Fix tests\autodiff\reverse-while-loop-3.slang test (shader-slang#4886)

* Fix `tests\autodiff\reverse-while-loop-3.slang` test

Fixes: shader-slang#4876

Fix `tests\autodiff\reverse-while-loop-3.slang` test to have correct listed output values

* set default to 1 (different val)

---------

Co-authored-by: Yong He <yonghe@outlook.com>

tests/autodiff/reverse-while-loop-3.slang

@@ -1,12 +1,12 @@
-//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(compute):COMPARE_COMPUTE_EX(filecheck-buffer=BUF):-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=BUF):-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=BUF):-cpu -compute -output-using-type -shaderobj
 
-//TEST_INPUT:ubuffer(data=[0 0 0 0 0], stride=4):out,name=outputBuffer
+//TEST_INPUT:ubuffer(data=[1], stride=4):out,name=outputBuffer
 RWStructuredBuffer<float> outputBuffer;
 
 // This test isn't actually testing the output, but rather that the compiler doesn't crash upon 
-// encountering a specific loop pattern. ('Data' is non-differentiable here, so the expected output is 0)s
+// encountering a specific loop pattern. ('Data' is non-differentiable here, so the expected output is 0)
 // 
 
 typedef DifferentialPair<float> dpfloat;
@@ -21,6 +21,10 @@ struct P
 
 struct Data
 {
+    __init(float dataIn)
+    {
+        this.t = dataIn;
+    }
     float t;
 };
 
@@ -32,7 +36,7 @@ void updateData(Data data)
 [BackwardDifferentiable]
 float test_simple_while(float y, uint n)
 {
-    Data d = { y };
+    Data d = Data(y);
     P p;
     p.terminated = false;
     int i = n;
@@ -61,6 +65,7 @@ void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
         dpfloat dpa = dpfloat(1.0, 0.0);
 
         __bwd_diff(test_simple_while)(dpa, 2, 1.0f);
-        outputBuffer[0] = dpa.d; // Expect: 8.0
+        outputBuffer[0] = dpa.d;
+        //BUF: 0
     }
 }