RFR: 8262341: Refine identical code in AddI/LNode.

[Eric Liu]

On Tue, 30 Nov 2021 08:39:52 GMT, Roland Westrelin <roland at openjdk.org> wrote:

> AddINode::Ideal() and AddlNode::Ideal() are almost identical but the
> same logic had to be duplicated because AddINode::Ideal() tests its
> inputs for Op_AddI, Op_SubI etc. while AddLNode::Ideal() tests for
> Op_AddL, Op_SubL etc. This patch refactors the code so the common
> logic is in a single method parameterized by a BasicType argument.
> 
> The way I've done this before in the context of int/long counted loops
> was to use and extra virtual method operates_on(). So:
> 
> n->Opcode() == Op_AddI becomes n->is_Add() && n->operates_on(T_INT)
> 
> Working on this change made me realize that pattern doesn't work that well:
> 
> - it's quite a bit more verbose and converting existing code is not as
>   mechanical as we would like to avoid conversion errors.
> 
> - it breaks when a class has a subclass. For instance AddNode has
>   OrINode and OrLNode as subclasses so testing for n->is_Add() returns
>   true with an OrI node.
> 
> Instead, this change introduces new functions. For instance of
> AddI/AddL:
> 
> int Op_Add(BasicType bt)
> 
> that returns either Op_AddI or Op_AddL depending on bt. This made
> refactoring the AddINode::Ideal() logic straightforward. I removed all
> use of operates_on() as well and converted existing code to the new
> Op_XXX() functions.

src/hotspot/share/opto/addnode.cpp line 280:

> 278:   }
> 279:   if (op1 == Op_Sub(bt)) {
> 280:     const Type *t_sub1 = phase->type(in1->in(1));

I'm not very clear about the current code style which we should follow. Shall we need to align the style in the changed code?

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PR: https://git.openjdk.java.net/jdk/pull/6607