Improve --trace-gvn debug output

src/hydrogen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1534 matching lines @@
     if (block->HasParentLoopHeader()) {
       int header_id = block->parent_loop_header()->block_id();
       loop_side_effects_[header_id].Add(block->IsLoopHeader()
                                         ? loop_side_effects_[id]
                                         : side_effects);
     }
   }
 }
 
 
+#if DEBUG
+SmartArrayPointer<char> GetGVNFlagsString(GVNFlagSet flags) {
+  char buffer[kLastFlag * 128];
+  const char* separator = "";
+  const char* comma = ", ";
+  buffer[0] = 0;
+  uint32_t set_depends_on = 0;
+  uint32_t set_changes = 0;
+  for (int bit = 0; bit < 31; ++bit) {

[Michael Starzinger, 2012/04/24 15:04:08]

Better use "kAfterLastFlag" instead of "31" here.

+    if ((flags.ToIntegral() & (1 << bit)) != 0) {
+      if (bit % 2 == 0) {
+        set_changes++;
+      } else {
+        set_depends_on++;
+      }
+    }
+  }
+  bool positive_changes = set_changes < 8;

[Michael Starzinger, 2012/04/24 15:04:08]

It would also be nice if "8" would somehow be based on the number of GVN flags.
Currently "set_changes <= kAfterLastFlag / 4" would probably do the trick. But I
don't know if that is less hacky.

+  bool positive_depends_on = set_depends_on < 8;
+  if (set_changes > 0) {
+    if (positive_changes) {
+      strcat(buffer, "changes [");
+    } else {
+      strcat(buffer, "changes all except [");
+    }
+    for (int bit = 0; bit < 31; ++bit) {

[Michael Starzinger, 2012/04/24 15:04:08]

Likewise.

+      if (((flags.ToIntegral() & (1 << bit)) != 0) == positive_changes) {
+        switch (static_cast<GVNFlag>(bit)) {
+#define DECLARE_FLAG(type)                \
+          case kChanges##type:            \
+            strcat(buffer, separator);    \
+            strcat(buffer, #type);        \
+            separator = comma;            \
+            break;
+GVN_TRACKED_FLAG_LIST(DECLARE_FLAG)
+GVN_UNTRACKED_FLAG_LIST(DECLARE_FLAG)
+#undef DECLARE_FLAG
+          default:
+              break;
+        }
+      }
+    }
+    strcat(buffer, "]");
+  }
+  if (set_depends_on > 0) {
+    separator = "";
+    if (set_changes > 0) {
+      strcat(buffer, ", ");
+    }
+    if (positive_depends_on) {
+      strcat(buffer, "depends on [");
+    } else {
+      strcat(buffer, "depends on all except [");
+    }
+    for (int bit = 0; bit < 31; ++bit) {

[Michael Starzinger, 2012/04/24 15:04:08]

Likewise.

+      if (((flags.ToIntegral() & (1 << bit)) != 0) == positive_depends_on) {
+        switch (static_cast<GVNFlag>(bit)) {
+#define DECLARE_FLAG(type)                  \
+          case kDependsOn##type:            \
+            strcat(buffer, separator);      \
+            strcat(buffer, #type);          \
+            separator = comma;              \
+            break;
+GVN_TRACKED_FLAG_LIST(DECLARE_FLAG)
+GVN_UNTRACKED_FLAG_LIST(DECLARE_FLAG)
+#undef DECLARE_FLAG
+          default:
+            break;
+        }
+      }
+    }
+    strcat(buffer, "]");
+  }
+  char* result = new char[strlen(buffer) + 1];
+  strcpy(result, buffer);
+  return SmartArrayPointer<char>(result);
+}
+#endif
+
+
 void HGlobalValueNumberer::LoopInvariantCodeMotion() {
   for (int i = graph_->blocks()->length() - 1; i >= 0; --i) {
     HBasicBlock* block = graph_->blocks()->at(i);
     if (block->IsLoopHeader()) {
       GVNFlagSet side_effects = loop_side_effects_[block->block_id()];
-      TraceGVN("Try loop invariant motion for block B%d effects=0x%x\n",
+      TraceGVN("Try loop invariant motion for block B%d %s\n",
                block->block_id(),
-               side_effects.ToIntegral());
+               *GetGVNFlagsString(side_effects));
 
