Fix ICE when immutable value is passed to a bwd_diff function. (#7973)

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/diagnostics/lvalue-in-bwd-diff.slang b/tests/diagnostics/lvalue-in-bwd-diff.slang
new file mode 100644
index 000000000..2e12bf5c0
--- /dev/null
+++ b/tests/diagnostics/lvalue-in-bwd-diff.slang
@@ -0,0 +1,23 @@
+//TEST:SIMPLE(filecheck=CHECK): -target spirv
+[Differentiable]
+float square(float x, float y)
+{
+    return x * x + y * y;
+}
+
+void main()
+{
+    // Forward mode differentiation
+    let x = diffPair(3.0, 1.0); // x = 3, 𝜕x/𝜕𝛉 = 1
+    let y = diffPair(4.0, 1.0); // y = 4, 𝜕y/𝜕𝛄 = 1
+    let result = fwd_diff(square)(x, y);
+    printf("dResult: %f\n", result.d);
+
+    // Backward mode differentiation
+    let dLdSquare = 1.0f;
+    // CHECK-NOT: error 30049
+    // CHECK: error 30047
+    // CHECK-NOT: error 30049
+    bwd_diff(square)(x, y, dLdSquare);
+    printf("dL/dx: %f, dL/dy: %f\n", x.d, y.d);
+}