cselib: Don't consider SP_DERIVED_VALUE_P values as useless [PR94468]

The following testcase ICEs, because at one point we see the
SP_DERIVED_VALUE_P VALUE as useless (not PRESERVED_VALUE_P and no locs)
and so expect it to be discarded as useless.  But, later on we
are adding some new VALUE that is equivalent to it, and when adding
the equivalency that that new VALUE is equal to this SP_DERIVED_VALUE_P,
new_elt_loc_list has code for VALUE canonicalization and reverses addition
if uid is smaller, and at that point a new loc is added to the
SP_DERIVED_VALUE_P VALUE and it isn't discarded as useless anymore.
Now, I think we don't want to discard the SP_DERIVED_VALUE_P values
even if they have no locs, because they still have the special behaviour
that they then force other new VALUEs to be canonicalized against them,
which is what this patch implements.  I've not set PRESERVED_VALUE_P
on the SP_DERIVED_VALUE_P at the creation time, because whether a VALUE
is preserved or not is something that affects var-tracking decisions quite a
lot and we shouldn't set it blindly on other VALUEs.

Or, to avoid the repetitive code, should I introduce
static bool
cselib_useless_value_p (cselib_val *v)
{
  return (v->locs == 0
	  && !PRESERVED_VALUE_P (v->val_rtx)
	  && !SP_DERIVED_VALUE_P (v->val_rtx)));
}
predicate and use it in those 6 spots?

2020-04-04  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/94468
	* cselib.c (references_value_p): Formatting fix.
	(cselib_useless_value_p): New function.
	(discard_useless_locs, discard_useless_values,
	cselib_invalidate_regno_val, cselib_invalidate_mem,
	cselib_record_set): Use it instead of
	v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx).

	* g++.dg/opt/pr94468.C: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fdb685a99d1f42d7a3ca4435977772bb1f0be4a0..0221945fe6cc683f40208fa7b226d92fc20ad2ef 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,13 @@
 2020-04-04  Jakub Jelinek  <jakub@redhat.com>
 
+       PR rtl-optimization/94468
+       * cselib.c (references_value_p): Formatting fix.
+       (cselib_useless_value_p): New function.
+       (discard_useless_locs, discard_useless_values,
+       cselib_invalidate_regno_val, cselib_invalidate_mem,
+       cselib_record_set): Use it instead of
+       v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx).
+
        PR debug/94441
        * tree-iterator.h (expr_single): Declare.
        * tree-iterator.c (expr_single): New function.

diff --git a/gcc/cselib.c b/gcc/cselib.c
index 507898ed1e8361edbdaefb6780b50ab7d10f8c14..256bd7852070b0d7ab8224ffa58bd451b144a9f6 100644 (file)
--- a/gcc/cselib.c
+++ b/gcc/cselib.c
@@ -629,8 +629,8 @@ references_value_p (const_rtx x, int only_useless)
   int i, j;
 
   if (GET_CODE (x) == VALUE
-      && (! only_useless ||
-         (CSELIB_VAL_PTR (x)->locs == 0 && !PRESERVED_VALUE_P (x))))
+      && (! only_useless
+         || (CSELIB_VAL_PTR (x)->locs == 0 && !PRESERVED_VALUE_P (x))))
     return 1;
 
   for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
@@ -646,6 +646,16 @@ references_value_p (const_rtx x, int only_useless)
   return 0;
 }
 
+/* Return true if V is a useless VALUE and can be discarded as such.  */
+
+static bool
+cselib_useless_value_p (cselib_val *v)
+{
+  return (v->locs == 0
+         && !PRESERVED_VALUE_P (v->val_rtx)
+         && !SP_DERIVED_VALUE_P (v->val_rtx));
+}
+
 /* For all locations found in X, delete locations that reference useless
    values (i.e. values without any location).  Called through
    htab_traverse.  */
@@ -666,7 +676,7 @@ discard_useless_locs (cselib_val **x, void *info ATTRIBUTE_UNUSED)
        p = &(*p)->next;
     }
 
-  if (had_locs && v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx))
+  if (had_locs && cselib_useless_value_p (v))
     {
       if (setting_insn && DEBUG_INSN_P (setting_insn))
        n_useless_debug_values++;
@@ -684,7 +694,7 @@ discard_useless_values (cselib_val **x, void *info ATTRIBUTE_UNUSED)
 {
   cselib_val *v = *x;
 
