Recognize and optimize a.runtimeType == b.runtimeType pattern.

runtime/vm/assembler_arm64.cc

Index: runtime/vm/assembler_arm64.cc
diff --git a/runtime/vm/assembler_arm64.cc b/runtime/vm/assembler_arm64.cc
index 72278e967a219aeda1961063fdf09d5000085159..dde11c270453b2743cd3aa3507cbf1be94570781 100644
--- a/runtime/vm/assembler_arm64.cc
+++ b/runtime/vm/assembler_arm64.cc
@@ -682,6 +682,24 @@ void Assembler::SubImmediateSetFlags(Register dest, Register rn, int64_t imm) {
 }
 
 
+void Assembler::SubImmediate(Register dest, Register rn, int64_t imm) {

[regis, 2016/10/08 09:10:37]

Same comment as for arm.

[Vyacheslav Egorov (Google), 2016/10/24 20:23:03]

Done.

+  Operand op;
+  if (Operand::CanHold(imm, kXRegSizeInBits, &op) == Operand::Immediate) {
+    // Handles imm == kMinInt64.
+    sub(dest, rn, op);
+  } else if (Operand::CanHold(-imm, kXRegSizeInBits, &op) ==
+             Operand::Immediate) {
+    ASSERT(imm != kMinInt64);  // Would cause erroneous overflow detection.
+    add(dest, rn, op);
+  } else {
+    // TODO(zra): Try subtracting top 12 bits, then bottom 12 bits.
+    ASSERT(rn != TMP2);
+    LoadImmediate(TMP2, imm);
+    sub(dest, rn, Operand(TMP2));
+  }
+}
+
+
 void Assembler::AndImmediate(Register rd, Register rn, int64_t imm) {
   Operand imm_op;
   if (Operand::IsImmLogical(imm, kXRegSizeInBits, &imm_op)) {