Re: Weird problem

[David Malcolm <dmalcolm@redhat.com>]

On Mon, 2015-06-29 at 22:25 +0100, Dibyendu Majumdar wrote:
> On 29 June 2015 at 22:08, David Malcolm <dmalcolm@redhat.com> wrote:
> 
> > Looking at src/lvm.c, I see that the signature of luaV_tonumber and that
> > lua_Number can be various types, including "double".
> >   int luaV_tonumber_ (const TValue *obj, lua_Number *n)
> >
> 
> I am using double as lua_Number.
> 
> > Does the type signature of luaV_tonumber as compiled by the main
> > compiler agree with that supplied by gcc_jit_context_new_function?  If
> > one of them is e.g. expecting a float *, but the other is expecting a
> > double *, then you might get the symptoms you're seeing.
> >
> 
> I checked this - I think they match.
> 
> > If that doesn't highlight a cause, maybe you're running into a libgccjit
> > bug.  If so, can you generate a reproducer and post it here so I can
> > poke at it please?
> >
> 
> Attached is a reproducer.

Thanks; I'm able to run the reproducer, at least to the point of being
able to invoke gcc_jit_context_compile on it.

Interestingly, looking at the gimple dump (via
GCC_JIT_BOOL_OPTION_DUMP_INITIAL_GIMPLE), I see:

  <float:64> OP_RAVI_TOFLT_n_2_8.0;
  <float:64> OP_RAVI_TOFLT_n_2_8.1;
  [...snip...]
  <float:64> OP_RAVI_TOFLT_n_2_8;
  [...snip...]

OP_RAVI_TOFLT_if_not_float_2_10:
  OP_RAVI_TOFLT_n_2_8.0 = OP_RAVI_TOFLT_n_2_8;
  printf ("number %p = %f before call to luaV_number",
&OP_RAVI_TOFLT_n_2_8.0, OP_RAVI_TOFLT_n_2_8);
  OP_RAVI_TOFLT_n_2_8.1 = OP_RAVI_TOFLT_n_2_8;
  [...snip...]
  OP_RAVI_TOFLT_n_2_8.1 = OP_RAVI_TOFLT_n_2_8;
  D.392 = 0;
  D.393 = base + D.392;
  D.405 = luaV_tonumber_ (D.393, &OP_RAVI_TOFLT_n_2_8.1);
          ^^^^^^^^^^^^^^ here's the call          ^^^^^
  comparison_0_12 = D.405 == 0;
  if (comparison_0_12 != 0) goto
OP_RAVI_TOFLT_if_conversion_failed_2_13; else goto
OP_RAVI_TOFLT_if_conversion_ok_2_14;

OP_RAVI_TOFLT_done_2_11:
  D.390 = L->ci;
  base = D.390->u.l.base;
  D.399 = 16;
  D.400 = base + D.399;
  L->top = D.400;
  D.394 = cl->p;
  D.406 = D.394->sizep;
  comparison_0_15 = D.406 > 0;
  if (comparison_0_15 != 0) goto OP_RETURN_if_sizep_gt_0_3_16; else goto
OP_RETURN_else_sizep_gt_0_3_17;

OP_RAVI_TOFLT_if_conversion_failed_2_13:
  luaG_runerror (L, "number expected");
  goto OP_RAVI_TOFLT_if_conversion_ok_2_14;
  OP_RAVI_TOFLT_if_conversion_ok_2_14:
  printf ("number ok = %f", OP_RAVI_TOFLT_n_2_8);

  [...snip...]

which, if I'm reading it right, suggests that the local has effectively
been split into three locals during the conversion to gimple, and that a
ptr to
  OP_RAVI_TOFLT_n_2_8.1
is passed to luaV_tonumber_, but
  OP_RAVI_TOFLT_n_2_8
is then used.

This is feeling like a bug at my end; sorry.  I'll continue to
investigate.