> -----Original Message-----
> From: Jeff Clites [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, January 07, 2004 12:52 AM
> To: Adam Thomason
> Cc: Internals List
> Subject: Re: [perl #24829] RE: [PATCH] PPC JIT fixes
> [re-send] (Modified
> by Jeff Clites)
>
> 1) In gdb, break on runops_jit, then step until jit_code is defined
> (but not jumpted to yet).
>
> 2) Dump the assembly by typing "x/40i jit_code". (That is "x" for
> examine memory at "jit_code", and the "/40i" says to format
> the output
> as instructions, and print out 40 of them.) That will at
> least give you
> the first chunk of the JIT-produced assembly.
>
> 3) Continue running. When you crash, use "info reg" to output the
> registers--the "pc" listed is the program counter, which should tell
> you the instruction on which you crashed. If the number
> matches one of
> the lines printed in (2), then that's where you crashed. If
> the number
> is in a completely different range, you probably jumped
> somewhere from
> the JIT code before crashing. If so, do (4):
The 40 ops range from 0x200fca28 to 0x200fca90, with 0x200fca94 onward being
".long 0x0". The pc at failure is 0x7c0802a4. So it's probably safe to
assume the trouble is pre-pasm.
> (4) Start over, but after step (2), instead of just continuing, step
> one instruction at a time with "nexti" until you crash. Each time you
> step it will print out the program counter, so you'll be able
> to see at
> which point you jump from the JIT code into the beginning-of-the-end.
> That will tell us at least where to start looking.
I'm seeing a bunch of different addresses, and I'm not totally sure what's
what. When the breakpoint hits, it says pc=0x200f7518, but the subsequent
disassembly shows runops_jit at 0x100313e0. Best I can gather, it's
attempting to branch to _ptrgl from runops_jit, but failing. Some googling
suggests that _ptrgl is a compiler-inserted routine for triggering indirect
function calls, which jives with the call into jit_code. I'm rather baffled
how pc becomes 0x7c0802a4 at the point of fault. See below for a transcript
of the gdb session.
> (Also, as a side note, I believe that before my patches the
> basic_1.pasm test was working on Mac OS X--about the only one
> working--so it may be that something completely different is going
> wrong on AIX. And actually, there's some
> flush-the-processor-cache code
> which may be conditionally compiled, so maybe that isn't building in
> your case, and your jump could end up trying to execute stale
> data. Or
> it may be and issue with calling convention differences
> between AIX and
> Mac OS X.)
One of the first things I did to get the port to work was introduce the
'#ifndef __IBMC__' guard in ppc_sync_cache in jit/ppc/jit_emit.h, just to get
the file to compile (xlC doesn't support any form of inlined asm). Might the
absence of the sync cause the trouble? If so, now is probably the time to
patch up the build system to support assembling a separate .s file containing
the necessary snippet. I can look into doing that, and calling it from
ppc_sync_cache, but I've no idea if there's any trouble w.r.t not inlining
that piece, so help would be appreciated.
Adam
------------------------------------------------------------------------------
gdb transcript, w/ some gratuitous whitespace:
GNU gdb 6.0
Copyright 2003 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "powerpc-ibm-aix4.3.3.0"...
(gdb) b src/interpreter.c:423
Breakpoint 1 at 0x10031404: file src/interpreter.c, line 423.
(gdb) r -d -j -v t/op/basic_1.pasm
Starting program: /auto/actinium-data01/thomason/parrot/working/parrot -d -j -v
t/op/basic_1.pasm
debug = 0x1
Reading t/op/basic_1.pasm
using optimization '0' (0)
Starting parse...
3 lines compiled.
Running...
*** Parrot VM: JIT core ***
*** Parrot VM: Setting up ARGV array in P5. Current argc: 1 ***
0: t/op/basic_1.pasm
Section:
NOT JITTED block 0
OP0: ext 1 noop
map_branch: 00
begin: 0x200f7518 (1)
end: 0x200f7518 (1)
I registers used: 0
N registers used: 0
Jit opcodes: 0
Total opcodes: 1
Section:
JITTED block 1
OP1: ext 0 end
map_branch: 00
begin: 0x200f751c (0)
end: 0x200f751c (0)
I registers used: 0
N registers used: 0
