Please excuse a comment from the gallery:
On Mon, 28 Sep 2020, will schmidt via Gcc-patches wrote:
> On Fri, 2020-09-04 at 12:52 -0300, Raoni Fassina Firmino via Gcc-patches
> wrote:
> > 2020-08-13 Raoni Fassina Firmino <ra...@linux.ibm.com>
> >
> > gcc/ChangeLog:
> > * config/rs6000/rs6000.md (fegetroundsi): New pattern.
> > (feclearexceptsi): New Pattern.
> > (feraiseexceptsi): New Pattern.
> > +(define_expand "feraiseexceptsi"
> > + [(use (match_operand:SI 1 "const_int_operand" "n"))
> > + (set (match_operand:SI 0 "gpc_reg_operand")
> > + (const_int 0))]
> > + "TARGET_HARD_FLOAT"
> > +{
> > + switch (INTVAL (operands[1]))
> > + {
> > + case 0x2000000: /* FE_INEXACT */
> > + case 0x4000000: /* FE_DIVBYZERO */
> > + case 0x8000000: /* FE_UNDERFLOW */
> > + case 0x10000000: /* FE_OVERFLOW */
> > + break;
> > + default:
> > + FAIL;
> > + }
> > +
> > + rtx tmp = gen_rtx_CONST_INT (SImode, __builtin_clz (INTVAL
> > (operands[1])));
This doesn't appear to be very portable, to any-cxx11-compiler
that doesn't pretend to be gcc-intrinsics-compatible.
If the valid values had been more complicated, there'd be
bitmap.c:bitmap_last_set_bit to follow for a suitable portable
pattern. It conditionalizes like:
#if GCC_VERSION >= 3004
gcc_assert (sizeof (long) == sizeof (word));
bit_no += BITMAP_WORD_BITS - __builtin_clzl (word) - 1;
#else
...
#endif
Better, there's "ffs".
brgds, H-P
PS. No less than four targets fail like that. Meh.
