On Fri, 1 Apr 2016, Bernd Schmidt wrote:
> On 04/01/2016 11:08 AM, Richard Biener wrote:
> > {
> > ! if (canon_true_dependence (s_info->mem,
> > ! GET_MODE (s_info->mem),
> > ! s_info->mem_addr,
> > ! mem, mem_addr))
> > {
> > s_info->rhs = NULL;
> > s_info->const_rhs = NULL;
> > --- 1609,1617 ----
> > the value of store_info. If it is, set the rhs to NULL to
> > keep it from being used to remove a load. */
> > {
> > ! if (canon_output_dependence (s_info->mem, true,
> > ! mem, GET_MODE (mem),
> > ! mem_addr))
> > {
> > s_info->rhs = NULL;
> > s_info->const_rhs = NULL;
>
> I think the patch is ok, but there is a comment in that function which
> references canon_true_dependence; that should also be fixed up.
Done, though I don't understand it at all ... if alias-set was supposed
to be zero for all cases we call canon_true_dependence then the issue
wouldn't have happened. Maybe there was times where passing mem_addr
== NULL_RTX to canon_true_dependence caused it to bail out?
Not sure how to adjust that comment now, maybe it would be valid
to simply remove the if (spill_alias_set) case and always use
the else case?
> Isn't the testcase invalid though? I thought accesses through char *
> pointers bypass aliasing rules, but accessing a char array through int *
> and long * pointers doesn't?
I have installed it as the following with adjusted testcase, if somebody
can shed some light on the odd comment I'll happily followup.
Richard.
2016-04-04 Richard Biener <rguent...@suse.de>
PR rtl-optimization/70484
* rtl.h (canon_output_dependence): Declare.
* alias.c (canon_output_dependence): New function.
* dse.c (record_store): Use canon_output_dependence rather
than canon_true_dependence.
* gcc.dg/torture/pr70484.c: New testcase.
Index: gcc/rtl.h
===================================================================
*** gcc/rtl.h (revision 234663)
--- gcc/rtl.h (working copy)
*************** extern int anti_dependence (const_rtx, c
*** 3652,3657 ****
--- 3652,3659 ----
extern int canon_anti_dependence (const_rtx, bool,
const_rtx, machine_mode, rtx);
extern int output_dependence (const_rtx, const_rtx);
+ extern int canon_output_dependence (const_rtx, bool,
+ const_rtx, machine_mode, rtx);
extern int may_alias_p (const_rtx, const_rtx);
extern void init_alias_target (void);
extern void init_alias_analysis (void);
Index: gcc/alias.c
===================================================================
*** gcc/alias.c (revision 234663)
--- gcc/alias.c (working copy)
*************** output_dependence (const_rtx mem, const_
*** 3057,3062 ****
--- 3057,3076 ----
/*mem_canonicalized=*/false,
/*x_canonicalized*/false, /*writep=*/true);
}
+
+ /* Likewise, but we already have a canonicalized MEM, and X_ADDR for X.
+ Also, consider X in X_MODE (which might be from an enclosing
+ STRICT_LOW_PART / ZERO_EXTRACT).
+ If MEM_CANONICALIZED is true, MEM is canonicalized. */
+
+ int
+ canon_output_dependence (const_rtx mem, bool mem_canonicalized,
+ const_rtx x, machine_mode x_mode, rtx x_addr)
+ {
+ return write_dependence_p (mem, x, x_mode, x_addr,
+ mem_canonicalized, /*x_canonicalized=*/true,
+ /*writep=*/true);
+ }
Index: gcc/dse.c
===================================================================
*** gcc/dse.c (revision 234663)
--- gcc/dse.c (working copy)
*************** record_store (rtx body, bb_info_t bb_inf
*** 1609,1618 ****
the value of store_info. If it is, set the rhs to NULL to
keep it from being used to remove a load. */
{
! if (canon_true_dependence (s_info->mem,
! GET_MODE (s_info->mem),
! s_info->mem_addr,
! mem, mem_addr))
{
s_info->rhs = NULL;
s_info->const_rhs = NULL;
--- 1609,1617 ----
the value of store_info. If it is, set the rhs to NULL to
keep it from being used to remove a load. */
{
! if (canon_output_dependence (s_info->mem, true,
! mem, GET_MODE (mem),
! mem_addr))
{
s_info->rhs = NULL;
s_info->const_rhs = NULL;
Index: gcc/testsuite/gcc.dg/torture/pr70484.c
===================================================================
*** gcc/testsuite/gcc.dg/torture/pr70484.c (revision 0)
--- gcc/testsuite/gcc.dg/torture/pr70484.c (revision 0)
***************
*** 0 ****
--- 1,19 ----
+ /* { dg-do run } */
+
+ extern void abort (void);
+
+ int __attribute__((noinline,noclone))
+ f(int *pi, long *pl)
+ {
+ *pi = 1;
+ *pl = 0;
+ return *(char *)pi;
+ }
+
+ int main()
+ {
+ union { long l; int i; } a;
+ if (f (&a.i, &a.l) != 0)
+ abort ();
+ return 0;
+ }
