[Mesa-dev] [PATCH 2/7] glsl: Avoid aliasing violations.

[Brian Paul]

On 06/27/2016 03:42 PM, Matt Turner wrote:
> ---
>   src/compiler/glsl/ir_constant_expression.cpp    | 11 +++--------
>   src/compiler/glsl/link_uniform_initializers.cpp |  3 +--
>   2 files changed, 4 insertions(+), 10 deletions(-)
>
> diff --git a/src/compiler/glsl/ir_constant_expression.cpp b/src/compiler/glsl/ir_constant_expression.cpp
> index e79d5ef..7c6a17d 100644
> --- a/src/compiler/glsl/ir_constant_expression.cpp
> +++ b/src/compiler/glsl/ir_constant_expression.cpp
> @@ -1573,18 +1573,13 @@ ir_expression::constant_expression_value(struct hash_table *variable_context)
>            data.f[c] = CLAMP(op[0]->value.f[c], 0.0f, 1.0f);
>         }
>         break;
> -   case ir_unop_pack_double_2x32: {
> +   case ir_unop_pack_double_2x32:
>         /* XXX needs to be checked on big-endian */
> -      uint64_t temp;
> -      temp = (uint64_t)op[0]->value.u[0] | ((uint64_t)op[0]->value.u[1] << 32);
> -      data.d[0] = *(double *)&temp;
> -
> +      memcpy(&data.d[0], &op[0]->value.u[0], sizeof(double));
>         break;
> -   }
>      case ir_unop_unpack_double_2x32:
>         /* XXX needs to be checked on big-endian */
> -      data.u[0] = *(uint32_t *)&op[0]->value.d[0];
> -      data.u[1] = *((uint32_t *)&op[0]->value.d[0] + 1);
> +      memcpy(&data.u[0], &op[0]->value.d[0], sizeof(double));
>         break;
>
>      case ir_triop_bitfield_extract: {
> diff --git a/src/compiler/glsl/link_uniform_initializers.cpp b/src/compiler/glsl/link_uniform_initializers.cpp
> index acf8222..98a2397 100644
> --- a/src/compiler/glsl/link_uniform_initializers.cpp
> +++ b/src/compiler/glsl/link_uniform_initializers.cpp
> @@ -65,8 +65,7 @@ copy_constant_to_storage(union gl_constant_value *storage,
>   	 break;
>         case GLSL_TYPE_DOUBLE:
>            /* XXX need to check on big-endian */
> -         storage[i * 2].u = *(uint32_t *)&val->value.d[i];
> -         storage[i * 2 + 1].u = *(((uint32_t *)&val->value.d[i]) + 1);
> +         memcpy(&storage[i * 2].u, &val->value.d[i], sizeof(double));
>            break;
>         case GLSL_TYPE_BOOL:
>   	 storage[i].b = val->value.b[i] ? boolean_true : 0;
>

For 2-7, Reviewed-by: Brian Paul <brianp at vmware.com>

Though, in patch 6, as long as you're there, I wonder if we should use 
parenthesized (offset) in the macro bodies, just to be safe.

-Brian