[clang] [HLSL][Matrix] Add support for Matrix element and trunc Casts (PR #168915)

[Sarah Spall via cfe-commits]

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@@ -2102,6 +2105,57 @@ static bool IsVectorElementConversion(Sema &S, QualType FromType,
   return false;
 }
 
+/// Determine whether the conversion from FromType to ToType is a valid
+/// matrix conversion.
+///
+/// \param ICK Will be set to the matrix conversion kind, if this is a matrix
+/// conversion.
+static bool IsMatrixConversion(Sema &S, QualType FromType, QualType ToType,
+                               ImplicitConversionKind &ICK,
+                               ImplicitConversionKind &ElConv, Expr *From,
+                               bool InOverloadResolution, bool CStyle) {
+  // Implicit conversions for matrices are an HLSL feature not present in C/C++.
+  if (!S.getLangOpts().HLSL)
+    return false;
+
+  auto *ToMatrixType = ToType->getAs<ConstantMatrixType>();
+  auto *FromMatrixType = FromType->getAs<ConstantMatrixType>();
+
+  // If both arguments are vectors, handle possible vector truncation and
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spall wrote:

is this meant to say matrices and not vectors?

https://github.com/llvm/llvm-project/pull/168915