Add `IDifferentiablePtrType` support for arrays (#5576)

* Add `IDifferentiablePtrType` support for arrays

- Also fixes an issue with spirv-emit of constructors that contain references to global params

* Fix GLSL legalization for arrays of resource types

1 files changed, 59 insertions, 0 deletions

diff --git a/tests/autodiff/diff-ptr-type-array.slang b/tests/autodiff/diff-ptr-type-array.slang
new file mode 100644
index 000000000..30e6fe963
--- /dev/null
+++ b/tests/autodiff/diff-ptr-type-array.slang
@@ -0,0 +1,59 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -vk -shaderobj -output-using-type
+//DISABLE_TEST(compute):COMPARE_COMPUTE:-wgpu
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+// ----- MyPtrType definition -----
+struct MyPtrType : IDifferentiablePtrType
+{
+    typealias Differential = MyPtrType;
+
+    RWStructuredBuffer<float> buffer;
+    uint offset;
+
+    float load(uint idx) { return buffer[offset + idx]; }
+    void accumulate(uint idx, float value) { buffer[offset + idx] += value; }
+}
+
+[BackwardDerivative(load_bwd)]
+float load(MyPtrType[2] b, uint idx)
+{
+    return b[1].load(idx);
+}
+
+void load_bwd(DifferentialPtrPair<MyPtrType[2]> b, uint idx, float grad)
+{
+    b.d[1].accumulate(idx, grad);
+}
+
+// ------
+[Differentiable]
+float reduce(MyPtrType a)
+{
+    return load( { a, a }, 0) + load( { a, a }, 1);
+}
+
+[Differentiable]
+float test(MyPtrType b)
+{
+    return reduce(b);
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint id: SV_DispatchThreadID)
+{
+    outputBuffer[0] = 1; // CHECK: 1
+    outputBuffer[1] = 2; // CHECK: 2
+
+    // Denote the first two elements in the buffer as the primal buffer and the last two elements
+    // for the derivative.
+    var b = DifferentialPtrPair<MyPtrType>( { outputBuffer, 0 }, { outputBuffer, 2 });
+
+    bwd_diff(test)(b, 1.5f);
+
+    // Check locations [2] and [3] in the buffer
+    // CHECK: 1.5
+    // CHECK: 1.5
+}