On Fri, Sep 6, 2019 at 5:45 PM Ilya Leoshkevich <i...@linux.ibm.com> wrote:
>
> > Am 06.09.2019 um 13:07 schrieb Richard Biener <richard.guent...@gmail.com>:
> >
> > On Thu, Sep 5, 2019 at 1:10 PM Ilya Leoshkevich <i...@linux.ibm.com> wrote:
> >>
> >> Right now gimplifier does not allow VEC_COND_EXPR's condition to trap
> >> and introduces a temporary if this could happen, for example, generating
> >>
> >> _5 = _4 > { 2.0e+0, 2.0e+0, 2.0e+0, 2.0e+0 };
> >> _6 = VEC_COND_EXPR <_5, { -1, -1, -1, -1 }, { 0, 0, 0, 0 }>;
> >>
> >> from GENERIC
> >>
> >> VEC_COND_EXPR < (*b > { 2.0e+0, 2.0e+0, 2.0e+0, 2.0e+0 }) ,
> >> { -1, -1, -1, -1 } ,
> >> { 0, 0, 0, 0 } >
> >>
> >> This is not necessary and makes the resulting GIMPLE harder to analyze.
> >> In particular, one of the next patches in series needs to get to
> >> VEC_COND_EXPR's comparison code, which is not possible when a temporary
> >> is introduced.
> >>
> >> This patch takes special care to avoid introducing trapping comparisons
> >> in GIMPLE_COND. They are not allowed, because they would require 3
> >> outgoing edges (then, else and EH), which is awkward to say the least.
> >> Therefore, computations of such conditions should live in their own basic
> >> blocks.
> >
> > Comments inline (thanks for the work btw)
> >
> >> #endif /* GCC_GIMPLE_EXPR_H */
> >> diff --git a/gcc/gimple.c b/gcc/gimple.c
> >> index 633ef512a19..fd14fbec15e 100644
> >> --- a/gcc/gimple.c
> >> +++ b/gcc/gimple.c
> >> @@ -2144,6 +2144,8 @@ gimple_could_trap_p_1 (gimple *s, bool include_mem,
> >> bool include_stores)
> >> op = gimple_assign_rhs_code (s);
> >> if (get_gimple_rhs_class (op) == GIMPLE_BINARY_RHS)
> >> div = gimple_assign_rhs2 (s);
> >> + else if (op == COND_EXPR || op == VEC_COND_EXPR)
> >> + op = TREE_CODE (gimple_assign_rhs1 (s));
> >
> > I think this is not correct since we can have
> >
> > int i = fp > 1. ? intval1 : intval2
> >
> > and thus FLOAT_TYPE_P (t) is wrong. You need to do
> >
> > t = TREE_TYPE (op);
> >
> > as well I think.
>
> Doesn't this mean there is a problem with the existing logic too? If `s`
> is
>
> int i = fp > 1.;
>
> then
>
> t = gimple_expr_type (s);
>
> would give us BOOLEAN_TYPE instead of REAL_TYPE.
Yeah, that looks broken as well.
>
> Also, the new logic will probably be a bit more complicated, since I
> will first have to do:
>
> tree cond = gimple_assign_rhs1 (s);
>
> then see if `cond` is not e.g. an SSA_NAME, but rather a tcc_comparison,
> and only then
>
> t = TREE_TYPE (TREE_OPERAND (cond, 0))
>
> So I'd rather send a new version before merging this :-)
Fine with me ;)
Richard.
