Request for review: 6896617: Optimize sun.nio.cs.ISO_8859_1$Encode.encodeArrayLoop() on x86

[Vitaly Davidovich]

I was sure CSE was done but didn't know about SplitIf, very cool.

Thanks

Sent from my phone
On Jan 9, 2013 9:11 PM, "Vladimir Kozlov" <vladimir.kozlov at oracle.com>
wrote:

> On 1/9/13 5:11 PM, Vitaly Davidovich wrote:
>
>> One could write this as:
>> boolean overflow = false;
>> if (len > (dl - dp))
>> {
>>    overflow = true;
>>     len = dl - dp;
>> }
>>
>> One would hope jit can do this automatically and also CSE away the dl -
>> dp bit. :)
>>
>
> Yes, JIT can convert Ulf's code into above code - SplitIf optimization in
> C2. But it could be complicated by surrounding code.
> And generating only one dl-dp is regular optimization which JIT does.
>
> Thanks,
> Vladimir
>
>
>> Sent from my phone
>>
>> On Jan 9, 2013 7:39 PM, "Vladimir Kozlov" <vladimir.kozlov at oracle.com
>> <mailto:vladimir.kozlov@**oracle.com <vladimir.kozlov at oracle.com>>>
>> wrote:
>>
>>      From JIT compiler view current code is better since it has only one
>>     compare. Your code has two compares: one to calculate "overflow" and
>>     an other (depended on first) to calculate "len".
>>
>>     Thanks,
>>     Vladimir
>>
>>     On 1/9/13 3:57 PM, Ulf Zibis wrote:
>>
>>         Another little simplification:
>>             179             boolean overflow = sr > dr;
>>             180             sr = overflow ? dr : sr;
>>         or in your existing logic:
>>            178             int len = sl - sp;
>>            179             boolean overflow = len > (dl - dp);
>>            180             len = overflow ? dl - dp : len;
>>         (len is equivalent to sr)
>>
>>         -Ulf
>>
>>         Am 09.01.2013 19:03, schrieb Vladimir Kozlov:
>>
>>             Ulf,
>>
>>             Thank you for this suggestion but I would like to keep
>>             surrounding
>>             code intact. I will rename "overflowflag" to "overflow". It
>>             is used to
>>             indicate that we should return CoderResult.OVERFLOW result.
>>
>>             Thanks,
>>             Vladimir
>>
>>             On 1/9/13 3:58 AM, Ulf Zibis wrote:
>>
>>                 Am 09.01.2013 01:10, schrieb Vitaly Davidovich:
>>
>>                     On Jan 8, 2013 6:18 PM, "Vladimir Kozlov"
>>                     <vladimir.kozlov at oracle.com
>>                     <mailto:vladimir.kozlov@**oracle.com<vladimir.kozlov at oracle.com>
>> >>
>>                     wrote:
>>
>>                         http://cr.openjdk.java.net/~****
>> __kvn/6896617_jdk/webrev<http://cr.openjdk.java.net/~**__kvn/6896617_jdk/webrev>
>>                         <http://cr.openjdk.java.net/~***
>> *kvn/6896617_jdk/webrev<http://cr.openjdk.java.net/~**kvn/6896617_jdk/webrev>
>> ><http:**//__cr.openjdk.java.net/~kvn/_**_6896617_jdk/webrev<http://cr.openjdk.java.net/~kvn/__6896617_jdk/webrev>
>>                         <http://cr.openjdk.java.net/~**
>> kvn/6896617_jdk/webrev<http://cr.openjdk.java.net/~kvn/6896617_jdk/webrev>
>> >>
>>
>>
>>
>>                 Another tweak:
>>                    168             char[] sa = src.array();
>>                    169             int sp = src.arrayOffset() +
>>                 src.position();
>>                    170             int sr = src.remaining();
>>                    171             int sl = sp + sr;
>>                    172             assert (sp <= sl); // superfluous, sr
>>                 is always >= 0
>>                    173             sp = (sp <= sl ? sp : sl); //
>>                 superfluous "
>>                    174             byte[] da = dst.array();
>>                    175             int dp = dst.arrayOffset() +
>>                 dst.position();
>>                    170             int dr = dst.remaining();
>>                    176             int dl = dp + dr;
>>                    177             assert (dp <= dl); // superfluous   "
>>                    178             dp = (dp <= dl ? dp : dl); //
>>                 superfluous "
>>                    179             boolean overflow = false;
>>                    180             if (sr > dr) {
>>                    181                 sr = dr;
>>                    182                 overflow = true;
>>                    183             }
>>
>>                 Why you called it "overflowflag", in that way, you could
>>                 name each
>>                 variable "myvaluevariable" or "myvaluefield" ;-)
>>
>>
>>                 -Ulf
>>
>>
>>
>>
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