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, 10 insertions, 4 deletions

diff --git a/tools/render-test/cpu-compute-util.cpp b/tools/render-test/cpu-compute-util.cpp
index 7c9103cb3..6682eef1a 100644
--- a/tools/render-test/cpu-compute-util.cpp
+++ b/tools/render-test/cpu-compute-util.cpp
@@ -52,15 +52,15 @@ struct ValueTexture : public CPUComputeUtil::Resource, public CPPPrelude::ITextu
     {
         return _calcMipDims(mipLevel, m_dims);
     }
-    virtual void Load(const int32_t* loc, void* out) SLANG_OVERRIDE
+    virtual void Load(const int32_t* loc, void* out, size_t dataSize) SLANG_OVERRIDE
     {
         _set(out);
     }
-    virtual void Sample(CPPPrelude::SamplerState samplerState, const float* loc, void* out) SLANG_OVERRIDE
+    virtual void Sample(CPPPrelude::SamplerState samplerState, const float* loc, void* out, size_t dataSize) SLANG_OVERRIDE
     {
         _set(out);
     }
-    virtual void SampleLevel(CPPPrelude::SamplerState samplerState, const float* loc, float level, void* out) SLANG_OVERRIDE
+    virtual void SampleLevel(CPPPrelude::SamplerState samplerState, const float* loc, float level, void* out, size_t dataSize) SLANG_OVERRIDE
     {
         _set(out);
     }
@@ -201,9 +201,15 @@ struct FloatRWTexture : public CPUComputeUtil::Resource, public CPPPrelude::IRWT
     {
         return _calcMipDims(mipLevel, m_dims);
     }
-    virtual void Load(const int32_t* loc, void* out) SLANG_OVERRIDE { m_data.getAt((const uint32_t*)loc, (float*)out); }
+    virtual void Load(const int32_t* loc, void* out, size_t dataSize) SLANG_OVERRIDE { m_data.getAt((const uint32_t*)loc, (float*)out); }
     virtual void* refAt(const uint32_t* loc) SLANG_OVERRIDE { return m_data.getAt(loc); }
 
+    virtual void Sample(CPPPrelude::SamplerState samplerState, const float* loc, void* out, size_t dataSize) SLANG_OVERRIDE
+    {}
+
+    virtual void SampleLevel(CPPPrelude::SamplerState samplerState, const float* loc, float level, void* out, size_t dataSize) SLANG_OVERRIDE
+    {}
+
     FloatRWTexture(int elementCount, const CPPPrelude::TextureDimensions& inDims, float initialValue):
         m_dims(inDims)
     {