Jit opcodes: 1
Total opcodes: 1
Section:
NOT JITTED block 0
OP0: ext 1 noop
map_branch: 00
begin: 0x200f7518 (1)
end: 0x200f7518 (1)
I registers used: 0
N registers used: 0
Jit opcodes: 0
Total opcodes: 1
Section:
JITTED block 1
OP1: ext 0 end
map_branch: 00
begin: 0x200f751c (0)
end: 0x200f751c (0)
I registers used: 0
N registers used: 0
Jit opcodes: 1
Total opcodes: 1
Total size 108 bytes
Breakpoint 1, runops_jit (interpreter=0x20051438, pc=0x200f7518) at
src/interpreter.c:423
423 (jit_code) (interpreter, pc);
(gdb) x/30i jit_code
0x200fca28: mflr r0
0x200fca2c: stmw r13,-76(r1)
0x200fca30: stw r0,8(r1)
0x200fca34: stwu r1,-144(r1)
0x200fca38: xor r31,r31,r31
0x200fca3c: mr r13,r3
0x200fca40: lwz r12,768(r13)
0x200fca44: lwz r14,24(r12)
0x200fca48: lwz r12,748(r13)
0x200fca4c: lwz r15,220(r12)
0x200fca50: subf r12,r15,r4
0x200fca54: add r12,r14,r12
0x200fca58: lwz r12,0(r12)
0x200fca5c: mtctr r12
0x200fca60: bctrl
0x200fca64: ori r12,r31,0
0x200fca68: add r3,r15,r12
0x200fca6c: mr r4,r13
0x200fca70: ori r12,r31,26308
0x200fca74: oris r12,r12,8195
0x200fca78: mtctr r12
0x200fca7c: bctrl
0x200fca80: lwz r1,0(r1)
0x200fca84: lwz r0,8(r1)
0x200fca88: mtlr r0
0x200fca8c: lmw r13,-76(r1)
0x200fca90: blr
0x200fca94: .long 0x0
0x200fca98: .long 0x0
0x200fca9c: .long 0x0
(gdb) disass runops_jit
Dump of assembler code for function runops_jit:
0x100313e0 <runops_jit+0>: mflr r0
0x100313e4 <runops_jit+4>: stwu r1,-80(r1)
0x100313e8 <runops_jit+8>: stw r0,88(r1)
0x100313ec <runops_jit+12>: stw r3,104(r1)
0x100313f0 <runops_jit+16>: stw r4,108(r1)
0x100313f4 <runops_jit+20>: lwz r3,104(r1)
0x100313f8 <runops_jit+24>: lwz r4,108(r1)
0x100313fc <runops_jit+28>: bl 0x100329a4 <init_jit>
0x10031400 <runops_jit+32>: stw r3,64(r1)
0x10031404 <runops_jit+36>: lwz r3,104(r1)
0x10031408 <runops_jit+40>: lwz r4,108(r1)
0x1003140c <runops_jit+44>: lwz r11,64(r1)
0x10031410 <runops_jit+48>: bl 0x10001948 <_ptrgl>
0x10031414 <runops_jit+52>: lwz r2,20(r1)
0x10031418 <runops_jit+56>: li r3,0
0x1003141c <runops_jit+60>: b 0x10031420 <runops_jit+64>
0x10031420 <runops_jit+64>: lwz r0,88(r1)
0x10031424 <runops_jit+68>: mtlr r0
0x10031428 <runops_jit+72>: addi r1,r1,80
0x1003142c <runops_jit+76>: blr
0x10031430 <runops_jit+80>: .long 0x0
0x10031434 <runops_jit+84>: .long 0x2041
0x10031438 <runops_jit+88>: lwz r0,513(r0)
0x1003143c <runops_jit+92>: .long 0x0
0x10031440 <runops_jit+96>: .long 0x50
0x10031444 <runops_jit+100>: .long 0xa7275
0x10031448 <runops_jit+104>: xoris r15,r19,28787
0x1003144c <runops_jit+108>: rlwnm r10,r27,r13,5,26
End of assembler dump.
(gdb) nexti
0x10031408 423 (jit_code) (interpreter, pc);
(gdb) nexti
0x1003140c 423 (jit_code) (interpreter, pc);
(gdb) nexti
0x10031410 423 (jit_code) (interpreter, pc);
(gdb) nexti
Program received signal SIGSEGV, Segmentation fault.
0x7c0802a4 in ?? ()
(gdb) info reg
r0 0x7c0802a6 2080899750
r1 0x2ff222b0 804397744
r2 0xbda1ffb4 -1113456716
r3 0x20051438 537203768
r4 0x200f7518 537883928
r5 0x8 8
r6 0xa80 2688
r7 0x0 0
r8 0x10007167 268464487
r9 0x10007167 268464487
r10 0x200fce70 537906800
r11 0x90010008 -1878982648
r12 0x1008d318 269013784
r13 0xdeadbeef -559038737
r14 0x5 5
r15 0x2ff22560 804398432
r16 0x2ff22578 804398456
r17 0x200340cc 537084108
r18 0xdeadbeef -559038737
r19 0xdeadbeef -559038737
r20 0xdeadbeef -559038737
r21 0xdeadbeef -559038737
r22 0xdeadbeef -559038737
r23 0xdeadbeef -559038737
r24 0xdeadbeef -559038737
r25 0xdeadbeef -559038737
r26 0xdeadbeef -559038737
r27 0xdeadbeef -559038737
r28 0xdeadbeef -559038737
r29 0xdeadbeef -559038737
r30 0x101747f0 269961200
r31 0x200329b8 537078200
pc 0x7c0802a4 2080899748
ps 0x4000d0b0 1073795248
cr 0x22424044 574767172
lr 0x10031414 268637204
ctr 0x7c0802a6 2080899750
xer 0x20000000 536870912
fpscr 0x82024000 -2113781760
vscr 0x0 0
vrsave 0x0 0
(gdb) x/10i _ptrgl
0x10001948 <_ptrgl>: lwz r0,0(r11)
0x1000194c <_ptrgl+4>: stw r2,20(r1)
0x10001950 <_ptrgl+8>: mtctr r0
0x10001954 <_ptrgl+12>: lwz r2,4(r11)
0x10001958 <_ptrgl+16>: lwz r11,8(r11)
0x1000195c <_ptrgl+20>: bctr
0x10001960 <_ptrgl+24>: .long 0x0
0x10001964 <_ptrgl+28>: .long 0xca040
0x10001968 <_ptrgl+32>: .long 0x0
0x1000196c <_ptrgl+36>: .long 0x18
(gdb)
