The picture that made my day!
Ok.. so what happened?
xerxes@babbage-karmic:/wd/icedtea6/openjdk/build/linux-arm/bin$ ./java -version
java version "1.6.0_0"
OpenJDK Runtime Environment (IcedTea6 1.7pre-r2a3725ce72d4) (build 1.6.0_0-b16)
OpenJDK Shark VM (build 14.0-b16-product, mixed mode)
xerxes@babbage-karmic:/wd/icedtea6/openjdk/build/linux-arm/bin$ cat /proc/cpuinfo
Processor : ARMv7 Processor rev 1 (v7l)
BogoMIPS : 799.53
Features : swp half thumb fastmult vfp edsp
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x2
CPU part : 0xc08
CPU revision : 1
Hardware : Freescale MX51 Babbage Board
Revision : 51011
Serial : 0000000000000000
xerxes@babbage-karmic:/wd/llvm$ svn info
URL: http://llvm.org/svn/llvm-project/llvm/trunk
Repository Root: http://llvm.org/svn/llvm-project
Repository UUID: 91177308-0d34-0410-b5e6-96231b3b80d8
Revision: 82896
Node Kind: directory
Schedule: normal
Last Changed Author: edwin
Last Changed Rev: 82896
Last Changed Date: 2009-09-27 11:08:03 +0000 (Sun, 27 Sep 2009)
xerxes@babbage-karmic:/wd/llvm$ quilt diff
Index: llvm/lib/Target/ARM/ARMInstrInfo.td
===================================================================
--- llvm.orig/lib/Target/ARM/ARMInstrInfo.td 2009-10-06 12:35:26.000000000 +0000
+++ llvm/lib/Target/ARM/ARMInstrInfo.td 2009-10-06 12:36:03.000000000 +0000
@@ -645,7 +645,7 @@
IIC_Br, "mov lr, pc\n\tbx $func",
[(ARMcall_nolink GPR:$func)]>,
Requires<[IsARM, IsNotDarwin]> {
- let Inst{7-4} = 0b0001;
+ let Inst{7-4} = 0b0011;
let Inst{19-8} = 0b111111111111;
let Inst{27-20} = 0b00010010;
}
The last patch on LLVM are currently a hack. basically it makes LLVM emit ARM BLX instructions instead of BX instructions for ARM::CALL_NOLINK. So why did this little hack make it work?
In order to understand that, one have to find out what made Shark on ARM crash before…
Lets rewind time to some days ago...
Hi, i have been enjoying myself inside gdb for some days, and I have now at least found the reason why the cpu
ends up in garbage memory when running shark on arm.
The problem can be illustrated like this:
frame manager invokes jited code
entry_zero.hpp:57 invokes jit code at 0x67c9e990
jited code runs
0x67c9e990: push {r4, r5, r6, r7, r8, r9, r10, r11, lr}
0x67c9e994: sub sp, sp, #12 ; 0xc
0x67c9e998: ldr r12, [r3, #756]
0x67c9e99c: ldr lr, [r3, #764]
0x67c9e9a0: sub r4, lr, #56 ; 0x38
0x67c9e9a4: cmp r4, r12
0x67c9e9a8: bcc 0x67c9ebd0
0x67c9e9ac: mov r5, r3
0x67c9e9b0: str r2, [sp, #4]
0x67c9e9b4: mov r6, r0
0x67c9e9b8: str r4, [r5, #764]
0x67c9e9bc: str r4, [r4, #20]
0x67c9e9c0: ldr r0, [pc, #640] ; 0x67c9ec48
0x67c9e9c4: str r0, [r4, #28]
0x67c9e9c8: ldr r0, [r5, #768]
0x67c9e9cc: str r0, [r4, #32]
0x67c9e9d0: add r0, r4, #32 ; 0x20
0x67c9e9d4: str r0, [r5, #768]
0x67c9e9d8: str r6, [r4, #16]
0x67c9e9dc: ldr r7, [r1]
0x67c9e9e0: ldr r0, [r1, #4]
0x67c9e9e4: str r0, [sp]
0x67c9e9e8: ldr r8, [r1, #8]
0x67c9e9ec: ldr r9, [r1, #12]
0x67c9e9f0: ldr r0, [r1, #16]
0x67c9e9f4: str r0, [sp, #8]
0x67c9e9f8: ldr r10, [r1, #20]
0x67c9e9fc: ldr r2, [pc, #584] ; 0x67c9ec4c <------ jit code calls a jvm function stored in this address
0x67c9ea00: mov r0, r1
0x67c9ea04: bx r2 <--------------------------- problem! should have been blx!
(gdb) x 0x67c9ec4c
0x67c9ec4c: 0x40836d9c
(gdb) x 0x40836d9c
0x40836d9c <_ZN13SharedRuntime17OSR_migration_endEPi>: 0xe92d41f0
(gdb)
so lets check out _ZN13SharedRuntime17OSR_migration_endEPi
0x40836d9c <_ZN13SharedRuntime17OSR_migration_endEPi+0>: push {r4, r5, r6, r7, r8, lr} <------ lr are backed up.. but bx did not update lr..