-  if (v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx))
+  if (v->locs == 0 && cselib_useless_value_p (v))
     {
       if (cselib_discard_hook)
        cselib_discard_hook (v);
@@ -2370,7 +2380,7 @@ cselib_invalidate_regno_val (unsigned int regno, struct elt_list **l)
        }
     }
 
-  if (had_locs && v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx))
+  if (had_locs && cselib_useless_value_p (v))
     {
       if (setting_insn && DEBUG_INSN_P (setting_insn))
        n_useless_debug_values++;
@@ -2515,7 +2525,7 @@ cselib_invalidate_mem (rtx mem_rtx)
          unchain_one_elt_loc_list (p);
        }
 
-      if (had_locs && v->locs == 0 && !PRESERVED_VALUE_P (v->val_rtx))
+      if (had_locs && cselib_useless_value_p (v))
        {
          if (setting_insn && DEBUG_INSN_P (setting_insn))
            n_useless_debug_values++;
@@ -2593,14 +2603,14 @@ cselib_record_set (rtx dest, cselib_val *src_elt, cselib_val *dest_addr_elt)
          REG_VALUES (dreg)->elt = src_elt;
        }
 
-      if (src_elt->locs == 0 && !PRESERVED_VALUE_P (src_elt->val_rtx))
+      if (cselib_useless_value_p (src_elt))
        n_useless_values--;
       new_elt_loc_list (src_elt, dest);
     }
   else if (MEM_P (dest) && dest_addr_elt != 0
           && cselib_record_memory)
     {
-      if (src_elt->locs == 0 && !PRESERVED_VALUE_P (src_elt->val_rtx))
+      if (cselib_useless_value_p (src_elt))
        n_useless_values--;
       add_mem_for_addr (dest_addr_elt, src_elt, dest);
     }

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index c08bc0d68f74232a51fdfa07e6cd62709f6e2e5e..427266a877f99d75f5c32aadef37385a8e98a700 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,8 @@
 2020-04-04  Jakub Jelinek  <jakub@redhat.com>
 
+       PR rtl-optimization/94468
+       * g++.dg/opt/pr94468.C: New test.
+
        PR debug/94441
        * g++.dg/opt/pr94441.C: New test.
 

diff --git a/gcc/testsuite/g++.dg/opt/pr94468.C b/gcc/testsuite/g++.dg/opt/pr94468.C
new file mode 100644 (file)
index 0000000..bd3f0b5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr94468.C
@@ -0,0 +1,57 @@
+// PR rtl-optimization/94468
+// { dg-do compile { target c++11 } }
+// { dg-options "-O2" }
+// { dg-additional-options "-fPIC" { target fpic } }
+
+bool a();
+enum b {};
+class c;
+template <typename> struct d;
+template <class e, typename g, typename... h> struct d<g (e::*)(h...)> {
+  typedef e i;
+};
+struct j { j(void(int, j *, c *, void **, bool *)) {} };
+template <typename l> struct m : public j {
+  l ab;
+  static void ac(int, j *, c *, void **, bool *);
+  m(l f) : j(ac), ab(f) {}
+};
+b ad;
+struct c {
+  template <typename n, typename o>
+  void ae(typename d<n>::i *p, n af, typename d<o>::i *ag, o ah) {
+    ai(p, &af, ag, &ah, new m<o>(ah), ad, &d<n>::i::aj);
+  }
+  void ai(c *, void *, c *, void *, j *, b, int *);
+};
+struct r : public c { static int aj; void t(); };
+struct al : public c {
+  static int aj;
+  void am();
+  void ao();
+  void ap();
+};
+struct aq { aq(const int &, const int & = int()); };
+struct ar : public c { ~ar(); };
+struct as : public ar {
+  as();
+  void at();
+  void au();
+  void av();
+};
+struct u : public c { void ax(); };
+struct ay { int az(); };
+struct ba : public c { static int aj; void bb(); };
+struct bc : public al { bc() { if (a()) am(); } };
+as::as() {
+  al *bd = new bc;
+  ae(bd, &al::ao, this, &as::au);
+  ae(bd, &al::ap, this, &as::av);
+  r be;
+  u bf;
+  ae(&be, &r::t, &bf, &u::ax);
+  c bg = *bd;
+  ae(static_cast<ba *>(&bg), &ba::bb, this, &as::at);
+  ay bh;
+  aq am(bh.az());
+}