUILT_IN_MEMPCPY_CHK:
case BUILT_IN_MEMMOVE_CHK:
case BUILT_IN_MEMSET_CHK:
{
tree dest = gimple_call_arg (stmt, 0);
tree len = gimple_call_arg (stmt, 2);
- tree base = NULL_TREE;
- HOST_WIDE_INT offset = 0;
if (!host_integerp (len, 0))
return false;
- if (TREE_CODE (dest) == ADDR_EXPR)
- base = get_addr_base_and_unit_offset (TREE_OPERAND (dest, 0),
- &offset);
- else if (TREE_CODE (dest) == SSA_NAME)
- base = dest;
- if (base
- && base == ao_ref_base (ref))
+ tree rbase = ref->base;
+ double_int roffset = double_int::from_shwi (ref->offset);
+ ao_ref dref;
+ ao_ref_init_from_ptr_and_size (&dref, dest, len);
+ tree base = ao_ref_base (&dref);
+ double_int offset = double_int::from_shwi (dref.offset);
+ double_int bpu = double_int::from_uhwi (BITS_PER_UNIT);
+ if (!base || dref.size == -1)
+ return false;
+ if (TREE_CODE (base) == MEM_REF)
+ {
+ if (TREE_CODE (rbase) != MEM_REF)
+ return false;
+ // Compare pointers.
+ offset += bpu * mem_ref_offset (base);
+ roffset += bpu * mem_ref_offset (rbase);
+ base = TREE_OPERAND (base, 0);
+ rbase = TREE_OPERAND (rbase, 0);
+ }
+ if (base == rbase)
{
- HOST_WIDE_INT size = TREE_INT_CST_LOW (len);
- if (offset <= ref->offset / BITS_PER_UNIT
- && (offset + size
- >= ((ref->offset + ref->max_size + BITS_PER_UNIT - 1)
- / BITS_PER_UNIT)))
+ double_int size = bpu * tree_to_double_int (len);
+ double_int rsize = double_int::from_uhwi (ref->max_size);
+ if (offset.sle (roffset)
+ && (roffset + rsize).sle (offset + size))
return true;
}
break;
}
case BUILT_IN_VA_END:
{
tree ptr = gimple_call_arg (stmt, 0);
if (TREE_CODE (ptr) == ADDR_EXPR)
{