AD: Fixed do-while loops (#2683)

* WIP: Fix for do-while loops

* Added a somewhat hacky fix for do-while loops

* Redid the indexed region map builder step to fix issue with the nested loops test

* rename

* Used managed pointers

2 files changed, 53 insertions, 0 deletions

diff --git a/tests/autodiff/reverse-do-while.slang b/tests/autodiff/reverse-do-while.slang
new file mode 100644
index 000000000..983863f5e
--- /dev/null
+++ b/tests/autodiff/reverse-do-while.slang
@@ -0,0 +1,47 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX:-cpu -compute -output-using-type -shaderobj
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+typedef DifferentialPair<float> dpfloat;
+typedef float.Differential dfloat;
+
+[BackwardDifferentiable]
+float test_simple_while(float y)
+{
+    float t = y;
+
+    bool keepGoing = true;
+    int i = 2;
+
+    [MaxIters(3)]
+    do 
+    {
+        i++;
+        t = t * t;
+
+        keepGoing = (i < 5);
+    } while (keepGoing);
+
+    return t;
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    {
+        dpfloat dpa = dpfloat(1.0, 0.0);
+
+        __bwd_diff(test_simple_while)(dpa, 1.0f);
+        outputBuffer[0] = dpa.d; // Expect: 8.0
+    }
+
+    {
+        dpfloat dpa = dpfloat(0.4, 0.0);
+
+        __bwd_diff(test_simple_while)(dpa, 1.0f);
+        outputBuffer[1] = dpa.d; // Expect: 0.0131072
+    }
+}
diff --git a/tests/autodiff/reverse-do-while.slang.expected.txt b/tests/autodiff/reverse-do-while.slang.expected.txt
new file mode 100644
index 000000000..76b7cf779
--- /dev/null
+++ b/tests/autodiff/reverse-do-while.slang.expected.txt
@@ -0,0 +1,6 @@
+type: float
+8.000000
+0.013107
+0.000000
+0.000000
+0.000000