bootcheck failed -- stage 2 & 3 differ

[Fergus Henderson]

Hi,

The nightly tests on murlibobo failed tonight.
They last succeeded just last night, so the
problem must have been due to something checked 
in on Monday (between 12:30am Monday and 12:30am Tuesday).

The symptom is a difference between the stage 2 and stage 3
compilers:

--- stage2/compiler/bytecode_data.c	Tue Mar 23 01:28:25 1999
+++ stage3/compiler/bytecode_data.c	Tue Mar 23 01:59:15 1999
@@ -471,7 +471,7 @@
 	update_prof_current_proc(LABEL(mercury__bytecode_data__output_int_3_0));
 	if (((Integer) 64 >= (Integer) r1))
 		GOTO_LABEL(mercury__bytecode_data__output_int_3_0_i7);
-	r2 = ((Integer) MR_stackvar(1) & (Integer) -1);
+	r2 = ((Integer) MR_stackvar(1) & (Integer) 0);
 	if (((Integer) r2 == (Integer) 0))
 		GOTO_LABEL(mercury__bytecode_data__output_int_3_0_i7);
 	tag_incr_hp_msg(r2, mktag(1), (Integer) 2, mercury__bytecode_data__output_int_3_0, "origin_lost_in_value_number");

The cause of this is Simon's changes to << and >>.
The line which is being compiled differently is this one,

	(IntVal /\ (\0 << Bits)) \= 0

from line 144 of bytecode.m, where the compiler has
(though inlining) been able to figure out that Bits
has the value 64.  And \0 is of course just -1.
So the value which is being compiled to either -1 or 0
is `-1 << 64'.  This ought to evaluate to 0, not -1,
so the stage 3 compiler is in fact correct, and it is
the stage 2 compiler which is wrong.

So, I think the solution to this is to ignore the error, install the
compiler anyway, and the problem should go away.  I will make a
temporary modification to the copy of the test_mercury script in
/home/mercury/public/test_mercury/scripts to ensure that this happens.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
WWW: <http://www.cs.mu.oz.au/~fjh>  |  of excellence is a lethal habit"
PGP: finger fjh at 128.250.37.3        |     -- the last words of T. S. Garp.