Instruction selection before removing HTypeKnown

Instruction selection before removing HTypeKnown


Example for HIdentity - this is quite rare because we don't strengthen types on 'if (x == null)'

      ...
      t1.appendChild(element);
      t2 = J.get$form$x(element);
      return t2 == null ? t1 == null : t2 === t1;
--->
      ...
      t1.appendChild(element);  // t1 can't be null after here
      return J.get$form$x(element) === t1;

Example of HIsViaInterceptor (0.50% smaller swarm)

      t1 = J.getInterceptor(x);
      if (typeof x === "object" && x !== null && (x.constructor === Array || !!t1.$isList))
        return this.visitList$1(x);
      if (typeof x === "object" && x !== null && !!t1.$isMap)
        return this.visitMap$1(x);
      if (typeof x === "object" && x !== null && !!t1.$isSendPort)
        return this.visitSendPort$1(x);
--->
      t1 = J.getInterceptor(x);
      if (!!t1.$isList)
        return this.visitList$1(x);
      if (!!t1.$isMap)
        return this.visitMap$1(x);
      if (!!t1.$isSendPort)
        return this.visitSendPort$1(x);

R=floitsch@google.com

Committed: https://code.google.com/p/dart/source/detail?r=33510

[sra1, 2014-03-08 02:57:21]

What do you think of this 'instruction selection' phase to introduce new
instructions that make codegen better or easier?

---

Another one in this category would be a read-modify-write instruction that
combines certain load/op/store instructions.
Example:

        t1 = init.globalState;
        t2 = t1.nextIsolateId;
        t1.nextIsolateId = t2 + 1;
        ...t2...
-->
        t1 = init.globalState
        t2 = ++t1.nextIsolateId;
        ...t2...

And
        buffer._contents = buffer._contents + ", ";
-->
        buffer._contents += ", ";

I don't think it will be a huge size win but the generated code would look more
competent.

[floitsch, 2014-03-10 17:35:31]

LGTM with tests.

[sra1, 2014-03-11 00:06:28]

Committed patchset #2 manually as r33510 (presubmit successful).