       GVNFlagSet accumulated_first_time_depends;
       GVNFlagSet accumulated_first_time_changes;
       HBasicBlock* last = block->loop_information()->GetLastBackEdge();
       for (int j = block->block_id(); j <= last->block_id(); ++j) {
         ProcessLoopBlock(graph_->blocks()->at(j), block, side_effects,
                          &accumulated_first_time_depends,
                          &accumulated_first_time_changes);
       }
     }
   }
 }
 
 
 void HGlobalValueNumberer::ProcessLoopBlock(
     HBasicBlock* block,
     HBasicBlock* loop_header,
     GVNFlagSet loop_kills,
     GVNFlagSet* first_time_depends,
     GVNFlagSet* first_time_changes) {
   HBasicBlock* pre_header = loop_header->predecessors()->at(0);
   GVNFlagSet depends_flags = HValue::ConvertChangesToDependsFlags(loop_kills);
-  TraceGVN("Loop invariant motion for B%d depends_flags=0x%x\n",
+  TraceGVN("Loop invariant motion for B%d %s\n",
            block->block_id(),
-           depends_flags.ToIntegral());
+           *GetGVNFlagsString(depends_flags));
   HInstruction* instr = block->first();
   while (instr != NULL) {
     HInstruction* next = instr->next();
     bool hoisted = false;
     if (instr->CheckFlag(HValue::kUseGVN)) {
-      TraceGVN("Checking instruction %d (%s) instruction GVN flags 0x%X, "
-               "loop kills 0x%X\n",
+      TraceGVN("Checking instruction %d (%s) %s. Loop %s\n",
                instr->id(),
                instr->Mnemonic(),
-               instr->gvn_flags().ToIntegral(),
-               depends_flags.ToIntegral());
+               *GetGVNFlagsString(instr->gvn_flags()),
+               *GetGVNFlagsString(loop_kills));
       bool can_hoist = !instr->gvn_flags().ContainsAnyOf(depends_flags);
       if (instr->IsTransitionElementsKind()) {
         // It's possible to hoist transitions out of a loop as long as the
         // hoisting wouldn't move the transition past a DependsOn of one of it's
         // changes or any instructions that might change an objects map or
         // elements contents.
         GVNFlagSet changes = instr->ChangesFlags();
         GVNFlagSet hoist_depends_blockers =
             HValue::ConvertChangesToDependsFlags(changes);
         // In addition to not hoisting transitions above other instructions that
         // change dependencies that the transition changes, it must not be
         // hoisted above map changes and stores to an elements backing store
         // that the transition might change.
         GVNFlagSet hoist_change_blockers = changes;
         hoist_change_blockers.Add(kChangesMaps);
         HTransitionElementsKind* trans = HTransitionElementsKind::cast(instr);
         if (trans->original_map()->has_fast_double_elements()) {
           hoist_change_blockers.Add(kChangesDoubleArrayElements);
         }
         if (trans->transitioned_map()->has_fast_double_elements()) {
           hoist_change_blockers.Add(kChangesArrayElements);
         }
         TraceGVN("Checking dependencies on HTransitionElementsKind %d (%s) "
-                 "hoist depends blockers 0x%X, hoist change blockers 0x%X, "
-                 "accumulated depends 0x%X, accumulated changes 0x%X\n",
+                 "hoist blockers: %s %s; "
+                 "first-time accumulated: %s %s\n",
                  instr->id(),
                  instr->Mnemonic(),
-                 hoist_depends_blockers.ToIntegral(),
-                 hoist_change_blockers.ToIntegral(),
-                 first_time_depends->ToIntegral(),
-                 first_time_changes->ToIntegral());
+                 *GetGVNFlagsString(hoist_depends_blockers),
+                 *GetGVNFlagsString(hoist_change_blockers),
+                 *GetGVNFlagsString(*first_time_depends),
+                 *GetGVNFlagsString(*first_time_changes));
         // It's possible to hoist transition from the current loop loop only if
         // they dominate all of the successor blocks in the same loop and there
         // are not any instructions that have Changes/DependsOn that intervene
         // between it and the beginning of the loop header.
         bool in_nested_loop = block != loop_header &&
             ((block->parent_loop_header() != loop_header) ||
              block->IsLoopHeader());
         can_hoist = !in_nested_loop &&
             block->IsLoopSuccessorDominator() &&
             !first_time_depends->ContainsAnyOf(hoist_depends_blockers) &&
@@ skipping 14 matching lines @@
           instr->Unlink();
           instr->InsertBefore(pre_header->end());
           if (instr->HasSideEffects()) removed_side_effects_ = true;
           hoisted = true;
         }
       }
     }
     if (!hoisted) {
       // If an instruction is not hoisted, we have to account for its side
       // effects when hoisting later HTransitionElementsKind instructions.
+      GVNFlagSet previous_depends = *first_time_depends;
+      GVNFlagSet previous_changes = *first_time_changes;
       first_time_depends->Add(instr->DependsOnFlags());
       first_time_changes->Add(instr->ChangesFlags());
+      if (!(previous_depends == *first_time_depends)) {
+        TraceGVN("Updated first-time accumulated %s\n",
+                 *GetGVNFlagsString(*first_time_depends));
+      }
+      if (!(previous_changes == *first_time_changes)) {
+        TraceGVN("Updated first-time accumulated %s\n",
+                 *GetGVNFlagsString(*first_time_changes));
+      }
     }
     instr = next;
   }
 }
 
 
 bool HGlobalValueNumberer::AllowCodeMotion() {
   return info()->shared_info()->opt_count() + 1 < Compiler::kDefaultMaxOptCount;
 }
 
@@ skipping 6690 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal