Tamar Christina <tamar.christ...@arm.com> writes:
> @@ -4613,6 +4615,66 @@ aarch64_legitimize_address_displacement (rtx *disp,
> rtx *off, machine_mode mode)
> return true;
> }
>
> +/* Return the binary representation of floating point constant VALUE in
> INTVAL.
> + If the value cannot be converted, return false without setting INTVAL.
> + The conversion is done in the given MODE. */
> +bool
> +aarch64_reinterpret_float_as_int (rtx value, unsigned HOST_WIDE_INT *intval)
> +{
> + machine_mode mode = GET_MODE (value);
> + if (GET_CODE (value) != CONST_DOUBLE
> + || !SCALAR_FLOAT_MODE_P (mode)
> + || GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT)
> + return false;
> +
> + unsigned HOST_WIDE_INT ival = 0;
> +
> + /* Only support up to DF mode. */
> + gcc_assert (GET_MODE_BITSIZE (mode) <= 64);
> + int needed = GET_MODE_BITSIZE (mode) == 64 ? 2 : 1;
> +
> + long res[2];
> + real_to_target (res,
> + CONST_DOUBLE_REAL_VALUE (value),
> + REAL_MODE_FORMAT (mode));
> +
> + ival = zext_hwi (res[needed - 1], 32);
> + for (int i = needed - 2; i >= 0; i--)
> + {
> + ival <<= 32;
> + ival |= zext_hwi (res[i], 32);
> + }
> +
> + *intval = ival;
> + return true;
> +}
> +
> +/* Return TRUE if rtx X is an immediate constant that can be moved in
> + created using a single MOV(+MOVK) followed by an FMOV. */
Typo.
> +bool
> +aarch64_float_const_rtx_p (rtx x)
> +{
> + machine_mode mode = GET_MODE (x);
> + if (mode == VOIDmode)
> + return false;
> +
> + /* Determine whether it's cheaper to write float constants as
> + mov/movk pairs over ldr/adrp pairs. */
> + unsigned HOST_WIDE_INT ival;
> +
> + if (GET_CODE (x) == CONST_DOUBLE
> + && SCALAR_FLOAT_MODE_P (mode)
> + && aarch64_reinterpret_float_as_int (x, &ival))
> + {
> + machine_mode imode = mode == HFmode ? SImode : int_mode_for_mode
> (mode);
> + int num_instr = aarch64_internal_mov_immediate
> + (NULL_RTX, GEN_INT (ival), false, imode);
Sorry to be a broken record on this, but since you explicitly zero-extend
the real_to_target results from 32 bits, this will lead to an invalid
32-bit constant when the top bit of an SImode value is set,
e.g. (const_int 0x8000_0000) instead of (const_int 0xffff_ffff_8000_0000).
Using gen_int_mode would avoid this. In general it's better to use
gen_int_mode instead of GEN_INT whenever the mode is known, to avoid
this kind of corner case.
There's another instance later in the patch.
Thanks,
Richard
