[turbofan] Optimize certain chains of Branch into a Switch.

src/compiler/common-operator.cc

Index: src/compiler/common-operator.cc
diff --git a/src/compiler/common-operator.cc b/src/compiler/common-operator.cc
index eda99d4fee0d2a94adc4bbc47514705ef99d64f3..8aea3df5adc85867877924a94d78aeae6928c174 100644
--- a/src/compiler/common-operator.cc
+++ b/src/compiler/common-operator.cc
@@ -36,12 +36,6 @@ BranchHint BranchHintOf(const Operator* const op) {
 }
 
 
-size_t CaseIndexOf(const Operator* const op) {
-  DCHECK_EQ(IrOpcode::kCase, op->opcode());
-  return OpParameter<size_t>(op);
-}
-
-
 bool operator==(SelectParameters const& lhs, SelectParameters const& rhs) {
   return lhs.type() == rhs.type() && lhs.hint() == rhs.hint();
 }
@@ -121,6 +115,7 @@ size_t ProjectionIndexOf(const Operator* const op) {
   V(End, Operator::kKontrol, 0, 0, 1, 0, 0, 0)             \
   V(IfTrue, Operator::kKontrol, 0, 0, 1, 0, 0, 1)          \
   V(IfFalse, Operator::kKontrol, 0, 0, 1, 0, 0, 1)         \
+  V(IfDefault, Operator::kKontrol, 0, 0, 1, 0, 0, 1)       \
   V(Throw, Operator::kFoldable, 1, 1, 1, 0, 0, 1)          \
   V(Return, Operator::kNoThrow, 1, 1, 1, 0, 0, 1)          \
   V(OsrNormalEntry, Operator::kFoldable, 0, 1, 1, 0, 1, 1) \
@@ -256,7 +251,7 @@ const Operator* CommonOperatorBuilder::Branch(BranchHint hint) {
 
 
 const Operator* CommonOperatorBuilder::Switch(size_t control_output_count) {
-  DCHECK_GE(control_output_count, 2u);        // Disallow trivial switches.
+  DCHECK_GE(control_output_count, 3u);        // Disallow trivial switches.
   return new (zone()) Operator(               // --
       IrOpcode::kSwitch, Operator::kKontrol,  // opcode
       "Switch",                               // name
@@ -264,12 +259,12 @@ const Operator* CommonOperatorBuilder::Switch(size_t control_output_count) {
 }
 
 
-const Operator* CommonOperatorBuilder::Case(size_t index) {
-  return new (zone()) Operator1<size_t>(    // --
-      IrOpcode::kCase, Operator::kKontrol,  // opcode
-      "Case",                               // name
-      0, 0, 1, 0, 0, 1,                     // counts
-      index);                               // parameter
+const Operator* CommonOperatorBuilder::IfValue(int32_t index) {
+  return new (zone()) Operator1<int32_t>(      // --
+      IrOpcode::kIfValue, Operator::kKontrol,  // opcode
+      "IfValue",                               // name
+      0, 0, 1, 0, 0, 1,                        // counts
+      index);                                  // parameter
 }