On Mon, 13 Jan 2020, Jakub Jelinek wrote:
> On Sat, Jan 11, 2020 at 05:30:52PM +0100, Jakub Jelinek wrote:
> > On Sat, Jan 11, 2020 at 05:24:19PM +0100, Andreas Schwab wrote:
> > > ../../gcc/tree-ssa-forwprop.c: In function 'bool
> > > simplify_count_trailing_zeroes(gimple_stmt_iterator*)':
> > > ../../gcc/tree-ssa-forwprop.c:1925:23: error: variable 'mode' set but not
> > > used [-Werror=unused-but-set-variable]
> > > 1925 | scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
> > > | ^~~~
> >
> > Oops, then I think we need following, but can't commit it until Monday.
>
> Unfortunately, at least when testing x86_64-linux to s390x-linux cross,
> there are two warnings instead of just one:
> ../../gcc/tree-ssa-forwprop.c: In function ‘bool
> simplify_count_trailing_zeroes(gimple_stmt_iterator*)’:
> ../../gcc/tree-ssa-forwprop.c:1925:23: warning: variable ‘mode’ set but not
> used [-Wunused-but-set-variable]
> scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
> ^~~~
> ../../gcc/tree-ssa-forwprop.c:1932:7: warning: ‘ctzval’ may be used
> uninitialized in this function [-Wmaybe-uninitialized]
> if (zero_val != ctzval && !(zero_val == 0 && ctzval == type_size))
> ^~
> at -O0 and just the first one at -O2.
> The first warning (or with error with -Werror) can be cured by the
> patch I've posted on Saturday, I've successfully bootstrapped/regtested
> it in the mean time on x86_64-linux and i686-linux, tested on aarch64-linux
> including the testcase and tested on s390x-linux.
>
> Or we could also initialize ctzval as in the following patch to e.g. match
> what we do in vr-values.c with *_DEFINED_VALUE_AT_ZERO. Except for the
> x86_64-linux/i686-linux bootstrap/regtest, tested similarly to the above.
>
> So, ok for trunk and which one?
OK, the one below looks good to me.
> 2020-01-13 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/90838
> * tree-ssa-forwprop.c (simplify_count_trailing_zeroes): Use
> SCALAR_INT_TYPE_MODE directly in CTZ_DEFINED_VALUE_AT_ZERO macro
> argument rather than to initialize temporary for targets that
> don't use the mode argument at all. Initialize ctzval to avoid
> warning at -O0.
>
> --- gcc/tree-ssa-forwprop.c
> +++ gcc/tree-ssa-forwprop.c
> @@ -1920,10 +1920,10 @@ simplify_count_trailing_zeroes (gimple_stmt_iterator
> *gsi)
> res_ops[1], res_ops[2], zero_val))
> {
> tree type = TREE_TYPE (res_ops[0]);
> - HOST_WIDE_INT ctzval;
> + HOST_WIDE_INT ctzval = 0;
> HOST_WIDE_INT type_size = tree_to_shwi (TYPE_SIZE (type));
> - scalar_int_mode mode = SCALAR_INT_TYPE_MODE (type);
> - bool zero_ok = CTZ_DEFINED_VALUE_AT_ZERO (mode, ctzval) == 2;
> + bool zero_ok
> + = CTZ_DEFINED_VALUE_AT_ZERO (SCALAR_INT_TYPE_MODE (type), ctzval) == 2;
>
> /* Skip if there is no value defined at zero, or if we can't easily
> return the correct value for zero. */
>
> Jakub
