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Re: [tree-ssa] Grammar for GIMPLE condexprs
- From: Jason Merrill <jason at redhat dot com>
- To: Diego Novillo <dnovillo at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Tue, 25 Mar 2003 13:18:12 -0500
- Subject: Re: [tree-ssa] Grammar for GIMPLE condexprs
- References: <20030325153241.GA8095@tornado.toronto.redhat.com>
On Tue, 25 Mar 2003 10:32:41 -0500, Diego Novillo <dnovillo at redhat dot com> wrote:
> The GIMPLE grammar for conditional expressions says:
>
> -----------------------------------------------------------------------------
> relop
> : '<'
> | '<='
> | '>'
> | '>='
> | '=='
> | '!='
>
> condexpr
> : val
> | val relop val
>
> val
> : ID
> | CONST
> -----------------------------------------------------------------------------
>
> And yet, the gimplifier is emitting things like
>
> -----------------------------------------------------------------------------
> T.225 = a.224 < 0;
> b.226 = (int)b;
> T.227 = b.226 >= 0;
> if (T.225 ^ T.227)
is_simple_condexpr currently allows TRUTH_XOR_EXPR, which I assume is the
code in the above tree, rather than the C ^, which is BIT_XOR_EXPR. This
seems reasonable to me.
> It shouldn't be too hard to change that to
>
> if ((T.225 ^ T.227) != 0)
>
> Right? Do you see any problems if I make that change?
Why would you want to suppress just that comparison? I note that do_jump
doesn't have special handling for TRUTH_AND_EXPR or TRUTH_OR_EXPR, either.
> A pass that I'm working on needs to build TRUTH_NOT_EXPR <cond> and it's
> failing when I call fold() on the generated tree (because
> invert_truthvalue can't deal with VAR_DECLs).
It should. Perhaps we should try to give boolean gimple temps BOOLEAN_TYPE
even in C.
Jason