Add a CPU renderer implementation (#1750)

* Add a CPU renderer implementation

This change adds a CPU back-end to `gfx` and ensures that most of our existing CPU tests pass when using it.

Detailed notes:

* Most of the CPU renderer implementation is copy-pasted from the CUDA case, so they share a lot of similar logic

* The main addition to the CPU renderer is a semi-complete implementation of host-memory textures. The logic here handles all the main shapes (Buffer, 1D, 2D, 3D, Cube) and all the currently-supported `Format`s that are sample-able as-is (no D24S8). The implementation is not intended to be fast, and it currently only does nearest-neighbor sampling, but otherwise it tries to avoid cutting too many corners and should be ar reasonable starting point for a more complete (but not performance-oriented) implementation.

* Refactored the CPU prelude `IRWTexture` interface to inherit from `ITexture`, since in most cases a single type will end up implementing both. It might be worth it to collapse it all down to a single interface later.

* Changed the CPU prelude `ITexture`/`IRWTexture` interface so that it takes both a pointer *and* a size for output arguments. This change seems necessary to allow a shader variable declared as a `Texture2D<float>` to fetch a single `float` when the underlying texture might be using RGBA32F.

* Added to the `IComponentType` public API so that we can query a "host callable" for an entry point and not just a binary.

* Turned off the `-shaderobj` flag on two tests that weren't yet compatible with shader objects but still had the flag left in on the path (since previously the CPU path always used the non-`gfx` non-shader-object logic anyway)

* Disabled one test (`dynamic-dispatch-11`) that relied on the `ConstantBuffer<IInterface>` idiom that we know we are planning to chagne soon anyway.

* Made a few changes to the CUDA path to bring it into line with what I added for the CPU path. These were mostly bug fixes around indexing logic for sub-objects and resources.

* fixup

1 files changed, 17 insertions, 0 deletions

diff --git a/slang.h b/slang.h
index f0abc135a..b354e6b12 100644
--- a/slang.h
+++ b/slang.h
@@ -4055,6 +4055,23 @@ namespace slang
             virtual SLANG_NO_THROW SlangResult SLANG_MCALL link(
                 IComponentType**            outLinkedComponentType,
                 ISlangBlob**                outDiagnostics = nullptr) = 0;
+
+                /** Get entry point 'callable' functions accessible through the ISlangSharedLibrary interface.
+
+                The functions remain in scope as long as the ISlangSharedLibrary interface is in scope.
+
+                NOTE! Requires a compilation target of SLANG_HOST_CALLABLE.
+    
+                @param entryPointIndex  The index of the entry point to get code for.
+                @param targetIndex      The index of the target to get code for (default: zero).
+                @param outSharedLibrary A pointer to a ISharedLibrary interface which functions can be queried on.
+                @returns                A `SlangResult` to indicate success or failure.
+                */
+            virtual SLANG_NO_THROW SlangResult SLANG_MCALL getEntryPointHostCallable(
+                int                     entryPointIndex,
+                int                     targetIndex,
+                ISlangSharedLibrary**   outSharedLibrary,
+                slang::IBlob**          outDiagnostics = 0) = 0;
     };
     #define SLANG_UUID_IComponentType { 0x5bc42be8, 0x5c50, 0x4929, { 0x9e, 0x5e, 0xd1, 0x5e, 0x7c, 0x24, 0x1, 0x5f } };