On Tue, 3 Oct 2023, Jakub Jelinek wrote:
> Hi!
>
> On Sat, Sep 30, 2023 at 11:57:38AM +0200, Jakub Jelinek wrote:
> > > This fixes PR111369, where one of the bitint*.c tests FAILs with
> > > GCC_TEST_RUN_EXPENSIVE=1.
> >
> > Though, I think there is an preexisting issue which the
> > build_nonstandard_integer_type didn't help with; if type is signed 1-bit
> > precision, then I think a ? ~t : t could be valid, but -(type)a would invoke
> > UB if a is 1 - the cast would make it -1 and negation of -1 in signed 1-bit
> > invokes UB.
> > So perhaps we should guard this optimization on type having element
> > precision > 1
> > or being unsigned. Plus the (convert:type @2) didn't make sense, @2 already
> > must have TREE_TYPE type.
>
> In the light of the PR111668 patch which shows that
> build_nonstandard_integer_type is needed (at least for some signed prec > 1
> BOOLEAN_TYPEs if we use e.g. negation), I've reworked this patch and handled
> the last problematic build_nonstandard_integer_type call in there as well.
>
> In the x == cstN ? cst4 : cst3 optimization it uses
> build_nonstandard_integer_type solely for BOOLEAN_TYPEs (I really don't see
> why ENUMERAL_TYPEs would be a problem, we treat them in GIMPLE as uselessly
> convertible to same precision/sign INTEGER_TYPEs), for INTEGER_TYPEs it is
> really a no-op (might return a different type, but always INTEGER_TYPE
> with same TYPE_PRECISION same TYPE_UNSIGNED) and for BITINT_TYPE with larger
> precisions really harmful (we shouldn't create large precision
> INTEGER_TYPEs).
>
> The a?~t:t optimization just omits the negation of a in type for 1-bit
> precision types or any BOOLEAN_TYPEs. I think that is correct, because
> for both signed and unsigned 1-bit precision type, cast to type of a bool
> value yields already 0, -1 or 0, 1 values and for 1-bit precision negation
> of that is still 0, -1 or 0, 1 (except for invoking sometimes UB).
> And for signed larger precision BOOLEAN_TYPEs I think it is correct as well,
> cast of [0, 1] to type yields 0, -1 and those can be xored with 0 or -1
> to yield the proper result, any other values would be UB.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
> 2023-10-03 Jakub Jelinek <ja...@redhat.com>
>
> PR middle-end/111369
> * match.pd (x == cstN ? cst4 : cst3): Use
> build_nonstandard_integer_type only if type1 is BOOLEAN_TYPE.
> Fix comment typo. Formatting fix.
> (a?~t:t -> (-(a))^t): Always convert to type rather
> than using build_nonstandard_integer_type. Perform negation
> only if type has precision > 1 and is not signed BOOLEAN_TYPE.
>
> --- gcc/match.pd.jj 2023-10-03 10:33:30.817614648 +0200
> +++ gcc/match.pd 2023-10-03 11:29:54.089566764 +0200
> @@ -5178,7 +5178,7 @@ (define_operator_list SYNC_FETCH_AND_AND
>
> /* Optimize
> # x_5 in range [cst1, cst2] where cst2 = cst1 + 1
> - x_5 ? cstN ? cst4 : cst3
> + x_5 == cstN ? cst4 : cst3
> # op is == or != and N is 1 or 2
> to r_6 = x_5 + (min (cst3, cst4) - cst1) or
> r_6 = (min (cst3, cst4) + cst1) - x_5 depending on op, N and which
> @@ -5214,7 +5214,8 @@ (define_operator_list SYNC_FETCH_AND_AND
> type1 = type;
> auto prec = TYPE_PRECISION (type1);
> auto unsign = TYPE_UNSIGNED (type1);
> - type1 = build_nonstandard_integer_type (prec, unsign);
> + if (TREE_CODE (type1) == BOOLEAN_TYPE)
> + type1 = build_nonstandard_integer_type (prec, unsign);
> min = wide_int::from (min, prec,
> TYPE_SIGN (TREE_TYPE (@0)));
> wide_int a = wide_int::from (wi::to_wide (arg0), prec,
> @@ -5253,14 +5254,7 @@ (define_operator_list SYNC_FETCH_AND_AND
> }
> (if (code == PLUS_EXPR)
> (convert (plus (convert:type1 @0) { arg; }))
> - (convert (minus { arg; } (convert:type1 @0)))
> - )
> - )
> - )
> - )
> - )
> - )
> -)
> + (convert (minus { arg; } (convert:type1 @0))))))))))
> #endif
>
> (simplify
> @@ -6758,13 +6752,11 @@ (define_operator_list SYNC_FETCH_AND_AND
> (with { bool wascmp; }
> (if (INTEGRAL_TYPE_P (type)
> && bitwise_inverted_equal_p (@1, @2, wascmp)
> - && (!wascmp || element_precision (type) == 1))
> - (with {
> - auto prec = TYPE_PRECISION (type);
> - auto unsign = TYPE_UNSIGNED (type);
> - tree inttype = build_nonstandard_integer_type (prec, unsign);
> - }
> - (convert (bit_xor (negate (convert:inttype @0)) (convert:inttype
> @2)))))))
> + && (!wascmp || TYPE_PRECISION (type) == 1))
> + (if ((!TYPE_UNSIGNED (type) && TREE_CODE (type) == BOOLEAN_TYPE)
> + || TYPE_PRECISION (type) == 1)
> + (bit_xor (convert:type @0) @2)
> + (bit_xor (negate (convert:type @0)) @2)))))
> #endif
>
> /* Simplify pointer equality compares using PTA. */
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)
