Thanks for doing this. Kyrill Tkachov <kyrylo.tkac...@foss.arm.com> writes: > diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c > index > 2e7aa5c12952ab1a9b49b5adaf23710327e577d3..af06d7502cebac03cefc689b2646874b8397e767 > 100644 > --- a/gcc/simplify-rtx.c > +++ b/gcc/simplify-rtx.c > @@ -6474,6 +6474,18 @@ simplify_subreg (machine_mode outermode, rtx op, > return NULL_RTX; > } > > + /* Simplify (subreg:QI (and:SI (reg:SI) (const_int 0xffff)) 0) > + into (subreg:QI (reg:SI) 0). */ > + scalar_int_mode int_outermode, int_innermode; > + if (!paradoxical_subreg_p (outermode, innermode) > + && is_a <scalar_int_mode> (outermode, &int_outermode) > + && is_a <scalar_int_mode> (innermode, &int_innermode) > + && GET_CODE (op) == AND && CONST_INT_P (XEXP (op, 1)) > + && known_eq (subreg_lowpart_offset (outermode, innermode), byte) > + && (~INTVAL (XEXP (op, 1)) & GET_MODE_MASK (int_outermode)) == 0 > + && validate_subreg (outermode, innermode, XEXP (op, 0), byte)) > + return gen_rtx_SUBREG (outermode, XEXP (op, 0), byte); > + > /* A SUBREG resulting from a zero extension may fold to zero if > it extracts higher bits that the ZERO_EXTEND's source bits. */ > if (GET_CODE (op) == ZERO_EXTEND && SCALAR_INT_MODE_P (innermode))
I think it'd be better to do this in simplify_truncation (shared by the subreg code and the TRUNCATE code). The return would then be simplify_gen_unary (TRUNCATE, ...), which will become a subreg if TRULY_NOOP_TRUNCATION. Thanks, A different Richard
