RFR(XXS): 8166767: C2: OptimizeStringConcat produces wrong results when copying UTF16 Strings

[Tobias Hartmann]

Hi Martin,

On 27.09.2016 11:40, Doerr, Martin wrote:
> Hi Tobias,
> 
> thank you very much for reviewing. You're right.
> I just noticed that the code didn't fit to another change which I have locally. I got to fix that.
> Sorry for the mistake. I'll close the bug.

Sure, no problem!

Best regards,
Tobias

> Best regards,
> Martin
> 
> 
> -----Original Message-----
> From: Tobias Hartmann [mailto:tobias.hartmann at oracle.com] 
> Sent: Dienstag, 27. September 2016 11:31
> To: Doerr, Martin <martin.doerr at sap.com>; hotspot-compiler-dev at openjdk.java.net
> Subject: Re: RFR(XXS): 8166767: C2: OptimizeStringConcat produces wrong results when copying UTF16 Strings
> 
> Hi Martin,
> 
> On 27.09.2016 11:03, Doerr, Martin wrote:
>> PhaseStringOpts::copy_constant_string increments index twice in the copy loop when source and destination are UTF16 encoded.
>> http://cr.openjdk.java.net/~mdoerr/8166767_StringOpts_copy_bug/webrev.00/ <http://cr.openjdk.java.net/%7Emdoerr/8166767_StringOpts_copy_bug/webrev.00/>
> 
> The index passed to readChar refers to an index in the source byte array (and length is the size in bytes):
>  // Read two bytes from index and index+1 and convert them to a char
> 
> For example, if we want to read the second char value, we need to use index = 4. Therefore, if we read chars, we need to increment i twice in each loop iteration to get the correct char index in the byte array.
> 
> Or am I missing something?
> 
> Best regards,
> Tobias
>