JDK-8239787 : AArch64: String.indexOf may incorrectly handle empty strings

[Yuri Nesterenko]

/Hi Alexey, could you please provide a regression test with this fix?
Thanks, --yan >Hello Andrew, > >Can we commit this fix into JDK15 and
set backport flags to JDK9 and higher? >As soon as it is simple fix and
applied cleanly to all JDK versions (starting from JDK9) we can backport
it to all applicable versions as well. > >Thank you >Alexey > >> On 27
Feb 2020, at 13:42, Alexey Bakhtin <alexey at azul.com> wrote: >> >>
Hello Andrew, >> >> Thank you for review. >> string_indexof_char
intrinsic for aarch64 was introduced in JDK9 ( JDK-8157708 ), so this
patch is applicable to JDK9 and higher. >> JDK8 does not support
string_indexof_char intrinsic, so does not have this issue. >> >> Thank
you >> Alexey >> >>> On 26 Feb 2020, at 20:39, Andrew Haley <aph at
redhat.com> wrote: >>> >>> Hi, >>> >>> On 2/26/20 12:51 PM, Alexey
Bakhtin wrote: >>>> Could you please review fix for aarch64 related
issue: https://bugs.openjdk.java.net/browse/JDK-8239787 >>>> >>>> The
fix verifies length of the string at the beginning of
string_indexof_char intrinsic code : >>>> >>>> diff --git
a/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp >>>>
b/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp >>>> ---
a/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp >>>> +++
b/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp >>>> @@ -4860,6
+4860,8 @@ >>>> Register ch1 = rscratch1; >>>> Register result_tmp =
rscratch2; >>>> >>>> + cbz(cnt1, NOMATCH); >>>> + >>>> cmp(cnt1, (u1)4);
>>>> br(LT, DO1_SHORT); >>> >>> Looks good, thanks. Can you please have
a look at JDK 8u and 11u, to see >>> if the bug is there too? Then we
can set backport flags. >>> >>> The 8u repo is at >>>
http://hg.openjdk.java.net/aarch64-port/jdk8u-shenandoah/hotspot/ >>>
>>> -- >>> Andrew Haley (he/him) >>> Java Platform Lead Engineer >>> Red
Hat UK Ltd. <https://www.redhat.com> >>> https://keybase.io/andrewhaley
>>> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671/