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?
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
