[turbofan] Get rid of SourcePositionInstruction.

src/compiler/jump-threading.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/jump-threading.h"
 #include "src/compiler/code-generator-impl.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
@@ skipping 62 matching lines @@
       TRACE("jt [%d] B%d\n", static_cast<int>(stack.size()),
             block->rpo_number().ToInt());
       bool fallthru = true;
       RpoNumber fw = block->rpo_number();
       for (int i = block->code_start(); i < block->code_end(); ++i) {
         Instruction* instr = code->InstructionAt(i);
         if (!instr->AreMovesRedundant()) {
           // can't skip instructions with non redundant moves.
           TRACE("  parallel move\n");
           fallthru = false;
-        } else if (instr->IsSourcePosition()) {
-          // skip source positions.
-          TRACE("  src pos\n");
-          continue;
         } else if (FlagsModeField::decode(instr->opcode()) != kFlags_none) {
           // can't skip instructions with flags continuations.
           TRACE("  flags\n");
           fallthru = false;
         } else if (instr->IsNop()) {
           // skip nops.
           TRACE("  nop\n");
           continue;
         } else if (instr->arch_opcode() == kArchJmp) {
           // try to forward the jump instruction.
@@ skipping 90 matching lines @@
     if (block->IsDeferred()) {
       block->set_ao_number(RpoNumber::FromInt(ao));
       if (!skip[block->rpo_number().ToInt()]) ao++;
     }
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8