Feature/dx12 (#469)

* Fix signed/unsigned comparison warning.

* Split out d3d functions that will work across dx11 and 12.

* Improve slang-test/README.md around command line options.

* Make Guid comparison honor alignment for comparisons, such that mechanism work on architectures that can only do aligned accesses.

* Initial setup of D3D12 Renderer, with presentFrame and clearFrame.

* More support for D3D12

* Added FreeList
* Added D3D12CircularResourceHeap
* First attempt at createBuffer

* First pass at map/unmap.

* First pass binding vertex/constant buffers, and setting up InputLayout. Note that memory is not kept in scope on binding yet.

* First pass of D3DDescriptorHeap

* Small tidy up in render-d3d11. Added D3DDescriptorHeap to project.

* First pass at D3D12 bind state.

* Fix typos in D3D12Resource

* Tidy up Dx11 render binding a little to match more with Dx12 style.

* First pass at Dx12 BindingState

* Handling of the command list d3d12. Support for submitGpuWork and waitForGpu.

* First attempt at Dx12 capture of backbuffer to file.

* First attempt at D3D12 binding for graphics.

* D3D12 setup viewport etc - does now render triangle in render0.hlsl.

* First pass at support for compute on D3D12Renderer

* Use spaces over tabs in D3DUtil

* Tabs to spaces in D3D12DescriptorHeap

* Convert tab->spaces on render-d3d12.cpp

1 files changed, 8 insertions, 11 deletions

diff --git a/source/core/slang-com-ptr.h b/source/core/slang-com-ptr.h
index 729b6b266..9f6651306 100644
--- a/source/core/slang-com-ptr.h
+++ b/source/core/slang-com-ptr.h
@@ -51,21 +51,18 @@ struct Guid
 
 SLANG_FORCE_INLINE bool operator==(const Guid& aIn, const Guid& bIn)
 {
+	// Use the largest type the honors the alignment of Guid
+	typedef uint32_t CmpType;
     struct GuidCompare
     {
-        enum { kNum = sizeof(Guid) / sizeof(size_t) };
         Guid guid;
-        size_t data[kNum];
+		CmpType data[sizeof(Guid) / sizeof(CmpType)];
     };
-    const GuidCompare& a = reinterpret_cast<const GuidCompare&>(aIn);
-    const GuidCompare& b = reinterpret_cast<const GuidCompare&>(bIn);
-    
-    switch (GuidCompare::kNum)
-    {
-        case 2:     return ((a.data[0] ^ b.data[0]) | (a.data[1] ^ b.data[1])) == 0;   
-        case 4:     return ((a.data[0] ^ b.data[0]) | (a.data[1] ^ b.data[1]) | (a.data[2] ^ b.data[2]) | (a.data[3] ^ b.data[3]) ) == 0;   
-        default:    return false;
-    }
+	// Type pun - so compiler can 'see' the pun and not break aliasing rules 
+    const CmpType* a = reinterpret_cast<const GuidCompare&>(aIn).data;
+    const CmpType* b = reinterpret_cast<const GuidCompare&>(bIn).data;
+	// Make the guid comparison a single branch, by not using short circuit
+	return ((a[0] ^ b[0]) | (a[1] ^ b[1]) | (a[2] ^ b[2]) | (a[3] ^ b[3])) == 0;
 } 
 
 SLANG_FORCE_INLINE bool operator!=(const Guid& a, const Guid& b)