Simplify known successor block lowering.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 3989db2580ede5ab19f3fd9496ad022439c337a1..5465056bc7fc2e36c5bb7677cdc9fd25a2b02aba 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -849,7 +849,14 @@ void LChunkBuilder::VisitInstruction(HInstruction* current) {
       chunk_->AddInstruction(dummy, current_block_);
     }
   } else {
-    instr = current->CompileToLithium(this);
+    HBasicBlock* successor;
+    if (current->IsControlInstruction() &&
+        HControlInstruction::cast(current)->KnownSuccessorBlock(&successor) &&
+        successor != NULL) {
+      instr = new(zone()) LGoto(successor);
+    } else {
+      instr = current->CompileToLithium(this);
+    }
   }
 
   argument_count_ += current->argument_delta();
@@ -940,9 +947,6 @@ LInstruction* LChunkBuilder::DoDebugBreak(HDebugBreak* instr) {
 
 
 LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
-  LInstruction* goto_instr = CheckElideControlInstruction(instr);
-  if (goto_instr != NULL) return goto_instr;
-
   HValue* value = instr->value();
   Representation r = value->representation();
   HType type = value->type();
@@ -962,9 +966,6 @@ LInstruction* LChunkBuilder::DoBranch(HBranch* instr) {
 
 
 LInstruction* LChunkBuilder::DoCompareMap(HCompareMap* instr) {
-  LInstruction* goto_instr = CheckElideControlInstruction(instr);
-  if (goto_instr != NULL) return goto_instr;
-
   ASSERT(instr->value()->representation().IsTagged());
   LOperand* value = UseRegisterAtStart(instr->value());
   return new(zone()) LCmpMapAndBranch(value);
@@ -1609,8 +1610,6 @@ LInstruction* LChunkBuilder::DoCompareGeneric(HCompareGeneric* instr) {
 
 LInstruction* LChunkBuilder::DoCompareNumericAndBranch(
     HCompareNumericAndBranch* instr) {
-  LInstruction* goto_instr = CheckElideControlInstruction(instr);
-  if (goto_instr != NULL) return goto_instr;
   Representation r = instr->representation();
   if (r.IsSmiOrInteger32()) {
     ASSERT(instr->left()->representation().Equals(r));
@@ -1638,8 +1637,6 @@ LInstruction* LChunkBuilder::DoCompareNumericAndBranch(
 
 LInstruction* LChunkBuilder::DoCompareObjectEqAndBranch(
     HCompareObjectEqAndBranch* instr) {
-  LInstruction* goto_instr = CheckElideControlInstruction(instr);
-  if (goto_instr != NULL) return goto_instr;
   LOperand* left = UseRegisterAtStart(instr->left());
   LOperand* right = UseRegisterOrConstantAtStart(instr->right());
   return new(zone()) LCmpObjectEqAndBranch(left, right);
@@ -1655,8 +1652,6 @@ LInstruction* LChunkBuilder::DoCompareHoleAndBranch(
 
 LInstruction* LChunkBuilder::DoCompareMinusZeroAndBranch(
     HCompareMinusZeroAndBranch* instr) {
-  LInstruction* goto_instr = CheckElideControlInstruction(instr);
-  if (goto_instr != NULL) return goto_instr;
   LOperand* value = UseRegister(instr->value());
   return new(zone()) LCompareMinusZeroAndBranch(value);
 }
@@ -2496,9 +2491,6 @@ LInstruction* LChunkBuilder::DoTypeof(HTypeof* instr) {
 
 
 LInstruction* LChunkBuilder::DoTypeofIsAndBranch(HTypeofIsAndBranch* instr) {
-  LInstruction* goto_instr = CheckElideControlInstruction(instr);
-  if (goto_instr != NULL) return goto_instr;
-
   return new(zone()) LTypeofIsAndBranch(UseTempRegister(instr->value()));
 }