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?
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
