Well, a few people confirmed that my suspected codegen bug was real,
and apparently still present in -current.  So I looked a bit deeper,
prompted largely by two reports that turning on the optimizer made the
crash (in the resulting compiled program) go away.

The problem is definitely a miscompilation of the nested function.  As
a reminder, the code in question looks like

	static int wrap(void (*fn)(unsigned char), unsigned char arg)
	{
	 __label__ fail;
	
	 static void _fail(void)
	  { goto fail;
	  }
[...]
	}

Unoptimized, this turns into

	.align 4
	.type	 __fail.4,@function
	.proc	020
__fail.4:
.stabn 68,0,12,LM1
LM1:
	!#PROLOGUE# 0
	save %sp,-112,%sp
	!#PROLOGUE# 1
	st %g2,[%fp-12]
.stabn 68,0,12,LM2
LM2:
	ta 3
	ld [%fp-16],%o0
	add %o0,8,%o1
	mov %o1,%fp
	sethi %hi(L6),%o1
	or %o1,%lo(L6),%o0
	ld [%fp-20],%fp
	ld [%fp-12],%g2
	jmp %o0+0
	restore

but optimized,

	.align 4
	.type	 __fail.4,@function
	.proc	020
__fail.4:
.stabn 68,0,12,LM1
LM1:
	!#PROLOGUE# 0
	save %sp,-112,%sp
	!#PROLOGUE# 1
	st %g2,[%fp-12]
	ta 3
	add %g2,8,%fp
	sethi %hi(L6),%o0
	or %o0,%lo(L6),%o0
	ld [%fp-16],%fp
	jmp %o0+0
	restore

Note that it appears that %fp should be loaded with 8 more than %g2 on
entry (since that's what the optimized - working - code does), but in
the unoptimized version, %g2 is stored to %fp-12 but the code that sets
%fp uses a value loaded from %fp-16.  The difference between %fp-20 and
%fp-16 later also looks suspicious, as if the compiler had managed to
get confused by 4 bytes about stackframe offsets.  (Note that when the
unoptimized code reloads %g2 before the jump, it loads it from the
correct place.)

Do we have anything NetBSD-specific in the SPARC egcs port, or is this
a real egcs bug?  I can compose a bug report for the gcc people, but
don't want to report a bug to them if it's really a bug in something
we've done; that doesn't make anyone look good. :-/

I'm currently trying to find out where the bug is, but I'm having to
teach myself gcc internals first....

					der Mouse

			       mouse@rodents.montreal.qc.ca
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