On Tue, 14 Nov 2023 16:05:51 GMT, Roger Riggs <rri...@openjdk.org> wrote:

>> Strings, after construction, are immutable but may be constructed from 
>> mutable arrays of bytes, characters, or integers.
>> The string constructors should guard against the effects of mutating the 
>> arrays during construction that might invalidate internal invariants for the 
>> correct behavior of operations on the resulting strings. In particular, a 
>> number of operations have optimizations for operations on pairs of latin1 
>> strings and pairs of non-latin1 strings, while operations between latin1 and 
>> non-latin1 strings use a more general implementation. 
>> 
>> The changes include:
>> 
>> - Adding a warning to each constructor with an array as an argument to 
>> indicate that the results are indeterminate 
>>   if the input array is modified before the constructor returns. 
>>   The resulting string may contain any combination of characters sampled 
>> from the input array.
>> 
>> - Ensure that strings that are represented as non-latin1 contain at least 
>> one non-latin1 character.
>>   For latin1 inputs, whether the arrays contain ASCII, ISO-8859-1, UTF8, or 
>> another encoding decoded to latin1 the scanning and compression is unchanged.
>>   If a non-latin1 character is found, the string is represented as 
>> non-latin1 with the added verification that a non-latin1 character is 
>> present at the same index.
>>   If that character is found to be latin1, then the input array has been 
>> modified and the result of the scan may be incorrect.
>>   Though a ConcurrentModificationException could be thrown, the risk to an 
>> existing application of an unexpected exception should be avoided.
>>   Instead, the non-latin1 copy of the input is re-scanned and compressed; 
>> that scan determines whether the latin1 or the non-latin1 representation is 
>> returned.
>> 
>> - The methods that scan for non-latin1 characters and their intrinsic 
>> implementations are updated to return the index of the non-latin1 character.
>> 
>> - String construction from StringBuilder and CharSequence must also be 
>> guarded as their contents may be modified during construction.
>
> Roger Riggs has updated the pull request incrementally with one additional 
> commit since the last revision:
> 
>   Update PPC implementation of string_compress to return the index of the 
> non-latin1 char
>   Patch supplied by TheRealMDoerr

src/hotspot/cpu/x86/macroAssembler_x86.cpp line 8617:

> 8615:     lea(dst, Address(dst, tmp5, Address::times_1));
> 8616:     subptr(len, tmp5);
> 8617:     jmpb(copy_chars_loop);

This cause a crash if I run with `-XX:UseAVX=3 -XX:AVX3Threshold=0`:


#
# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error (macroAssembler_x86.hpp:122), pid=3400452, tid=3400470
#  guarantee(this->is8bit(imm8)) failed: Short forward jump exceeds 8-bit 
offset at <null>:0
#


Needs to be a `jmp(copy_chars_loop)`.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/16425#discussion_r1394375402

Reply via email to