[turbofan] address nits for "[turbofan] Masking/poisoning in codegen (optimized code, x64)"

https://chromium-review.googlesource.com/c/v8/v8/+/901625 was committed without the nits addressed. This addresses the outstanding comments.

Change-Id: Ibefca64ddcfddf1d6c4138647434af331c18a801
Reviewed-on: https://chromium-review.googlesource.com/918762Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51289}

src/compiler/code-generator.cc

@@ -141,8 +141,6 @@ void CodeGenerator::AssembleCode() {
   // the frame (that is done in AssemblePrologue).
   FrameScope frame_scope(tasm(), StackFrame::MANUAL);
 
-  InitializePoisonForLoadsIfNeeded();
-
   if (info->is_source_positions_enabled()) {
     AssembleSourcePosition(start_source_position());
   }
@@ -160,6 +158,8 @@ void CodeGenerator::AssembleCode() {
 
   if (info->is_speculation_poison_enabled()) {
     GenerateSpeculationPoison();
+  } else {
+    InitializePoisonForLoadsIfNeeded();
   }
 
   // TODO(jupvfranco): This should be the first thing in the code after

src/compiler/instruction-selector.cc

@@ -1005,6 +1005,7 @@ void InstructionSelector::VisitControl(BasicBlock* block) {
       return VisitTailCall(input);
     }
     case BasicBlock::kBranch: {
+      DCHECK_EQ(IrOpcode::kBranch, input->opcode());
       BasicBlock* tbranch = block->SuccessorAt(0);
       BasicBlock* fbranch = block->SuccessorAt(1);
       if (tbranch == fbranch) return VisitGoto(tbranch);

src/compiler/instruction-selector.h

@@ -41,6 +41,7 @@ struct PushParameter {
 };
 
 enum class FrameStateInputKind { kAny, kStackSlot };
+
 // Instruction selection generates an InstructionSequence for a given Schedule.
 class V8_EXPORT_PRIVATE InstructionSelector final {
  public:

src/compiler/jump-threading.cc

@@ -123,11 +123,12 @@ bool JumpThreading::ComputeForwarding(Zone* local_zone,
             fallthru = false;
           }
           break;
-      }
-      if (fallthru) {
-        int next = 1 + block->rpo_number().ToInt();
-        if (next < code->InstructionBlockCount()) fw = RpoNumber::FromInt(next);
-      }
+        }
+        if (fallthru) {
+          int next = 1 + block->rpo_number().ToInt();
+          if (next < code->InstructionBlockCount())
+            fw = RpoNumber::FromInt(next);
+        }
       }
       state.Forward(fw);
     }

src/compiler/pipeline.cc

@@ -2207,7 +2207,6 @@ bool PipelineImpl::SelectInstructions(Linkage* linkage) {
     AllocateRegisters(config.get(), call_descriptor, run_verifier);
   } else if (data->info()->is_poison_loads()) {
     CHECK(InstructionSelector::SupportsSpeculationPoisoning());
-    CHECK_NE(kSpeculationPoisonRegister, Register::no_reg());
     AllocateRegisters(RegisterConfiguration::Poisoning(), call_descriptor,
                       run_verifier);
   } else {

src/compiler/verifier.cc

@@ -268,7 +268,7 @@ void Verifier::Visitor::Check(Node* node, const AllNodes& all) {
     case IrOpcode::kIfTrue:
     case IrOpcode::kIfFalse: {
       Node* control = NodeProperties::GetControlInput(node, 0);
-      CHECK(control->opcode() == IrOpcode::kBranch);
+      CHECK_EQ(IrOpcode::kBranch, control->opcode());
       // Type is empty.
       CheckNotTyped(node);
       break;