re PR middle-end/12392 (very long optimized compile)

2016-03-30  Michael Matz  <matz@suse.de>
	Richard Biener  <rguenther@suse.de>

	PR ipa/12392
	* ipa-polymorphic-call.c (struct type_change_info): Change
	speculative to an unsigned allowing to limit the work we do.
	(csftc_abort_walking_p): New inline function..
	(check_stmt_for_type_change): Limit the number of may-defs
	skipped for speculative devirtualization to
	max-speculative-devirt-maydefs.
	* params.def (max-speculative-devirt-maydefs): New param.
	* doc/invoke.texi (--param max-speculative-devirt-maydefs): Document.

Co-Authored-By: Richard Biener <rguenther@suse.de>
From-SVN: r234546

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 40fddc4007e5ae7642d4f320323b538b83891fb8..f09c0a0263881fc0668375b5cea1ce5c362b09b9 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2016-03-30  Michael Matz  <matz@suse.de>
+       Richard Biener  <rguenther@suse.de>
+
+       PR ipa/12392
+       * ipa-polymorphic-call.c (struct type_change_info): Change
+       speculative to an unsigned allowing to limit the work we do.
+       (csftc_abort_walking_p): New inline function..
+       (check_stmt_for_type_change): Limit the number of may-defs
+       skipped for speculative devirtualization to
+       max-speculative-devirt-maydefs.
+       * params.def (max-speculative-devirt-maydefs): New param.
+       * doc/invoke.texi (--param max-speculative-devirt-maydefs): Document.
+
 2016-03-30  Mike Stump  <mrs@gcc.gnu.org>
 
        PR target/63890

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index ed1ad6214b276176113e55f6499478466eecd60c..e9763d44d8d7aa6a64821a4b1811e55025aaaa4e 100644 (file)
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -9601,6 +9601,11 @@ Enable emission of special debug stores within HSA kernels which are
 then read and reported by libgomp plugin.  Generation of these stores
 is disabled by default, use @option{--param hsa-gen-debug-stores=1} to
 enable it.
+
+@item max-speculative-devirt-maydefs
+The maximum number of may-defs we analyze when looking for a must-def
+specifying the dynamic type of an object that invokes a virtual call
+we may be able to devirtualize speculatively.
 @end table
 @end table
 

diff --git a/gcc/ipa-polymorphic-call.c b/gcc/ipa-polymorphic-call.c
index 842ca13cd06d2a360317e2e9bdd307eef969866f..0ebbd4ae66da5ab9f02afb87e8c2f40af63d2226 100644 (file)
--- a/gcc/ipa-polymorphic-call.c
+++ b/gcc/ipa-polymorphic-call.c
@@ -38,6 +38,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-dfa.h"
 #include "gimple-pretty-print.h"
 #include "tree-into-ssa.h"
+#include "params.h"
 
 /* Return true when TYPE contains an polymorphic type and thus is interesting
    for devirtualization machinery.  */
@@ -1094,14 +1095,15 @@ struct type_change_info
   tree known_current_type;
   HOST_WIDE_INT known_current_offset;
 
+  /* Set to nonzero if we possibly missed some dynamic type changes and we
+     should consider the set to be speculative.  */
+  unsigned speculative;
+
   /* Set to true if dynamic type change has been detected.  */
   bool type_maybe_changed;
   /* Set to true if multiple types have been encountered.  known_current_type
      must be disregarded in that case.  */
   bool multiple_types_encountered;
-  /* Set to true if we possibly missed some dynamic type changes and we should
-     consider the set to be speculative.  */
-  bool speculative;
   bool seen_unanalyzed_store;
 };
 
@@ -1338,6 +1340,19 @@ record_known_type (struct type_change_info *tci, tree type, HOST_WIDE_INT offset
   tci->type_maybe_changed = true;
 }
 
+
+/* The maximum number of may-defs we visit when looking for a must-def
+   that changes the dynamic type in check_stmt_for_type_change.  Tuned
+   after the PR12392 testcase which unlimited spends 40% time within
+   these alias walks and 8% with the following limit.  */
+
+static inline bool
+csftc_abort_walking_p (unsigned speculative)
+{
+  unsigned max = PARAM_VALUE (PARAM_MAX_SPECULATIVE_DEVIRT_MAYDEFS);
+  return speculative > max ? true : false;
+}
+
 /* Callback of walk_aliased_vdefs and a helper function for
    detect_type_change to check whether a particular statement may modify
    the virtual table pointer, and if possible also determine the new type of
@@ -1384,15 +1399,15 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data)
                                          &size, &max_size, &reverse);
            if (size != max_size || max_size == -1)
              {
-                tci->speculative = true;
-               return false;
+                tci->speculative++;
+               return csftc_abort_walking_p (tci->speculative);
              }
            if (op && TREE_CODE (op) == MEM_REF)
              {
                if (!tree_fits_shwi_p (TREE_OPERAND (op, 1)))
                  {
-                    tci->speculative = true;
-                   return false;
+                    tci->speculative++;
+                   return csftc_abort_walking_p (tci->speculative);
                  }
                offset += tree_to_shwi (TREE_OPERAND (op, 1))
                          * BITS_PER_UNIT;
@@ -1402,8 +1417,8 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data)
              ;
            else
              {
-                tci->speculative = true;
-               return false;
+                tci->speculative++;
+               return csftc_abort_walking_p (tci->speculative);
              }
            op = walk_ssa_copies (op);
          }
@@ -1438,8 +1453,8 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data)
           fprintf (dump_file, "  Function call may change dynamic type:");
          print_gimple_stmt (dump_file, stmt, 0, 0);
        }
-     tci->speculative = true;
-     return false;
+     tci->speculative++;
+     return csftc_abort_walking_p (tci->speculative);
    }
   /* Check for inlined virtual table store.  */
   else if (noncall_stmt_may_be_vtbl_ptr_store (stmt))
@@ -1461,7 +1476,7 @@ check_stmt_for_type_change (ao_ref *ao ATTRIBUTE_UNUSED, tree vdef, void *data)
          if (dump_file)
            fprintf (dump_file, "  Unanalyzed store may change type.\n");
          tci->seen_unanalyzed_store = true;
-         tci->speculative = true;
+         tci->speculative++;
        }
       else
         record_known_type (tci, type, offset);
@@ -1646,7 +1661,7 @@ ipa_polymorphic_call_context::get_dynamic_type (tree instance,
   tci.otr_type = otr_type;
   tci.type_maybe_changed = false;
   tci.multiple_types_encountered = false;
-  tci.speculative = false;
+  tci.speculative = 0;
   tci.seen_unanalyzed_store = false;
 
   walk_aliased_vdefs (&ao, gimple_vuse (stmt), check_stmt_for_type_change,

diff --git a/gcc/params.def b/gcc/params.def
index 9362c1588de87ec6d7c963f6ebe5c26fc4f671da..dbff305b7f40a2ff36170785a1097757e6a76dd0 100644 (file)
--- a/gcc/params.def
+++ b/gcc/params.def
@@ -1203,6 +1203,12 @@ DEFPARAM (PARAM_HSA_GEN_DEBUG_STORES,
          "hsa-gen-debug-stores",
          "Level of hsa debug stores verbosity",
          0, 0, 1)
+
+DEFPARAM (PARAM_MAX_SPECULATIVE_DEVIRT_MAYDEFS,
+         "max-speculative-devirt-maydefs",
+         "Maximum number of may-defs visited when devirtualizing "
+         "speculatively", 50, 0, 0)
+
 /*
 
 Local variables: