Fix crash during emitCast of attributed type, allow MaxIters to take linktime const. (#5791)

* Fix crash during emitCast of attributed type.

* Allow [MaxIters] to take link time constants.

---------

Co-authored-by: Ellie Hermaszewska <ellieh@nvidia.com>

2 files changed, 72 insertions, 0 deletions

diff --git a/tests/bugs/gh-5781.slang b/tests/bugs/gh-5781.slang
new file mode 100644
index 000000000..33456f500
--- /dev/null
+++ b/tests/bugs/gh-5781.slang
@@ -0,0 +1,57 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+// CHECK: OpEntryPoint
+
+module test;
+
+public enum class MaterialID : uint { invalid = 0xffffffff };
+
+public struct Material : IDifferentiable
+{
+    float x;
+}
+
+public struct Hit
+{
+    MaterialID material;
+}
+
+public struct Scene
+{
+    StructuredBuffer<Material> materials;
+    RWStructuredBuffer<Material> grads;
+
+    [Differentiable]
+    Material load(MaterialID id) { return materials[uint(id)]; }
+
+    void accumulate(MaterialID id, Material d) { grads[uint(id)].x += d.x; }
+
+    [Differentiable, BackwardDerivative(_get_material_bwd)]
+    public Material get_material(MaterialID id) { return load(id); }
+
+    public void _get_material_bwd(MaterialID id, Material d) { accumulate(id, d); }
+
+    [Differentiable]
+    public Material get_material(Hit hit) { return get_material(hit.material); }
+}
+
+[Differentiable]
+float trace(const Scene scene, Hit hit)
+{
+    Material m = scene.get_material(hit);
+    return m.x;
+}
+
+
+[shader("compute")]
+void main(
+    uniform Scene scene,
+    uniform StructuredBuffer<uint> input,
+    uniform RWStructuredBuffer<float> output,
+    uniform RWStructuredBuffer<float> grads
+)
+{
+    Hit hit;
+    hit.material = MaterialID(input[0]);
+    output[0] = trace(scene, hit);
+    bwd_diff(trace)(scene, hit, grads[0]);
+}
\ No newline at end of file
diff --git a/tests/language-feature/constants/max-iters-link-time-const.slang b/tests/language-feature/constants/max-iters-link-time-const.slang
new file mode 100644
index 000000000..cf1ccbbd1
--- /dev/null
+++ b/tests/language-feature/constants/max-iters-link-time-const.slang
@@ -0,0 +1,15 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+// CHECK: OpEntryPoint
+
+extern static const int num = 10;
+RWStructuredBuffer<float> outputBuffer;
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    [MaxIters(num)]
+    for (int i = 0; i < num; i++)
+    {
+        outputBuffer[i] = i;
+    }
+}