From d58e08f8237a1888ceaad53402d534679ea83b1a Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 18 Nov 2022 12:37:27 -0800
Subject: Data flow validation pass for diagnosing derivative loss. (#2523)

---
 tests/diagnostics/autodiff-data-flow.slang         | 38 ++++++++++++++++++++++
 .../diagnostics/autodiff-data-flow.slang.expected  | 11 +++++++
 tests/diagnostics/autodiff.slang                   | 27 +++++++++++++++
 tests/diagnostics/autodiff.slang.expected          | 14 ++++++++
 4 files changed, 90 insertions(+)
 create mode 100644 tests/diagnostics/autodiff-data-flow.slang
 create mode 100644 tests/diagnostics/autodiff-data-flow.slang.expected
 create mode 100644 tests/diagnostics/autodiff.slang
 create mode 100644 tests/diagnostics/autodiff.slang.expected

(limited to 'tests/diagnostics')

diff --git a/tests/diagnostics/autodiff-data-flow.slang b/tests/diagnostics/autodiff-data-flow.slang
new file mode 100644
index 000000000..93c76c07e
--- /dev/null
+++ b/tests/diagnostics/autodiff-data-flow.slang
@@ -0,0 +1,38 @@
+//DIAGNOSTIC_TEST:SIMPLE:
+
+float nonDiff(float x)
+{
+    return x;
+}
+
+[ForwardDifferentiable]
+float f(float x)
+{
+    float val = 0;
+    if (x > 5)
+        val = x + 1;
+    else
+        val = nonDiff(x * 2.0f);
+    // Not all path propagates derivatives through.
+    return val;
+}
+
+// error: function does not return a differentiable value.
+[ForwardDifferentiable]
+void g(float x)
+{
+    float val = 0;
+    if (x > 5)
+        val = x + 1;
+    return;
+}
+
+
+[ForwardDifferentiable]
+float h(float x)
+{
+    float val = 0;
+    // no diagnostic by clarifying intention.
+    val = no_diff(nonDiff(x * 2.0f));
+    return val;
+}
diff --git a/tests/diagnostics/autodiff-data-flow.slang.expected b/tests/diagnostics/autodiff-data-flow.slang.expected
new file mode 100644
index 000000000..869ce42b3
--- /dev/null
+++ b/tests/diagnostics/autodiff-data-flow.slang.expected
@@ -0,0 +1,11 @@
+result code = -1
+standard error = {
+tests/diagnostics/autodiff-data-flow.slang(15): error 41020: derivative cannot be propagated through call to non-differentiable function `nonDiff`, use 'no_diff' to clarify intention.
+        val = nonDiff(x * 2.0f);
+                     ^
+tests/diagnostics/autodiff-data-flow.slang(22): error 41021: a differentiable function must have at least one differentiable output.
+void g(float x)
+     ^
+}
+standard output = {
+}
diff --git a/tests/diagnostics/autodiff.slang b/tests/diagnostics/autodiff.slang
new file mode 100644
index 000000000..f9fed6753
--- /dev/null
+++ b/tests/diagnostics/autodiff.slang
@@ -0,0 +1,27 @@
+//DIAGNOSTIC_TEST:SIMPLE:
+
+float nonDiff(float x)
+{
+    return x;
+}
+
+[ForwardDifferentiable]
+float f(float x)
+{
+    float val = 0;
+    if (x > 5)
+        val = x + 1;
+    return val;
+}
+
+[ForwardDifferentiable]
+float m(float x)
+{
+    float x1 = no_diff x; // invalid use of no_diff here.
+    return no_diff f(x);  // no_diff on a differentiable call has no meaning.
+}
+
+float n(float x)
+{
+    return no_diff nonDiff(x); // no_diff in a non-differentiable function
+}
\ No newline at end of file
diff --git a/tests/diagnostics/autodiff.slang.expected b/tests/diagnostics/autodiff.slang.expected
new file mode 100644
index 000000000..cd97bce76
--- /dev/null
+++ b/tests/diagnostics/autodiff.slang.expected
@@ -0,0 +1,14 @@
+result code = -1
+standard error = {
+tests/diagnostics/autodiff.slang(20): error 38031: 'no_diff' can only be used to decorate a call.
+    float x1 = no_diff x; // invalid use of no_diff here.
+               ^~~~~~~
+tests/diagnostics/autodiff.slang(21): error 38032: use 'no_diff' on a call to a differentiable function has no meaning.
+    return no_diff f(x);  // no_diff on a differentiable call has no meaning.
+           ^~~~~~~
+tests/diagnostics/autodiff.slang(26): error 38033: cannot use 'no_diff' in a non-differentiable function.
+    return no_diff nonDiff(x); // no_diff in a non-differentiable function
+           ^~~~~~~
+}
+standard output = {
+}
-- 
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