All stream output objects need to have a stream index allocated,
whether they are used or not.
We allocate stream outputs here, before other objects are allocated,
because the stream index is needed to create the appropriate output
semantic variables during append_output_copy(), which will be called
in a lowering pass for the Append() method.
Currently program errors might result on instructions that use
ctx->error_instr as src. In case we hit YYABORT while parsing another
part of the HLSL source, we have to make sure that the block that
contains the instruction is properly cleaned up, or we might hit the
vkd3d:590273:err:hlsl_free_instr Failed assertion: list_empty(&node->uses)
assertion when hlsl_ctx_cleanup() is called after the YYABORT.
Consider the following shader:
float4 main() : sv_target
{
// Statement A
int p = foo; // initializer argument is ERROR.
// Statement B
undeclared_fun(); // triggers YYABORT.
}
Statement A will src the ctx->error_instr because of the undeclared
identifier and Statement B will trigger an YYABORT because of the
undeclared function.
