RFR: JDK-8244036 Refresh SetupJavaCompilation, and remove support for sjavac

[Magnus Ihse Bursie]

On 2020-04-29 00:35, Erik Joelsson wrote:
> Hello Magnus,
>
> Nice job! Looks good.
>
> Is the disabling of the warning "options" actually needed in that many 
> places or did you just add it everywhere where GENERATE_OLDBYTECODE 
> was used?
It is really needed -- I started out without it, and added it wherever 
the warning crept up.

My next step is to go over each java compilation and scrutinize them. 
Hopefully I can tune the options to get rid of this warning. That might 
mean that the output class files can change though, so I need to make 
sure that it's okay.
>
> Minor notes:
>
> JavaCompilation.gmk
> 39: spelling
> 206: do -> does
Thanks for catching that! I fixed it before I pushed.

/Magnus

>
> /Erik
>
> On 2020-04-28 13:37, Magnus Ihse Bursie wrote:
>> The code for setting up Java compilation has long been quite hard to 
>> understand, and has a tricky API. Part of this is due to the support 
>> for the sjavac ("smart javac") system. We do not use sjavac anymore, 
>> and it has not been tested for long. Part of the sjavac effort was 
>> extracted into the "depend" javac plugin, and another part ended up 
>> as the java server, both of which we still use.
>>
>> This patch removes the "traditional" sjavac support, keeping just the 
>> depend plugin and javac server.
>>
>> It also redesigns the SetupJavaCompilation API on how to define which 
>> compiler to use (from the boot jdk or the interim compiler built as 
>> part of the buildtools), and what JDK to target. This captures more 
>> precisely what was expressed by the cryptic "Setups" in 
>> SetupJavaCompilers.gmk.
>>
>> The generated Java code that goes into the product should be 
>> byte-by-byte identical with this patch. However, I've not applied the 
>> same level of strictness for our build tools, where I have accepted 
>> changes in bytecode to make the new API calls simpler. This does not 
>> affect the output from the build tools.
>>
>> I imagine a second pass will be needed after this, to clear up some 
>> remaining stuff. For instance, it is not clear that all instances of 
>> SetupJavaCompilation really ask for the correct thing.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8244036
>> WebRev: 
>> http://cr.openjdk.java.net/~ihse/JDK-8244036-remove-sjavac/webrev.01
>>
>> /Magnus