[kaffe] Release 1.0.7: Deadlock in JIT3 (Amiga m68k)
Tony Wyatt
wyattaw at optushome.com.au
Sat Jun 21 04:20:02 PDT 2003
Hi all,
While I can't get Release 1.1.0 to compile, I just had a little play with
1.0.7-JIT3. I have a test program that causes a deadlock when run, due to a
corrupted Lock address.
The program is:
"import java.io.*;
class FloatTest
{
public static void main(String[] args)
{
System.out.println("=" + (fmeth() / fmeth()) );
}
public static float fmeth()
{
return 0.0f;
}
}
"
The temporary result for the division within the println call causes the
problem.
The translated Method code for FloatTest.main generates the following code
which over-writes the address of the Lock variable (my comments):
L0: 1
@0: getstatic 12
@3: new 15
@6: dup
@7: ldc1 17
@9: invokespecial 22
@12: invokestatic 26
@15: invokestatic 26
@18: fdiv
@19: invokevirtual 30
@22: invokevirtual 34
@25: invokevirtual 37
@28: return
0000: linkw %fp, #0
- - -
002a: jsr +0 // soft_new
0030: addql #4, %sp
0032: movel %d0, -12(%fp) // save result
- - -
009a: fsmoves -8(%fp), %fp1
00a0: fsdivx %fp0, %fp1
00a4: fmoved %fp1, -12(%fp) // destroys saved Lock
- - -
00ce: movel 12(%fp), -(%sp)
00d2: movel -8(%fp), -(%sp)
00d6: movel -12(%fp), -(%sp)
00da: moveal #0x8e0713e, %a0 // "append"
00e0: moveal (%a0), %a0
00e2: jsr (%a0)
If I alter the source to write the floating result into a local variable,
the deadlock does not occur:
"import java.io.*;
class FloatTest
{
public static void main(String[] args)
{
float result = (fmeth() / fmeth());
System.out.println("=" + result );
}
public static float fmeth()
{
return 0.0f;
}
}
"
The new resulting code is:
L0: 1 L1: 1
@0: invokestatic 12
@3: invokestatic 12
@6: fdiv
@7: fstore 1
@8: getstatic 16
@11: new 19
@14: dup
@15: ldc1 21
@17: invokespecial 26
@20: fload 1
@21: invokevirtual 30
@24: invokevirtual 34
@27: invokevirtual 37
@30: return
0000: linkw %fp, #0
- - -
0046: fsdivx %fp0, %fp1 // do the division
004a: fsmovex %fp1, %fp0
- - -
005a: fmoves %fp0, -4(%fp) // save FP result
- - -
0066: jsr +0 // soft_new
006c: addql #4, %sp
006e: movel %d0, -16(%fp) // save result
- - -
00ac: fsmoves -4(%fp), %fp0 // a little nonsense
00b2: fsmovex %fp0, %fp1 // to keep the
00b6: fmoves %fp1, -12(%fp) // FPU warm
- - -
00e0: movel 12(%fp), -(%sp)
00e4: movel -12(%fp), -(%sp)
00e8: movel -16(%fp), -(%sp)
00ec: moveal #0x938313e, %a0 // "append"
00f2: moveal (%a0), %a0
00f4: jsr (%a0)
Needless to say, this version runs without deadlocking. My question is,
where should I start looking for the problem in the first version? In the area
of "register spillage"? In the area of "save temporary variables"? I could
do with a hint, please.
cheers
tony
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