[turbofan] Treat uninitialized source positions as unknown.

src/compiler/instruction-selector.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/instruction-selector.h"
 
 #include <limits>
 
 #include "src/base/adapters.h"
 #include "src/compiler/instruction-selector-impl.h"
@@ skipping 405 matching lines @@
     // Skip nodes that are unused or already defined.
     if (!IsUsed(node) || IsDefined(node)) continue;
     // Generate code for this node "top down", but schedule the code "bottom
     // up".
     size_t current_node_end = instructions_.size();
     VisitNode(node);
     std::reverse(instructions_.begin() + current_node_end, instructions_.end());
     if (instructions_.size() == current_node_end) continue;
     // Mark source position on first instruction emitted.
     SourcePosition source_position = source_positions_->GetSourcePosition(node);
-    if (source_position.IsUnknown()) continue;
-    DCHECK(!source_position.IsInvalid());
-    if (source_position_mode_ == kAllSourcePositions ||
-        node->opcode() == IrOpcode::kCall) {
+    if (source_position.IsKnown() &&
+        (source_position_mode_ == kAllSourcePositions ||
+         node->opcode() == IrOpcode::kCall)) {
       sequence()->SetSourcePosition(instructions_[current_node_end],
                                     source_position);
     }
   }
 
   // We're done with the block.
   InstructionBlock* instruction_block =
       sequence()->InstructionBlockAt(RpoNumber::FromInt(block->rpo_number()));
   instruction_block->set_code_start(static_cast<int>(instructions_.size()));
   instruction_block->set_code_end(current_block_end);
@@ skipping 704 matching lines @@
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
   return MachineOperatorBuilder::Flag::kNoFlags;
 }
 
 #endif  // !V8_TURBOFAN_BACKEND
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8