On Mon, 14 Sep 2015, Richard Biener wrote:
> On Sat, 12 Sep 2015, Eric Botcazou wrote:
>
> > > * fold-const.c (fold_binary_loc): Move simplifying of comparisons
> > > against the highest or lowest possible integer ...
> > > * match.pd: ... as patterns here.
> >
> > This incorrectly dropped the calls to omit_one_operand_loc, resulting in
> > the
> > failure of the attached Ada test: if the operand has side effects, you
> > cannot
> > replace the entire comparison with just 'true' or 'false'.
>
> Still trying to reproduce, but I suppose you hit
>
> /* Comparisons with the highest or lowest possible integer of
> the specified precision will have known values. */
> (simplify
> (cmp (convert?@2 @0) INTEGER_CST@1)
> (if ((INTEGRAL_TYPE_P (TREE_TYPE (@1)) || POINTER_TYPE_P (TREE_TYPE
> (@1)))
> && tree_nop_conversion_p (TREE_TYPE (@2), TREE_TYPE (@0)))
> (with
> {
> tree arg1_type = TREE_TYPE (@1);
> unsigned int prec = TYPE_PRECISION (arg1_type);
> wide_int max = wi::max_value (arg1_type);
> wide_int signed_max = wi::max_value (prec, SIGNED);
> wide_int min = wi::min_value (arg1_type);
> }
> (switch
> (if (wi::eq_p (@1, max))
> (switch
> (if (cmp == GT_EXPR)
> { constant_boolean_node (false, type); })
> (if (cmp == GE_EXPR)
> (eq @2 @1))
> (if (cmp == LE_EXPR)
> { constant_boolean_node (true, type); })
>
> this which should handle side-effects in @0 just fine:
>
> /* #line 2019 "/space/rguenther/src/svn/trunk/gcc/match.pd" */
> if (cmp == LE_EXPR)
> {
> if (dump_file && (dump_flags & TDF_DETAILS))
> fprintf (dump_file, "Applying pattern match.pd:2020, %s:%d\n", __FILE__,
> __LINE__);
> tree res;
> res = constant_boolean_node (true, type);
> if (TREE_SIDE_EFFECTS (captures[0]))
> res = build2_loc (loc, COMPOUND_EXPR, type,
> fold_ignored_result (captures[0]), res);
> return res;
>
> note that genmatch "inlines" omit_one_operand, so you only see
> fold_ignored_result here.
>
> So maybe the issue is with some other pattern or was latent
> elsewehere. I'll have a closer look once I manage to reproduce
> the issue.
Ok, so it's folding
x == 127 ? .gnat_rcheck_CE_Overflow_Check ("overflow_sum3.adb", 14);, 0 :
(short_short_integer) x + 1
<= 127
where op0 (the COND_EXPR) does not have TREE_SIDE_EFFECTS set but
its operand 1 has:
(gdb) p debug_tree (op0)
<cond_expr 0x7ffff68cbf90
type <integer_type 0x7ffff6572dc8 short_short_integer sizes-gimplified
public visited QI
size <integer_cst 0x7ffff68ccca8 constant visited 8>
unit size <integer_cst 0x7ffff68cccc0 constant visited 1>
align 8 symtab 0 alias set -1 canonical type 0x7ffff6572dc8
precision 8 min <integer_cst 0x7ffff656a678 -128> max <integer_cst
0x7ffff656a6c0 127> context <translation_unit_decl 0x7ffff7ff81e0 D.24> RM
size <integer_cst 0x7ffff68ccca8 8>
chain <type_decl 0x7ffff6900b48 short_short_integer>>
arg 0 <eq_expr 0x7ffff6573938
...
arg 1 <compound_expr 0x7ffff65739b0 type <integer_type 0x7ffff6572dc8
short_short_integer>
side-effects
...
arg 2 <plus_expr 0x7ffff6573910 type <integer_type 0x7ffff6572dc8
short_short_integer>
...
that's unexpected to the code generated by genmatch and I don't see
how omit_one_operand would handle that either. The COND_EXPR is
originally built with TREE_SIDE_EFFECTS set but:
Hardware watchpoint 7: *$43
Old value = 65595
New value = 59
emit_check (gnu_cond=<eq_expr 0x7ffff6573938>,
gnu_expr=<plus_expr 0x7ffff6573910>, reason=10, gnat_node=2320)
at /space/rguenther/src/svn/trunk/gcc/ada/gcc-interface/trans.c:8823
8823 return gnu_result;
$45 = 0
so the Ada frontend resets the flag (improperly?):
emit_check (gnu_cond=<eq_expr 0x7ffff6573938>,
gnu_expr=<plus_expr 0x7ffff6573910>, reason=10, gnat_node=2320)
at /space/rguenther/src/svn/trunk/gcc/ada/gcc-interface/trans.c:8823
8823 return gnu_result;
$45 = 0
(gdb) l
8818
8819 /* GNU_RESULT has side effects if and only if GNU_EXPR has:
8820 we don't need to evaluate it just for the check. */
8821 TREE_SIDE_EFFECTS (gnu_result) = TREE_SIDE_EFFECTS (gnu_expr);
8822
8823 return gnu_result;
8824 }
Richard.
