On Wed, 2020-02-05 at 20:47 +0100, Henri Cloetens wrote:
> Hello all,
>
> I have a problem with zero extension from BI mode into SI mode.
> I try to compile following piece of code:
>
> _Bool check_test(int a, int b)
> {
> _Bool check = (a > b) ;
> return(check) ;
> }
>
> The description is such that it puts the _Bool check flag in the
> Condition Code register.
> This is a 16-bit register file in the machine that handles booleans.
> The calling convention of the machine returns the return value in
> register 32.
> To do this operation, a sign extend from the boolean (BI) check to the
> int (SI)
> R20 needs to be done. When I run the code through the compiler, after
> the expand step,
> I get following:
>
> file : check_test2.c.233r.expand
>
> <preceding INSNs putting the result into check>
>
> (insn 10 9 11 2 (set (reg:QI 79 [ check ])
> (reg:BI 81)) "check_test2.c":3:7 -1
> (nil))
> (insn 11 10 12 2 (set (reg:SI 82)
> (zero_extend:SI (reg:QI 79 [ check ]))) "check_test2.c":4:7 -1
> (nil))
> (insn 12 11 16 2 (set (reg/v:SI 74 [ <retval> ])
> (reg:SI 82)) "check_test2.c":4:7 -1
> (nil))
>
> The first insn of this list is not consistent. I mean, as far as I
> understand it, it should be a zero_extend and not a set.
Right. You can't mix modes like that.
The way I'd debug this would be to put a conditional breakpoint in
make_insn_raw using cur_insn_uid == 10 as the condition (cur_insn_uid
is a macro these days, so you'll have to expand it to get the field
within the crtl structure you want).
jeff
