PrintAssembly at runtime / to different target

[Stefan Reich]

Hmm. I built JDK 13 from Mercurial with fastdebug, and it always sends
assembly output to tty.

root at vmd41736:~/dev/ii-assembly# java13-dbg -version
openjdk version "13-internal" 2019-09-17
OpenJDK Runtime Environment (fastdebug build 13-internal+0-adhoc.root.jdk13)
OpenJDK 64-Bit Server VM (fastdebug build 13-internal+0-adhoc.root.jdk13,
mixed mode)
root at vmd41736:~/dev/ii-assembly# java13-dbg -XX:+UnlockDiagnosticVMOptions
-XX:+LogCompilation -XX:+PrintAssembly -jar ~/.javax/x30.jar -noawt 1025248
>ii-assembly.out
OpenJDK 64-Bit Server VM warning: PrintAssembly is enabled; turning on
DebugNonSafepoints to gain additional output
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by x30 (file:/root/.javax/x30.jar) to
method java.lang.Object.registerNatives()
WARNING: Please consider reporting this to the maintainers of x30
WARNING: Use --illegal-access=warn to enable warnings of further illegal
reflective access operations
WARNING: All illegal access operations will be denied in a future release
root at vmd41736:~/dev/ii-assembly# java13-dbg -XX:+UnlockDiagnosticVMOptions
-XX:+LogCompilation -XX:+PrintAssembly -jar ~/.javax/x30.jar -noawt 1025248
>hotspot.out
OpenJDK 64-Bit Server VM warning: PrintAssembly is enabled; turning on
DebugNonSafepoints to gain additional output
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by x30 (file:/root/.javax/x30.jar) to
method java.lang.Object.registerNatives()
WARNING: Please consider reporting this to the maintainers of x30
WARNING: Use --illegal-access=warn to enable warnings of further illegal
reflective access operations
WARNING: All illegal access operations will be denied in a future release
root at vmd41736:~/dev/ii-assembly# ls -ltrh
total 184M
-rw-r--r-- 1 root root  42M Sep 16 18:26 hotspot.out
-rw-r--r-- 1 root root  46M Sep 16 18:26 hotspot_pid15548.log
root at vmd41736:~/dev/ii-assembly# grep mov hotspot.out
hotspot_pid15548.log|head -5
hotspot.out: ;; move 0 -> 2
hotspot.out:000     movl    rscratch1, [j_rarg0 +
oopDesc::klass_offset_in_bytes()] # compressed klass
hotspot.out: movq    rscratch1, poll_offset[r15_thread]
#polling_page_address
hotspot.out:000     movl    rscratch1, [j_rarg0 +
oopDesc::klass_offset_in_bytes()] # compressed klass
hotspot.out:02c     movsbl  R10, [RSI + #20 (8-bit)] # byte ! Field:
java/lang/String.coder (constant)

On Mon, 16 Sep 2019 at 18:24, Aleksey Shipilev <shade at redhat.com> wrote:

> On 9/16/19 6:18 PM, Stefan Reich wrote:
> > How can I get assembly output in hotspot.log though? I only ever see it
> on STDOUT, even with
> > LogCompilation enabled.
>
> LogCompilation has to include output that would otherwise would end up on
> tty. It would be captured
> in <tty> there.
>
> JMH -prof perfasm does use LogCompilation to get disassembly like this:
>
> http://hg.openjdk.java.net/code-tools/jmh/file/99d7b73cf1e3/jmh-core/src/main/java/org/openjdk/jmh/profile/AbstractPerfAsmProfiler.java#l239
>
> --
> Thanks,
> -Aleksey
>
>

-- 
Stefan Reich
BotCompany.de // Java-based operating systems