On Fri, 13 Nov 2015, Michael Meissner wrote:
> This patch should address the following IEEE problems with the libgcc emulator
> with exceptions, etc. Steve is working on patches to libdfp for Decimal
> conversions.
Are the libgcc2.c functions for KFmode and the corresponding complex mode
KCmode (__divkc3 __mulkc3 __powikf2) also planned for GCC 6?
> * config/rs6000/sfp-machine.h (_FP_W_TYPE_SIZE): Update
> defintiions to use 64-bit types for 64-bit systems or 32-bit VSX
> systems with IEEE 128-bit floating point support.
> (_FP_W_TYPE): Likewise.
> (_FP_WS_TYPE): Likewise.
> (_FP_I_TYPE): Likewise.
> (TItype): Add defintions for IEEE 128-bit floating point support.
> (UTItype): Likewise.
> (TI_BITS): Likewise.
> (_FP_MUL_MEAT_Q): Use 64-bit types on 64-bit systems and for
> 32-bit VSX systems with IEEE 128-bit floating point.
> (_FP_DIV_MEAT_Q): Likewise.
> (_FP_NANFRAC_Q): Likewise.
This ChangeLog entry doesn't seem to have been updated for the exceptions
/ rounding modes support.
> +#define ISA_BIT(x) (1 << (63 - x))
I think all the new sfp-machine.h code for integration with hardware
exceptions and rounding modes needs to be conditional on hard-float +
FPRs, so it doesn't affect building for SFmode / DFmode for soft-float /
e500.
> + /* First do the unordered comparison. */
> + FP_CMP_UNORD_Q (r, A, B, 1);
> + if (r)
> + r2 = PPC_UNORDERED;
> +
> + else
> + {
> + /* If the value is not unordered, do the normal comparison. */
> + FP_CMP_Q (r, A, B, 2, 2);
> + if (r == CMP_INVALID)
> + FP_SET_EXCEPTION (FP_EX_INVALID);
> +
> + r2 = ((r < CMP_LOW || r > CMP_HIGH)
> + ? PPC_UNORDERED
> + : ppc_cr_map[r-CMP_LOW]);
This may be correct, but it's overly complicated. All the handling in the
"else" case for exceptions / unordered is dead code, since in that case
you know that the values aren't unordered. And you can more simply do
FP_CMP_Q (r, A, B, 2, 1);
at which point "invalid" has been raised if appropriate (for signaling
NaNs but not for other arguments), and r contains one of the values -1, 0,
1, 2, which you can map directly to the appropriate return value.
--
Joseph S. Myers
[email protected]
