Revert "[turbofan] Optimize TrapIf/Unless in BranchElim. and CommonOp-Reducer"

This reverts commit a3b1233e.

Reason for revert: This approach has multiple issues and we have to reconsider it.

Original change's description:
> [turbofan] Optimize TrapIf/Unless in BranchElim. and CommonOp-Reducer
>
> Bug: v8:11510
> Change-Id: I1e8fcb54444e494c7d765ad556d09d954441361f
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2752876
> Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
> Reviewed-by: Georg Neis <neis@chromium.org>
> Reviewed-by: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#73468}

Bug: v8:11510
Change-Id: Id35bc4ebcb45a617f61993d857ad2291b0287ad6
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2772600
Auto-Submit: Manos Koukoutos <manoskouk@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#73502}

src/compiler/branch-elimination.cc

@@ -42,9 +42,6 @@ Reduction BranchElimination::Reduce(Node* node) {
       return ReduceIf(node, false);
     case IrOpcode::kIfTrue:
       return ReduceIf(node, true);
-    case IrOpcode::kTrapIf:
-    case IrOpcode::kTrapUnless:
-      return ReduceTrapConditional(node);
     case IrOpcode::kStart:
       return ReduceStart(node);
     default:
@@ -74,9 +71,9 @@ void BranchElimination::SimplifyBranchCondition(Node* branch) {
   //    |  \           /                      \           /
   //    |   \         /                        \         /
   //    |  first_merge           ==>          first_merge
-  //    |       |                              /    |
-  //   second_branch                    1  0  /     |
-  //    /          \                     \ | /      |
+  //    |       |                                   |
+  //   second_branch                    1    0      |
+  //    /          \                     \  /       |
   //   /            \                     phi       |
   // second_true  second_false              \       |
   //                                      second_branch
@@ -157,45 +154,6 @@ Reduction BranchElimination::ReduceBranch(Node* node) {
   return TakeConditionsFromFirstControl(node);
 }
 
-Reduction BranchElimination::ReduceTrapConditional(Node* node) {
-  DCHECK(node->opcode() == IrOpcode::kTrapIf ||
-         node->opcode() == IrOpcode::kTrapUnless);
-  bool trapping_condition = node->opcode() == IrOpcode::kTrapIf;
-  Node* condition = node->InputAt(0);
-  Node* control_input = NodeProperties::GetControlInput(node, 0);
-  // If we do not know anything about the predecessor, do not propagate just
-  // yet because we will have to recompute anyway once we compute the
-  // predecessor.
-  if (!reduced_.Get(control_input)) {
-    return NoChange();
-  }
-  ControlPathConditions from_input = node_conditions_.Get(control_input);
-
-  Node* branch;
-  bool condition_value;
-
-  if (from_input.LookupCondition(condition, &branch, &condition_value)) {
-    if (condition_value == trapping_condition) {
-      // This will trap, all that follows is dead.
-      for (Node* const use : node->uses()) {
-        Replace(use, dead());
-      }
-      Node* effect_input = NodeProperties::GetEffectInput(node);
-      graph()->end()->AppendInput(
-          graph()->zone(),
-          graph()->NewNode(common()->Return(0),
-                           graph()->NewNode(common()->Int32Constant(0)),
-                           effect_input, node));
-      return NoChange();
-    } else {
-      // This will not trap, remove it.
-      return Replace(control_input);
-    }
-  }
-  return UpdateConditions(node, from_input, condition, node,
-                          !trapping_condition);
-}
-
 Reduction BranchElimination::ReduceDeoptimizeConditional(Node* node) {
   DCHECK(node->opcode() == IrOpcode::kDeoptimizeIf ||
          node->opcode() == IrOpcode::kDeoptimizeUnless);
@@ -344,9 +302,7 @@ bool BranchElimination::ControlPathConditions::LookupCondition(
 
 void BranchElimination::MarkAsSafetyCheckIfNeeded(Node* branch, Node* node) {
   // Check if {branch} is dead because we might have a stale side-table entry.
-  if (!branch->IsDead() && branch->opcode() != IrOpcode::kDead &&
-      branch->opcode() != IrOpcode::kTrapIf &&
-      branch->opcode() != IrOpcode::kTrapUnless) {
+  if (!branch->IsDead() && branch->opcode() != IrOpcode::kDead) {
     IsSafetyCheck branch_safety = IsSafetyCheckOf(branch->op());
     IsSafetyCheck combined_safety =
         CombineSafetyChecks(branch_safety, IsSafetyCheckOf(node->op()));

src/compiler/branch-elimination.h

@@ -63,7 +63,6 @@ class V8_EXPORT_PRIVATE BranchElimination final
   Reduction ReduceBranch(Node* node);
   Reduction ReduceDeoptimizeConditional(Node* node);
   Reduction ReduceIf(Node* node, bool is_true_branch);
-  Reduction ReduceTrapConditional(Node* node);
   Reduction ReduceLoop(Node* node);
   Reduction ReduceMerge(Node* node);
   Reduction ReduceStart(Node* node);

src/compiler/common-operator-reducer.cc

@@ -74,9 +74,6 @@ Reduction CommonOperatorReducer::Reduce(Node* node) {
       return ReduceSwitch(node);
     case IrOpcode::kStaticAssert:
       return ReduceStaticAssert(node);
-    case IrOpcode::kTrapIf:
-    case IrOpcode::kTrapUnless:
-      return ReduceTrapConditional(node);
     default:
       break;
   }
@@ -475,33 +472,6 @@ Reduction CommonOperatorReducer::ReduceStaticAssert(Node* node) {
   }
 }
 
-Reduction CommonOperatorReducer::ReduceTrapConditional(Node* trap) {
-  DCHECK(trap->opcode() == IrOpcode::kTrapIf ||
-         trap->opcode() == IrOpcode::kTrapUnless);
-  bool trapping_condition = trap->opcode() == IrOpcode::kTrapIf;
-  Node* const cond = trap->InputAt(0);
-  Decision decision = DecideCondition(broker(), cond);
-
-  if (decision == Decision::kUnknown) {
-    return NoChange();
-  } else if ((decision == Decision::kTrue) == trapping_condition) {
-    // This will trap, all that follows is dead.
-    for (Node* const use : trap->uses()) {
-      Replace(use, dead());
-    }
-    Node* effect_input = NodeProperties::GetEffectInput(trap);
-    graph()->end()->AppendInput(
-        graph()->zone(),
-        graph()->NewNode(common()->Return(0),
-                         graph()->NewNode(common()->Int32Constant(0)),
-                         effect_input, trap));
-    return NoChange();
-  } else {
-    // This will not trap, remove it.
-    return Replace(NodeProperties::GetControlInput(trap));
-  }
-}
-
 Reduction CommonOperatorReducer::Change(Node* node, Operator const* op,
                                         Node* a) {
   node->ReplaceInput(0, a);

src/compiler/common-operator-reducer.h

@@ -43,7 +43,6 @@ class V8_EXPORT_PRIVATE CommonOperatorReducer final
   Reduction ReduceSelect(Node* node);
   Reduction ReduceSwitch(Node* node);
   Reduction ReduceStaticAssert(Node* node);
-  Reduction ReduceTrapConditional(Node* node);
 
   Reduction Change(Node* node, Operator const* op, Node* a);
   Reduction Change(Node* node, Operator const* op, Node* a, Node* b);