[WGSL] Add support for matrix subtraction

https://bugs.webkit.org/show_bug.cgi?id=264406
rdar://118117794

Reviewed by Mike Wyrzykowski.

The TypeDeclarations file was missing the subtraction overload for matrices. Add
the missing overload and implement constant matrix subtraction as well.

* Source/WebGPU/WGSL/ConstantFunctions.h:
(WGSL::CONSTANT_FUNCTION):
* Source/WebGPU/WGSL/TypeDeclarations.rb:
* Source/WebGPU/WGSL/tests/valid/overload.wgsl:

Canonical link: https://commits.webkit.org/270428@main

Source/WebGPU/WGSL/ConstantFunctions.h

@@ -442,6 +442,18 @@ CONSTANT_FUNCTION(Minus)
             return -arg;
         });
     }
+
+    if (auto* left = std::get_if<ConstantMatrix>(&arguments[0])) {
+        auto& right = std::get<ConstantMatrix>(arguments[1]);
+        auto* elementType = std::get<Types::Matrix>(*resultType).element;
+        ASSERT(left->columns == right.columns);
+        ASSERT(left->rows == right.rows);
+        ConstantMatrix result(left->columns, left->rows);
+        for (unsigned i = 0; i < result.elements.size(); ++i)
+            CALL_MOVE(result.elements[i], Minus, elementType, { left->elements[i], right.elements[i] });
+        return { { result } };
+    }
+
     return constantBinaryOperation<Constraints::Number>(arguments, [&](auto left, auto right) {
         return left - right;
     });

Source/WebGPU/WGSL/TypeDeclarations.rb

@@ -46,6 +46,7 @@
     [T < Number, N].(vec[N][T], T) => vec[N][T],
     [T < Number, N].(T, vec[N][T]) => vec[N][T],
     [T < Number, N].(vec[N][T], vec[N][T]) => vec[N][T],
+    [T < Float, C, R].(mat[C,R][T], mat[C,R][T]) => mat[C,R][T],
 }
 
 operator :*, {

Source/WebGPU/WGSL/tests/valid/overload.wgsl

@@ -103,6 +103,7 @@ fn testBinaryMinus() {
   _ = vec2(1, 1) - 1;
   _ = 1 - vec2(1, 1);
   _ = vec2(1, 1) - vec2(1, 1);
+  _ = mat2x2(2, 2, 2, 2) - mat2x2(1, 1, 1, 1);
 }
 
 fn testComparison() {