On Mon, Nov 2, 2020 at 5:52 PM Chen Qun <[email protected]> wrote:
>
> The compiler cannot determine whether the return values of the
> xtensa_operand_is_register(isa, opc, opnd)
> and xtensa_operand_is_visible(isa, opc, opnd) functions are the same.
It doesn't have to because 1) they definitely are not the same, but
2) it doesn't matter.
> So,it assumes that 'rf' is not assigned, but it's used.
The assumption is wrong. rf is used under the 'if (register_file)'
condition and register_file is initialized to NULL and then set
to something non-NULL based on the value of rf here:
958 if (xtensa_operand_is_register(isa, opc, opnd)) {
959 rf = xtensa_operand_regfile(isa, opc, opnd);
960 register_file = dc->config->regfile[rf];
> The compiler showed warning:
> target/xtensa/translate.c: In function ‘disas_xtensa_insn’:
> target/xtensa/translate.c:985:43: warning: ‘rf’ may be used uninitialized in
> this function [-Wmaybe-uninitialized]
> 985 | arg[vopnd].num_bits =
> xtensa_regfile_num_bits(isa, rf);
> |
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Add a default value for 'rf' to prevented the warning.
I don't see it doing default build with gcc 8.3. But then I don't see
-Wmaybe-uninitialized in the compiler command line either.
> Reported-by: Euler Robot <[email protected]>
> Signed-off-by: Chen Qun <[email protected]>
> ---
> Cc: Max Filippov <[email protected]>
> ---
> target/xtensa/translate.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/xtensa/translate.c b/target/xtensa/translate.c
> index 944a157747..eea851bbe7 100644
> --- a/target/xtensa/translate.c
> +++ b/target/xtensa/translate.c
> @@ -953,7 +953,7 @@ static void disas_xtensa_insn(CPUXtensaState *env,
> DisasContext *dc)
>
> for (opnd = vopnd = 0; opnd < opnds; ++opnd) {
> void **register_file = NULL;
> - xtensa_regfile rf;
> + xtensa_regfile rf = -1;
Please use XTENSA_UNDEFINED instead if you still think this
is worth changing.
--
Thanks.
-- Max