0x40836da0 <_ZN13SharedRuntime17OSR_migration_endEPi+4>: ldr r4, [pc, #284] ; 0x40836ec4 <_ZN13SharedRuntime17OSR_migration_endEPi+296>
0x40836da4 <_ZN13SharedRuntime17OSR_migration_endEPi+8>: ldr r7, [pc, #284] ; 0x40836ec8 <_ZN13SharedRuntime17OSR_migration_endEPi+300>
0x40836da8 <_ZN13SharedRuntime17OSR_migration_endEPi+12>: ldr r6, [pc, #284] ; 0x40836ecc <_ZN13SharedRuntime17OSR_migration_endEPi+304>
0x40836dac <_ZN13SharedRuntime17OSR_migration_endEPi+16>: add r4, pc, r4
0x40836db0 <_ZN13SharedRuntime17OSR_migration_endEPi+20>: ldr r12, [r4, r7]
0x40836db4 <_ZN13SharedRuntime17OSR_migration_endEPi+24>: ldr r1, [r4, r6]
0x40836db8 <_ZN13SharedRuntime17OSR_migration_endEPi+28>: ldr r5, [r12]
0x40836dbc <_ZN13SharedRuntime17OSR_migration_endEPi+32>: ldrb r2, [r1]
0x40836dc0 <_ZN13SharedRuntime17OSR_migration_endEPi+36>: add r3, r5, #1 ; 0x1
0x40836dc4 <_ZN13SharedRuntime17OSR_migration_endEPi+40>: cmp r2, #0 ; 0x0
0x40836dc8 <_ZN13SharedRuntime17OSR_migration_endEPi+44>: sub sp, sp, #24 ; 0x18
0x40836dcc <_ZN13SharedRuntime17OSR_migration_endEPi+48>: str r3, [r12]
0x40836dd0 <_ZN13SharedRuntime17OSR_migration_endEPi+52>: mov r7, r0
0x40836dd4 <_ZN13SharedRuntime17OSR_migration_endEPi+56>: bne 0x40836e74 <_ZN13SharedRuntime17OSR_migration_endEPi+216>
0x40836dd8 <_ZN13SharedRuntime17OSR_migration_endEPi+60>: ldr r2, [pc, #240] ; 0x40836ed0 <_ZN13SharedRuntime17OSR_migration_endEPi+308>
0x40836ddc <_ZN13SharedRuntime17OSR_migration_endEPi+64>: ldr r12, [r4, r2]
0x40836de0 <_ZN13SharedRuntime17OSR_migration_endEPi+68>: ldrb r3, [r12]
0x40836de4 <_ZN13SharedRuntime17OSR_migration_endEPi+72>: cmp r3, #0 ; 0x0
0x40836de8 <_ZN13SharedRuntime17OSR_migration_endEPi+76>: beq 0x40836e20 <_ZN13SharedRuntime17OSR_migration_endEPi+132>
0x40836dec <_ZN13SharedRuntime17OSR_migration_endEPi+80>: ldr r6, [pc, #224] ; 0x40836ed4 <_ZN13SharedRuntime17OSR_migration_endEPi+312>
0x40836df0 <_ZN13SharedRuntime17OSR_migration_endEPi+84>: ldr r5, [r4, r6]
0x40836df4 <_ZN13SharedRuntime17OSR_migration_endEPi+88>: add r0, r4, r6
0x40836df8 <_ZN13SharedRuntime17OSR_migration_endEPi+92>: tst r5, #1 ; 0x1
0x40836dfc <_ZN13SharedRuntime17OSR_migration_endEPi+96>: beq 0x40836e8c <_ZN13SharedRuntime17OSR_migration_endEPi+240>
0x40836e00 <_ZN13SharedRuntime17OSR_migration_endEPi+100>: ldr r5, [pc, #208] ; 0x40836ed8 <_ZN13SharedRuntime17OSR_migration_endEPi+316>
0x40836e04 <_ZN13SharedRuntime17OSR_migration_endEPi+104>: ldr r3, [r4, r5]
0x40836e08 <_ZN13SharedRuntime17OSR_migration_endEPi+108>: cmp r3, #0 ; 0x0
0x40836e0c <_ZN13SharedRuntime17OSR_migration_endEPi+112>: movne r0, r3
0x40836e10 <_ZN13SharedRuntime17OSR_migration_endEPi+116>: ldrne r6, [r3]
0x40836e14 <_ZN13SharedRuntime17OSR_migration_endEPi+120>: ldrne r12, [r6, #16]
0x40836e18 <_ZN13SharedRuntime17OSR_migration_endEPi+124>: movne lr, pc
0x40836e1c <_ZN13SharedRuntime17OSR_migration_endEPi+128>: bxne r12
0x40836e20 <_ZN13SharedRuntime17OSR_migration_endEPi+132>: add r6, sp, #20 ; 0x14
0x40836e24 <_ZN13SharedRuntime17OSR_migration_endEPi+136>: mov r0, r6
0x40836e28 <_ZN13SharedRuntime17OSR_migration_endEPi+140>: bl 0x40596c84 <NoHandleMark>
0x40836e2c <_ZN13SharedRuntime17OSR_migration_endEPi+144>: mov r0, sp
0x40836e30 <_ZN13SharedRuntime17OSR_migration_endEPi+148>: bl 0x4057909c <JRT_Leaf_Verifier>
0x40836e34 <_ZN13SharedRuntime17OSR_migration_endEPi+152>: ldr r3, [pc, #160] ; 0x40836edc <_ZN13SharedRuntime17OSR_migration_endEPi+320>
