[PATCH 4/5] d3dcompiler: Don't use assignment instructions as sources.

[Matteo Bruni]

On Tue, Jun 30, 2020 at 2:03 AM Zebediah Figura <z.figura12 at gmail.com> wrote:
>
> Signed-off-by: Zebediah Figura <zfigura at codeweavers.com>
> ---
>  dlls/d3dcompiler_43/d3dcompiler_private.h |  2 ++
>  dlls/d3dcompiler_43/utils.c               | 14 ++++++++++++--
>  2 files changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/dlls/d3dcompiler_43/d3dcompiler_private.h b/dlls/d3dcompiler_43/d3dcompiler_private.h
> index 23eff210940..2ff019d45a6 100644
> --- a/dlls/d3dcompiler_43/d3dcompiler_private.h
> +++ b/dlls/d3dcompiler_43/d3dcompiler_private.h
> @@ -786,6 +786,8 @@ enum hlsl_ir_expr_op {
>      HLSL_IR_UNOP_POSTINC,
>      HLSL_IR_UNOP_POSTDEC,
>
> +    HLSL_IR_UNOP_IDENT,
> +
>      HLSL_IR_BINOP_ADD,
>      HLSL_IR_BINOP_SUB,
>      HLSL_IR_BINOP_MUL,
> diff --git a/dlls/d3dcompiler_43/utils.c b/dlls/d3dcompiler_43/utils.c
> index 4bc3b9b0a64..b5422abd1e8 100644
> --- a/dlls/d3dcompiler_43/utils.c
> +++ b/dlls/d3dcompiler_43/utils.c
> @@ -1448,6 +1448,7 @@ struct hlsl_ir_node *add_assignment(struct list *instrs, struct hlsl_ir_node *lh
>  {
>      struct hlsl_ir_assignment *assign = d3dcompiler_alloc(sizeof(*assign));
>      struct hlsl_type *lhs_type;
> +    struct hlsl_ir_node *copy;
>      DWORD writemask = 0;
>
>      lhs_type = lhs->data_type;
> @@ -1511,7 +1512,7 @@ struct hlsl_ir_node *add_assignment(struct list *instrs, struct hlsl_ir_node *lh
>          lhs = lhs_inner;
>      }
>
> -    init_node(&assign->node, HLSL_IR_ASSIGNMENT, lhs_type, lhs->loc);
> +    init_node(&assign->node, HLSL_IR_ASSIGNMENT, NULL, lhs->loc);
>      assign->writemask = writemask;
>      assign->lhs.var = load_from_node(lhs)->src.var;
>      hlsl_src_from_node(&assign->lhs.offset, load_from_node(lhs)->src.offset.node);
> @@ -1528,7 +1529,14 @@ struct hlsl_ir_node *add_assignment(struct list *instrs, struct hlsl_ir_node *lh
>      hlsl_src_from_node(&assign->rhs, rhs);
>      list_add_tail(instrs, &assign->node.entry);
>
> -    return &assign->node;
> +    /* Don't use the instruction itself as a source, as this makes structure
> +     * splitting easier. Instead copy it here. Since we retrieve sources from
> +     * the last instruction in the list, we do need to copy. */

Not just that, what we now define as an assignment (really a STORE)
doesn't really make sense anymore as a source.

The need to copy the instruction is a bit annoying though. What about
storing the result into a temporary variable and adding an extra load
instead? Does it make struct splitting hard / impossible (e.g. along
the lines of: replace this instruction with this other instruction and
the copy -> now we need to replace the copy -> back to square one)?

If the temporary var + extra load solution doesn't fly, I guess this
could be the rare case where the unary + comes in handy, instead of
making up a new operator.