[PR69123] fix handling of MEMs in VTA to avoid dataflow oscillation

The problem arises because we used to drop overwritten MEMs from loc
lists of VALUEs, but not of other onepart variables, and it just so
happens that, by doing so, block 6 in the testcase has no D#5 in its
output in the first pass, because the MEM holding its (previous) value
was correctly dropped from value 88:88, but gains it in the second
pass because D#5 has the MEM location incoming directly in its loc
list, rather than indirectly in a VALUE.

This incorrect binding enables other blocks to believe they have a
tentative binding for D#5 in some cycles, but others, still operating
on the early conclusion, believe there isn't, and they oscillate from
that.

Since we check for escaping MEMs in clobbers, we won't lose anything
relevant by dropping call-clobbered or overwritten MEMs in all onepart
variables, and this ensures the loc intersection operation in onepart
vars won't let a MEM through that wasn't present in earlier
iterations.

for  gcc/ChangeLog

	PR bootstrap/69123
	* var-tracking.c (drop_overlapping_mem_locs): Operate on all
	onepart vars.  Fix typo in comment.  Fix reversed condition in
	unshare test.
	(dataflow_set_remove_mem_locs): Operate on all onepart vars.

for gcc/testsuite/ChangeLog

	PR bootstrap/69123
	* g++.dg/pr69123.C: New.

From-SVN: r232218

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9b1c41b0c5120de79f891d822db16554c1f88920..71aac8e89c97cc1ab72b84967d4a616be7fe05d6 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,11 @@
 2016-01-11  Alexandre Oliva <aoliva@redhat.com>
 
+       PR bootstrap/69123
+       * var-tracking.c (drop_overlapping_mem_locs): Operate on all
+       onepart vars.  Fix typo in comment.  Fix reversed condition in
+       unshare test.
+       (dataflow_set_remove_mem_locs): Operate on all onepart vars.
+
        PR bootstrap/69123
        * var-tracking.c (dump_onepart_variable_differences): New.
        (dataflow_set_different): If a detailed dump is requested,

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index cabef26023e88cb897c3eb36f5351676204c86e8..7095b45d12efcbc52df173efa26640fbfe6323c6 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-01-11  Alexandre Oliva <aoliva@redhat.com>
+
+       PR bootstrap/69123
+       * g++.dg/pr69123.C: New.
+
 2016-01-11  Ilya Enkovich  <enkovich.gnu@gmail.com>
 
        PR target/69010

diff --git a/gcc/testsuite/g++.dg/pr69123.C b/gcc/testsuite/g++.dg/pr69123.C
new file mode 100644 (file)
index 0000000..0546e20
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr69123.C
@@ -0,0 +1,95 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -g" } */
+
+/* This was reduced from gcc/tree-vect-slp.c by H.J.Lu.  */
+
+struct xxx_def;
+typedef xxx_def *xxx;
+
+union rtxxx
+{
+  const char *rt_str;
+  xxx rt_xxx;
+};
+
+struct xxx_def {
+  union u {
+    rtxxx fld[1];
+  } u;
+};
+
+extern xxx bar (void);
+extern int foo1 (xxx);
+
+static inline xxx
+foo2 (xxx arg0, xxx arg1)
+{
+  xxx rt;
+  rt = bar ();
+  (((rt)->u.fld[0]).rt_xxx) = arg0;
+  (((rt)->u.fld[1]).rt_xxx) = arg1;
+  return rt;
+}
+
+static inline xxx
+foo4 (const char *arg0 )
+{
+  xxx rt;
+  rt = bar ();
+  (((rt)->u.fld[0]).rt_str) = arg0;
+  (((rt)->u.fld[1]).rt_xxx) = (xxx) 0;
+  return rt;
+}
+
+extern xxx foo5 (long);
+
+struct address_cost_data
+{
+  unsigned costs[2][2][2][2];
+};
+
+void
+get_address_cost (address_cost_data *data)
+{
+  unsigned acost;
+  long i;
+  long rat, off = 0;
+  unsigned sym_p, var_p, off_p, rat_p;
+  xxx addr, base;
+  xxx reg0, reg1;
+
+  reg1 = bar ();
+  addr = foo2 (reg1, (xxx) 0);
+  rat = 1;
+  acost = 0;
+  reg0 = bar ();
+  reg1 = bar ();
+
+  for (i = 0; i < 16; i++)
+    {
+      sym_p = i & 1;
+      var_p = (i >> 1) & 1;
+      off_p = (i >> 2) & 1;
+      rat_p = (i >> 3) & 1;
+
+      addr = reg0;
+      if (rat_p)
+       addr = foo2 (addr, foo5 (rat)) ;
+
+      if (var_p)
+       addr = foo2 (addr, reg1);
+
+      if (sym_p)
+       base = foo4 ("");
+      else if (off_p)
+       base = foo5 (off);
+      else
+       base = (xxx) 0;
+
+      if (base)
+       addr = foo2 (addr, base);
+
+      acost = foo1 (addr);
+      data->costs[sym_p][var_p][off_p][rat_p] = acost;
+    }
+}

diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c
index 023a73eddc33a99c3de4c13ab2ff351a33e11829..86183b3f0cd7cf7ad5e855125e6b0569edeecdc7 100644 (file)
--- a/gcc/var-tracking.c
+++ b/gcc/var-tracking.c
@@ -2224,7 +2224,7 @@ struct overlapping_mems
 };
 
 /* Remove all MEMs that overlap with COMS->LOC from the location list
-   of a hash table entry for a value.  COMS->ADDR must be a
+   of a hash table entry for a onepart variable.  COMS->ADDR must be a
    canonicalized form of COMS->LOC's address, and COMS->LOC must be
    canonicalized itself.  */
 
@@ -2235,7 +2235,7 @@ drop_overlapping_mem_locs (variable **slot, overlapping_mems *coms)
   rtx mloc = coms->loc, addr = coms->addr;
   variable *var = *slot;
 
-  if (var->onepart == ONEPART_VALUE)
+  if (var->onepart != NOT_ONEPART)
     {
       location_chain *loc, **locp;
       bool changed = false;
@@ -4682,11 +4682,11 @@ dataflow_set_preserve_mem_locs (variable **slot, dataflow_set *set)
        {
          for (loc = var->var_part[0].loc_chain; loc; loc = loc->next)
            {
-             /* We want to remove dying MEMs that doesn't refer to DECL.  */
+             /* We want to remove dying MEMs that don't refer to DECL.  */
              if (GET_CODE (loc->loc) == MEM
                  && (MEM_EXPR (loc->loc) != decl
                      || INT_MEM_OFFSET (loc->loc) != 0)
-                 && !mem_dies_at_call (loc->loc))
+                 && mem_dies_at_call (loc->loc))
                break;
              /* We want to move here MEMs that do refer to DECL.  */
              else if (GET_CODE (loc->loc) == VALUE
@@ -4769,14 +4769,14 @@ dataflow_set_preserve_mem_locs (variable **slot, dataflow_set *set)
 }
 
 /* Remove all MEMs from the location list of a hash table entry for a
-   value.  */
+   onepart variable.  */
 
 int
 dataflow_set_remove_mem_locs (variable **slot, dataflow_set *set)
 {
   variable *var = *slot;
 
-  if (var->onepart == ONEPART_VALUE)
+  if (var->onepart != NOT_ONEPART)
     {
       location_chain *loc, **locp;
       bool changed = false;