Problem with zero extend from BI to SI

[Henri Cloetens <henri.cloetens@xxxxxxxxxx>]

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.
The use of the set creates all kinds of problems, because there are part 
of the infrastructure that do not allow a
set from BI to QI mode.
Is this a bug or what ?. I mean, I have seen code in cfexpand.c that 
derives the operand to use from the size of the
type, counted in bytes, and I guess both BI and QI are one byte, so does 
it then "forget" the expand ?.

Best Regards,

Henri.