[PATCH] PR35258: Prevent CSE from generating overlapping memmoves
Andreas Krebbel
Andreas.Krebbel@de.ibm.com
Mon Feb 25 13:43:00 GMT 2008
Hi,
> It looks like you can use nonoverlapping_memrefs_p from alias.c
> instead of adding cse_mem_cannot_overlap_p?
I thought that one is only supposed to be used from within alias.c but
actually I don't see a reason for that.
So here is the patch.
Bootstrapped and regtested on x86_64, s390 and s390x.
OK for mainline and 4.3?
Bye,
-Andreas-
2008-02-25 Andreas Krebbel <krebbel1@de.ibm.com>
* cse.c (cse_insn): Avoid creation of overlapping MEMs.
* alias.c (nonoverlapping_memrefs_p): Export for use in other modules.
* alias.h (nonoverlapping_memrefs_p): Likewise.
2008-02-25 Andreas Krebbel <krebbel1@de.ibm.com>
* gcc.dg/pr35258.c: New testcase.
Index: gcc/cse.c
===================================================================
*** gcc/cse.c.orig 2008-02-22 10:46:18.000000000 +0100
--- gcc/cse.c 2008-02-25 09:15:34.000000000 +0100
*************** cse_insn (rtx insn, rtx libcall_insn)
*** 4753,4758 ****
--- 4753,4775 ----
src_elt_cost = MAX_COST;
}
+ /* Avoid creation of overlapping memory moves. */
+ if (MEM_P (trial) && MEM_P (SET_DEST (sets[i].rtl)))
+ {
+ rtx src, dest;
+
+ /* BLKmode moves are not handled by cse anyway. */
+ if (GET_MODE (trial) == BLKmode)
+ break;
+
+ src = canon_rtx (trial);
+ dest = canon_rtx (SET_DEST (sets[i].rtl));
+
+ if (!MEM_P (src) || !MEM_P (dest)
+ || !nonoverlapping_memrefs_p (src, dest))
+ break;
+ }
+
/* We don't normally have an insn matching (set (pc) (pc)), so
check for this separately here. We will delete such an
insn below.
Index: gcc/testsuite/gcc.dg/pr35258.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.dg/pr35258.c 2008-02-22 10:47:55.000000000 +0100
***************
*** 0 ****
--- 1,28 ----
+ /* { dg-do run } */
+ /* { dg-options "-O1" } */
+
+ extern void *memcpy (void *, const void *, __SIZE_TYPE__);
+ extern int memcmp (const void *, const void *, __SIZE_TYPE__);
+ extern void abort(void);
+
+ char str[9] = "1234";
+
+ void
+ bar (void)
+ {
+ unsigned int temp;
+ char *p = &str[2];
+
+ memcpy (&temp, &str[1], 4);
+ memcpy (p, &temp, 4);
+ str[1] = '.';
+ }
+
+ int main()
+ {
+ bar();
+ if (memcmp (str, "1.234", 5) != 0)
+ abort ();
+
+ return 0;
+ }
Index: gcc/alias.c
===================================================================
*** gcc/alias.c.orig 2007-10-26 10:35:40.000000000 +0200
--- gcc/alias.c 2008-02-25 09:11:51.000000000 +0100
*************** static int aliases_everything_p (const_r
*** 164,170 ****
static bool nonoverlapping_component_refs_p (const_tree, const_tree);
static tree decl_for_component_ref (tree);
static rtx adjust_offset_for_component_ref (tree, rtx);
- static int nonoverlapping_memrefs_p (const_rtx, const_rtx);
static int write_dependence_p (const_rtx, const_rtx, int);
static void memory_modified_1 (rtx, const_rtx, void *);
--- 164,169 ----
*************** adjust_offset_for_component_ref (tree x,
*** 1976,1982 ****
/* Return nonzero if we can determine the exprs corresponding to memrefs
X and Y and they do not overlap. */
! static int
nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
{
tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
--- 1975,1981 ----
/* Return nonzero if we can determine the exprs corresponding to memrefs
X and Y and they do not overlap. */
! int
nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
{
tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
Index: gcc/alias.h
===================================================================
*** gcc/alias.h.orig 2007-08-28 08:51:49.000000000 +0200
--- gcc/alias.h 2008-02-25 09:10:48.000000000 +0100
*************** extern alias_set_type get_varargs_alias_
*** 28,33 ****
--- 28,34 ----
extern alias_set_type get_frame_alias_set (void);
extern bool component_uses_parent_alias_set (const_tree);
extern bool alias_set_subset_of (alias_set_type, alias_set_type);
+ extern int nonoverlapping_memrefs_p (const_rtx, const_rtx);
/* This alias set can be used to force a memory to conflict with all
other memories, creating a barrier across which no memory reference
More information about the Gcc-patches
mailing list