Ian Romanick <i...@freedesktop.org> writes: > From: Ian Romanick <ian.d.roman...@intel.com> > > Three parts to the fix: > > 1. If the array dereference is a constant index, figure out the real > write mask. > > 2. If the array dereference not is a constant index, assume the > assignment may generate any component. > > 3. If the array dereference not is a constant index, assume the > assigment will not kill any previous component write.
Man I wish we didn't leave vector array derefs in the GLSL IR. Or
rather, I wish we didn't try optimizing on this IR.
> -static bool debug = false;
> +static bool debug = true;
left the debug on.
>
> namespace {
>
> +static bool
> +is_array_deref_of_vector(ir_rvalue *ir)
> +{
> + if (ir->ir_type == ir_type_dereference_array) {
> + ir_dereference_array *const d = ir->as_dereference_array();
> +
> + assert(d != NULL);
Or just make the if statement "if (d)" and drop the assert.
> + * a vector, the \c write_mask of the assignment is returned. If the LHS of
> + * the assignment is an array dereference, the write mask is a lie. The
> + * actual write mask is determined by the array index. If the array index is
> + * a constant, calculate the mask from that constant.
> + * If the index is not a constant, the function can operation in one of two
operate
> + * modes. In the first mode, when \c want_availability_mask is \c true, it
> is
> + * assumed that any field of the vector may be written. This is used when
> + * adding an assignment to the assignment list. In the second mode, when
> + * \c want_availability_mask is \c false, it is assumed that no fields of the
> + * vector are written. This is used when trying to remove earlier
> assignments
> + * from the list.
> + */
> +static int
> +may_set_mask(ir_assignment *ir, bool want_availability_mask)
> +{
> + int mask = ir->write_mask;
> +
> + /* If the LHS is an array derefernce of a vector, try to figure out what
> + * the real write mask is. If the index is not a constant, assume that
> any
> + * element may be written.
> + */
> + if (is_array_deref_of_vector(ir->lhs)) {
> + ir_dereference_array *const d = ir->lhs->as_dereference_array();
> + ir_constant *const c = d->array_index->as_constant();
> +
> + if (c != NULL) {
> + const int idx = (c != NULL) ? c->get_uint_component(0) : -1;
> +
> + if (idx >= 0 && idx <= 3)
> + mask = 1U << idx;
> + else
> + mask = 0;
> + } else {
> + /* Set the write-mask depending on the size of the vector.
> + */
> + if (want_availability_mask)
> + mask = (1U << d->array->type->vector_components()) - 1;
> + else
> + mask = 0;
> + }
> + }
> +
> + return mask;
> +}
> +
> class assignment_entry : public exec_node
> {
> public:
> @@ -51,7 +114,7 @@ public:
> assert(ir);
> this->lhs = lhs;
> this->ir = ir;
> - this->available = ir->write_mask;
> + this->available = may_set_mask(ir, true);
I don't think the want_availability_mask makes sense. If you're noting
an array deref of a vector for later dead code elimination, a later
instruction that sets the vector's .x shouldn't go turn off .x of this
instruction.
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