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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. This fixes PR111369, where one of the bitint*.c tests FAILs with GCC_TEST_RUN_EXPENSIVE=1. 2023-10-04 Jakub Jelinek <jakub@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.
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