0x40836e38 <_ZN13SharedRuntime17OSR_migration_endEPi+156>: mov r5, sp
0x40836e3c <_ZN13SharedRuntime17OSR_migration_endEPi+160>: ldr r12, [r4, r3]
0x40836e40 <_ZN13SharedRuntime17OSR_migration_endEPi+164>: ldrb r0, [r12]
0x40836e44 <_ZN13SharedRuntime17OSR_migration_endEPi+168>: cmp r0, #0 ; 0x0
0x40836e48 <_ZN13SharedRuntime17OSR_migration_endEPi+172>: movne r0, r7
0x40836e4c <_ZN13SharedRuntime17OSR_migration_endEPi+176>: blne 0x4039b20c <_Z15trace_heap_freePv>
0x40836e50 <_ZN13SharedRuntime17OSR_migration_endEPi+180>: mov r0, r7
0x40836e54 <_ZN13SharedRuntime17OSR_migration_endEPi+184>: bl 0x407b6a94 <_ZN2os4freeEPv>
0x40836e58 <_ZN13SharedRuntime17OSR_migration_endEPi+188>: mov r0, sp
0x40836e5c <_ZN13SharedRuntime17OSR_migration_endEPi+192>: bl 0x40578c5c <~JRT_Leaf_Verifier>
0x40836e60 <_ZN13SharedRuntime17OSR_migration_endEPi+196>: mov r0, r6
0x40836e64 <_ZN13SharedRuntime17OSR_migration_endEPi+200>: bl 0x40596b04 <~NoHandleMark>
0x40836e68 <_ZN13SharedRuntime17OSR_migration_endEPi+204>: add sp, sp, #24 ; 0x18
0x40836e6c <_ZN13SharedRuntime17OSR_migration_endEPi+208>: pop {r4, r5, r6, r7, r8, lr}
0x40836e70 <_ZN13SharedRuntime17OSR_migration_endEPi+212>: bx lr <------ and woho. lets enjoy a trip to garbage memory!
So when the function that the jit calls returns we find ourself eating
garbage memory.
So the small hack fixed this issue quite well but broke armv4t compatibility for the moment.
My next task would be to fix this properly in LLVM.
Congrats Xerxes!
This is great day for Java-enabled ARM + GNU/Linux netbooks and other gadgets.
Comment by Robert Schuster — October 6, 2009 @ 4:55 pm
Xerxes, that’s awesome! Following your shark trailblazing with great interest.
Comment by Ken Gilmer — October 6, 2009 @ 5:45 pm
Congrats! Really cool!
Looking foreward to run shark on my armv5tje based 770 soon
Comment by Clemens Eisserer — October 6, 2009 @ 11:12 pm
Yep, I’m looking forward to jumping (on the) Shark!
Good work.
Rgds
Damon
Comment by Damon Hart-Davis — October 7, 2009 @ 6:29 pm
Thank you all for your parts as well!
Robert and Ken:, the initial work you two made to enable quick cross-compile builds of OpenJDK have helped me enormously to make me able to quickly test and generate debug builds of Shark.
Clemens: Thank you for your work as well on the XRender backends to speeding up the Swing GUI operations, you work really makes a difference for Client GUI performance on ARM!
For you who dont know about Clemens XRender work check out: http://linuxhippy.blogspot.com/ and try run your favourite application with java -Dsun.java2d.xrender=True my.fancy.gui.HelloWorld its cool!
Damon: Hey, your work with running a green power efficient server running tomcat on a Sheevaplug are a true green computing future gem!
Checkout Damons notes on how to make a 1-5w main internet facing server running on ARM: http://www.earth.org.uk/note-on-SheevaPlug-setup.html
Clemens and Damon: The Jalimo cross compile work that I also have recently been involved in together with Ken and Robert will surely produce some cool binarys for you to use on your armv5tel maemo phone and sheeva plug. I plan to publish some binarys for testing somewhere during next week.
The Jalimo project can be checked out at: http://evolvis.org/projects/jalimo
Comment by xerxes — October 9, 2009 @ 1:51 pm