Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=56162
Storing to a vector component using a non-constant index is not allowed
on profiles lower than 6.0. Unless this happens inside a loop that can be
unrolled, which we are not doing yet.
For this reason, a validate_nonconstant_vector_store_derefs pass is
added to detect these cases.
Ideally we would want to emit an hlsl_error on this pass, but before
implementing loop unrolling, we could reach this point on valid HLSL.
Also, as pointed out by Nikolay in the mentioned bug, currently
new_offset_from_path_index() fails an assertion when this happens,
because it expects an hlsl_ir_constant, so a check is added.
It also felt correct to emit an hlsl_fixme there, despite the
redundancy.
This preempts us from replacing a swizzle incorrectly, as in the
following example:
1: A.x = 1.0
2: A
3: A.x = 2.0
4: @2.x
were @4 ends up being 2.0 instead of 1.0, because that's the value stored in
A.x at time 4, and we should be querying it at time 2.
This also helps us to avoid replacing a swizzle with itself in copy-prop
which can result in infinite loops, as with the included tests this commit.
Consider the following sequence of instructions:
1 : A
2 : B = @1
3 : B
4 : A = @3
5 : @1.x
Current copy-prop would replace 5 so it points to @3 now:
1 : A
2 : B = @1
3 : B
4 : A = @3
5 : @3.x
But in the next iteration it would make it point back to @1, keeping it
spinning infinitively.
The solution is to index the instructions and don't replace the swizzle
if the new load happens after the current load.
Instead of only storing the value that each variable's component has at
the moment of the instruction currently handled by copy-prop, we store
the trace of all the historic values with their timestamps, i.e. the
instruction index on which the value was stored.
This would allow us to query the value that the variable had at the time
of execution of previous instructions.
The choice to store them in an rbtree was made early on. It does not seem likely
that HLSL programs would define many overloads for any of their functions, but I
suspect the idea was rather that intrinsics would be defined as plain
hlsl_ir_function_decl structures [cf. 447463e5900ca6a636998a65429b8a08a5441657]
and that some intrinsics that could operate on any type would therefore need
many overrides.
This is not how we deal with intrinsics, however. When the first intrinsics were
implemented I made the choice disregard this intended design, and instead match
and convert their types manually, in C. Nothing that has happened in the time
since has led me to question that choice, and in fact, the flexibility with
which we must accommodate functions has led me to believe that matching in this
way was definitely the right choice. The main other designs I see would have
been:
* define each intrinsic variant separately using existing HLSL types. Besides
efficiency concerns (i.e. this would take more space in memory, and would take
longer to generate each variant), the normal type-matching rules don't really
apply to intrinsics.
[For example: elementwise intrinsics like abs() return the same type as the
input, including preserving the distinction between float and float1. It is
legal to define separate HLSL overloads taking float and float1, but trying to
invoke these functions yields an "ambiguous function call" error.]
* introduce new (semi-)generic types. This is far more code and ends up acting
like our current scheme (with helpers) in a slightly more complex form.
So I think we can go ahead and rip out this vestige of the original design for
intrinsics.
As for why to change it: rbtrees are simply more complex to deal with, and it
seems unlikely to me that the difference is going to matter. I do not expect any
program to define large quantities of intrinsics; linked list search should be
good enough.
This field is now analogous to vkd3d_shader_register_index.rel_addr.
Also, it makes sense to rename it now because all the constant part of
the offset is now handled to hlsl_deref.const_offset. Consequently, it
may also be NULL now.
