[interpreter] Faster and fewer flushes in register optimizer.

test/cctest/interpreter/bytecode_expectations/WideRegisters.golden

 #
 # Autogenerated by generate-bytecode-expectations.
 #
 
 ---
 pool type: number
 execute: yes
 wrap: yes
 
 ---
@@ skipping 689 matching lines @@
   var x154;
   var x155;
   var x156;
   var x0 = 0;
   if (x129 == 3) { var x129 = x0; }
   if (x2 > 3) { return x0; }
   return x129;
 "
 frame size: 157
 parameter count: 1
-bytecode array length: 39
+bytecode array length: 37
 bytecodes: [
   /*   30 E> */ B(StackCheck),
   /* 1503 S> */ B(LdaZero),
                 B(Star), R(0),
   /* 1506 S> */ B(LdaSmi), U8(3),
   /* 1515 E> */ B(Wide), B(TestEqual), R16(129),
-                B(JumpIfFalse), U8(13),
+                B(JumpIfFalse), U8(11),
   /* 1534 S> */ B(Nop),
   /* 1534 E> */ B(Wide), B(Mov), R16(0), R16(129),
-                B(Wide), B(Ldar), R16(129),
+                B(Ldar), R(0),
   /* 1540 S> */ B(LdaSmi), U8(3),
   /* 1547 E> */ B(Wide), B(TestGreaterThan), R16(2),
                 B(JumpIfFalse), U8(5),
   /* 1554 S> */ B(Ldar), R(0),
   /* 1580 S> */ B(Return),
   /* 1567 S> */ B(Wide), B(Ldar), R16(129),
   /* 1580 S> */ B(Return),
 ]
 constant pool: [
 ]
@@ skipping 580 matching lines @@
                 B(Star), R(1),
   /* 1537 S> */ B(CallRuntime), U16(Runtime::kTheHole), R(0), U8(0),
   /* 1549 S> */ B(Ldar), R(1),
   /* 1560 S> */ B(Return),
 ]
 constant pool: [
 ]
 handlers: [
 ]