RFR: 8277882: New subnode ideal optimization: converting "c0 - (x + c1)" into "(c0 - c1) - x" [v4]

[Mai Đặng Quân Anh]

On Tue, 30 Nov 2021 22:44:59 GMT, Zang, Zhiqiang <duke at openjdk.java.net> wrote:

>> Suggest two new optimizations that can be done in SubINode::Ideal.
>
> Zang, Zhiqiang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add ok_to_convert to the condition.

src/hotspot/share/opto/subnode.cpp line 195:

> 193:   if (in2->Opcode() == Op_AddI
> 194:       && phase->type(in1)->isa_int() != NULL
> 195:       && phase->type(in1)->isa_int()->is_con()

Line 194 and 195 can be expressed as `in1->Opcode() == Op_ConI`, same for the next 2 lines.

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PR: https://git.openjdk.java.net/jdk/pull/6441