RFR: 8255553: [PPC64] Introduce and use setbc and setnbc P10 instructions [v7]

[Ziviani]

On Mon, 16 Nov 2020 20:33:12 GMT, Corey Ashford <github.com+51754783+CoreyAshford at openjdk.org> wrote:

>> Ziviani has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
>> 
>>   8255553: [PPC64] Introduce and use setbc and setnbc P10 instructions
>>   
>>   - setbc RT,BI: sets RT to 1 if CR(BI) is 1, otherwise 0.
>>   - setnbc RT,BI: sets RT to -1 if CR(BI) is 1, otherwise 0.
>>   Ref: PowerISA 3.1, page 129.
>>   
>>   These instructions are particularly interesting to improve the following
>>   pattern `(src1<src2)? -1: ((src1>src2)? 1: 0)`, which can be found in
>>   `instruct cmpL3_reg_reg_ExEx()@ppc.ad`, by removing its branches.
>>   
>>   Long.toString, that generate such pattern in getChars, has showed a
>>   good performance gain by using these new instructions.
>>   
>>   Example:
>>   for (int i = 0; i < 200_000; i++)
>>     res = Long.toString((long)i);
>>   
>>   java -Xcomp -XX:CompileThreshold=1 -XX:-TieredCompilation TestToString
>>   
>>   Without setbc (average): 0.1178 seconds
>>   With setbc (average): 0.0396 seconds
>
> src/hotspot/cpu/ppc/macroAssembler_ppc.inline.hpp line 239:
> 
>> 237: }
>> 238: 
>> 239: // set dst to -1, 0, +1
> 
> Comment should be something like:
> set dst to -1, 0, +1, as follows: (some description)

Added this comment:
// set dst to -1, 0, +1 as follows: if CCR0bi is "greater than", dst is set to 1,
// if CCR0bi is "equal", dst is set to 0, otherwise it's set to -1.

> src/hotspot/cpu/ppc/macroAssembler_ppc.hpp line 164:
> 
>> 162:   // branch, jump
>> 163:   //
>> 164:   // set dst to -1, 0, +1
> 
> Comment should be something like:
> set dst to -1, 0, +1, as follows: (some description)

Added this comment:
// set dst to -1, 0, +1 as follows: if CCR0bi is "greater than", dst is set to 1,
// if CCR0bi is "equal", dst is set to 0, otherwise it's set to -1.

> src/hotspot/cpu/ppc/templateTable_ppc_64.cpp line 1613:
> 
>> 1611:   // if unordered_result is 1, treat unordered_result like 'greater than'
>> 1612:   assert(unordered_result == 1 || unordered_result == -1, "only supported");
>> 1613:   __ set_cmpu3(R17_tos, (unordered_result == 1) ? false : true);
> 
> instead of `(unordered_result == 1) ? false : true`
> 
> how about `unordered_result != 1`

done, thanks !

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PR: https://git.openjdk.java.net/jdk/pull/907