Thanks Richard for comments. > Why is it important to constrain the widen-mult input to a > fixed precision at all?
I suppose widen-mult only occurs when the result exceed the max bits of gpr. So, here I would like to make sure the precision is matching the bits of gpr. For rv32 with 32-bits gpr, 32 bits * 32 bits => 64 bits 15 │ _1 = (long long unsigned int) a_4(D); 16 │ _2 = (long long unsigned int) b_5(D); 17 │ _9 = (unsigned int) _1; 18 │ _10 = (unsigned int) _2; 19 │ x_6 = _9 w* _10; For rv64 with 64-bits gpr, 64 bits * 64 bits => 128 bits 15 │ _1 = (__int128 unsigned) a_4(D); 16 │ _2 = (__int128 unsigned) b_5(D); 17 │ _9 = (unsigned long) _1; 18 │ _10 = (unsigned long) _2; 19 │ x_6 = _9 w* _10; But if it is a widen-mul, it looks like that the ops of widen-mul should be the max bits of gpr already. Or it will be a normal mul, then looks we don't need to check that anymore, am I understanding correct? Pan -----Original Message----- From: Richard Biener <richard.guent...@gmail.com> Sent: Friday, July 11, 2025 2:23 PM To: Li, Pan2 <pan2...@intel.com> Cc: gcc-patches@gcc.gnu.org; juzhe.zh...@rivai.ai; kito.ch...@gmail.com; jeffreya...@gmail.com; rdapp....@gmail.com; Chen, Ken <ken.c...@intel.com>; Liu, Hongtao <hongtao....@intel.com> Subject: Re: [PATCH v1 1/2] Match: Leverage BITS_PER_WORD for unsigned SAT_MUL pattern On Fri, Jul 11, 2025 at 6:51 AM <pan2...@intel.com> wrote: > > From: Pan Li <pan2...@intel.com> > > The widen mul has different source type for differnt platform, > like rv32 or rv64. For rv32, the source of widen mul is 32-bits > while 64-bits in rv64. Thus, leverage HOST_WIDE_INT is not that > correct and result in the pattern match failures in 32-bits system > like rv32. > > Thus, leverage the BITS_PER_WORD instead for this pattern. > > gcc/ChangeLog: > > * match.pd: Leverage BITS_PER_WORD instead of HOST_WIDE_INT > for widen mul precision check. > > Signed-off-by: Pan Li <pan2...@intel.com> > --- > gcc/match.pd | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/gcc/match.pd b/gcc/match.pd > index 67b33eee5f7..7f31705b652 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -3605,11 +3605,10 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > unsigned widen_prec = TYPE_PRECISION (TREE_TYPE (@3)); > unsigned cvt5_prec = TYPE_PRECISION (TREE_TYPE (@5)); > unsigned cvt6_prec = TYPE_PRECISION (TREE_TYPE (@6)); > - unsigned hw_int_prec = sizeof (HOST_WIDE_INT) * 8; > wide_int c2 = wi::to_wide (@2); > wide_int max = wi::mask (prec, false, widen_prec); > bool c2_is_max_p = wi::eq_p (c2, max); > - bool widen_mult_p = cvt5_prec == cvt6_prec && hw_int_prec == cvt5_prec; > + bool widen_mult_p = cvt5_prec == cvt6_prec && BITS_PER_WORD == > cvt5_prec; Why is it important to constrain the widen-mult input to a fixed precision at all? > } > (if (widen_prec > prec && c2_is_max_p && widen_mult_p))))) > ) > -- > 2.43.0 >
