[Mesa-dev] [PATCH 2/4] compiler: avoid 'unused variable' and 'may be used uninitialized' warnings

[Eric Engestrom]

On Tuesday, 2018-09-11 15:42:05 +0300, asimiklit.work at gmail.com wrote:
> From: Andrii Simiklit <andrii.simiklit at globallogic.com>
> 
> 1. nir/nir_lower_vars_to_ssa.c:691:21: warning:
>        unused variable ‘var’
>        nir_variable *var = path->path[0]->var;
> 
> 2. nir_types.cpp:558:31: warning:
>     ‘elem_align’ may be used uninitialized in this function
>            unsigned elem_size, elem_align;
>    nir_types.cpp:558:20: warning:
>    ‘elem_size’ may be used uninitialized in this function
>            unsigned elem_size, elem_align;
> 
> Signed-off-by: Andrii Simiklit <andrii.simiklit at globallogic.com>
> ---
>  src/compiler/nir/nir_lower_vars_to_ssa.c | 2 +-
>  src/compiler/nir_types.cpp               | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/compiler/nir/nir_lower_vars_to_ssa.c b/src/compiler/nir/nir_lower_vars_to_ssa.c
> index cd679be..96de261 100644
> --- a/src/compiler/nir/nir_lower_vars_to_ssa.c
> +++ b/src/compiler/nir/nir_lower_vars_to_ssa.c
> @@ -688,7 +688,7 @@ nir_lower_vars_to_ssa_impl(nir_function_impl *impl)
>        nir_deref_path *path = &node->path;
>  
>        assert(path->path[0]->deref_type == nir_deref_type_var);
> -      nir_variable *var = path->path[0]->var;
> +      MAYBE_UNUSED nir_variable *var = path->path[0]->var;
>  
>        /* We don't build deref nodes for non-local variables */
>        assert(var->data.mode == nir_var_local);

Sure, or you could simply remove the single-use extra local variable and
just fold it into the assert :)

> diff --git a/src/compiler/nir_types.cpp b/src/compiler/nir_types.cpp
> index d24f094..d39d87b 100644
> --- a/src/compiler/nir_types.cpp
> +++ b/src/compiler/nir_types.cpp
> @@ -542,7 +542,7 @@ glsl_get_natural_size_align_bytes(const struct glsl_type *type,
>     }
>  
>     case GLSL_TYPE_ARRAY: {
> -      unsigned elem_size, elem_align;
> +      unsigned elem_size = 0, elem_align = 0;

Not really keen on these ones; it looks like your compiler is ignoring the
unreachable() in glsl_get_natural_size_align_bytes() and mis-computing the
possible code-paths, resulting in it wrongly printing a warning.

I'd prefer to keep these two hunks as is, so that real issue in
glsl_get_natural_size_align_bytes() would get flagged appropriately.

>        glsl_get_natural_size_align_bytes(type->fields.array,
>                                          &elem_size, &elem_align);
>        *align = elem_align;
> @@ -554,7 +554,7 @@ glsl_get_natural_size_align_bytes(const struct glsl_type *type,
>        *size = 0;
>        *align = 0;
>        for (unsigned i = 0; i < type->length; i++) {
> -         unsigned elem_size, elem_align;
> +         unsigned elem_size = 0, elem_align = 0;
>           glsl_get_natural_size_align_bytes(type->fields.structure[i].type,
>                                             &elem_size, &elem_align);
>           *align = MAX2(*align, elem_align);
> -- 
> 2.7.4
> 
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev