Add `[ForwardDerivativeOf]` attribute. (#2501)

* Add [ForwardDerivativeOf] attribute.

* Fix handling around phi nodes.

* Fixes.

* Remove IR opcode for ForwardDerivativeOfDecoration.

Co-authored-by: Yong He <yhe@nvidia.com>

4 files changed, 47 insertions, 4 deletions

diff --git a/tests/autodiff/custom-intrinsic-2.slang b/tests/autodiff/custom-intrinsic-2.slang
new file mode 100644
index 000000000..0a2fd9c0b
--- /dev/null
+++ b/tests/autodiff/custom-intrinsic-2.slang
@@ -0,0 +1,37 @@
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+typedef DifferentialPair<float> dpfloat;
+ 
+float f(float x)
+{
+    return x*x;
+}
+
+[ForwardDerivativeOf(f)]
+DifferentialPair<float> df(DifferentialPair<float> x)
+{
+    var primal = x.p * x.p;
+    var diff = 2 * x.p * x.d;
+    return DifferentialPair<float>(primal, diff);
+}
+
+[ForwardDifferentiable]
+float g(float x)
+{
+    return f(x);
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    {
+        dpfloat dpa = dpfloat(3.0, 1.0);
+
+        outputBuffer[0] = f(dpa.p);        // Expect: 9.0
+        outputBuffer[1] = __fwd_diff(g)(dpa).d; // Expect: 6.0
+    }
+}
diff --git a/tests/autodiff/custom-intrinsic-2.slang.expected.txt b/tests/autodiff/custom-intrinsic-2.slang.expected.txt
new file mode 100644
index 000000000..5483a4781
--- /dev/null
+++ b/tests/autodiff/custom-intrinsic-2.slang.expected.txt
@@ -0,0 +1,6 @@
+type: float
+9.000000
+6.000000
+0.000000
+0.000000
+0.000000
diff --git a/tests/autodiff/dstdlib-vector.slang b/tests/autodiff/dstdlib-vector.slang
index 1a1bd0dfa..ba66f0756 100644
--- a/tests/autodiff/dstdlib-vector.slang
+++ b/tests/autodiff/dstdlib-vector.slang
@@ -10,7 +10,7 @@ typedef DifferentialPair<float> dpfloat;
 float f(float x)
 {
     float3 vx = float3(x, 2*x, 3*x);
-    float3 vexpx = dstd.exp(vx);
+    float3 vexpx = exp(vx);
     return vexpx.x + vexpx.y + vexpx.z;
 }
 
diff --git a/tests/autodiff/dstdlib.slang b/tests/autodiff/dstdlib.slang
index 247200511..b96cd3c51 100644
--- a/tests/autodiff/dstdlib.slang
+++ b/tests/autodiff/dstdlib.slang
@@ -9,19 +9,19 @@ typedef DifferentialPair<float> dpfloat;
 [ForwardDifferentiable]
 float f(float x)
 {
-    return dstd.exp(x);
+    return exp(x);
 }
 
 [ForwardDifferentiable]
 float g(float x)
 {
-    return dstd.sin(x);
+    return sin(x);
 }
 
 [ForwardDifferentiable]
 float h(float x)
 {
-    return dstd.cos(x);
+    return cos(x);
 }
 
 [numthreads(1, 1, 1)]