Fix issue with transposing `IRMakeVector` with non-singleton operands (#3280)

3 files changed, 50 insertions, 2 deletions

diff --git a/source/slang/slang-ir-autodiff-transpose.h b/source/slang/slang-ir-autodiff-transpose.h
index bcebd2108..a3a4eb2b3 100644
--- a/source/slang/slang-ir-autodiff-transpose.h
+++ b/source/slang/slang-ir-autodiff-transpose.h
@@ -1841,6 +1841,7 @@ struct DiffTransposePass
     TranspositionResult transposeMakeVector(IRBuilder* builder, IRInst* fwdMakeVector, IRInst* revValue)
     {
         List<RevGradient> gradients;
+        UInt offset = 0;
         for (UIndex ii = 0; ii < fwdMakeVector->getOperandCount(); ii++)
         {
             auto argOperand = fwdMakeVector->getOperand(ii);
@@ -1857,12 +1858,12 @@ struct DiffTransposePass
                 gradAtIndex = builder->emitElementExtract(
                     argOperand->getDataType(),
                     revValue,
-                    builder->getIntValue(builder->getIntType(), ii));
+                    builder->getIntValue(builder->getIntType(), offset));
             }
             else
             {
                 ShortList<UInt> componentIndices;
-                for (UInt index = ii; index < ii + componentCount; index++)
+                for (UInt index = offset; index < offset + componentCount; index++)
                     componentIndices.add(index);
                 gradAtIndex = builder->emitSwizzle(
                     argOperand->getDataType(),
@@ -1876,6 +1877,8 @@ struct DiffTransposePass
                 fwdMakeVector->getOperand(ii),
                 gradAtIndex,
                 fwdMakeVector));
+            
+            offset += componentCount;
         }
 
         // (A = float3(X, Y, Z)) -> [(dX += dA), (dY += dA), (dZ += dA)]
diff --git a/tests/autodiff/make-array-non-uniform.slang b/tests/autodiff/make-array-non-uniform.slang
new file mode 100644
index 000000000..2cdedb864
--- /dev/null
+++ b/tests/autodiff/make-array-non-uniform.slang
@@ -0,0 +1,39 @@
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX:-vk -compute -shaderobj -output-using-type
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+typedef DifferentialPair<float2> dpfloat2;
+typedef DifferentialPair<float3> dpfloat3;
+typedef DifferentialPair<float4> dpfloat4;
+
+[Differentiable]
+float4 f(float4 x)
+{
+    return float4(x.rgb, x.a * x.a);
+}
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    {
+        float4 a = float4(1.0, 2.0, 3.0, 4.0);
+        float4 da = float4(1.0, 0.5, 1.5, 2.5);
+
+        outputBuffer[0] = fwd_diff(f)(dpfloat4(a, da)).d.x;
+    }
+
+    {
+        float4 a = float4(1.0, 2.0, 3.0, 4.0);
+        
+        var dpa = diffPair(a);
+
+        bwd_diff(f)(dpa, float4(1.0, 0.5, 1.5, 2.5));
+
+        outputBuffer[1] = dpa.d.x; // 1.0
+        outputBuffer[2] = dpa.d.y; // 0.5
+        outputBuffer[3] = dpa.d.z; // 0.0
+        outputBuffer[4] = dpa.d.a; // 0.0
+    }
+}
diff --git a/tests/autodiff/make-array-non-uniform.slang.expected.txt b/tests/autodiff/make-array-non-uniform.slang.expected.txt
new file mode 100644
index 000000000..ba5428fd7
--- /dev/null
+++ b/tests/autodiff/make-array-non-uniform.slang.expected.txt
@@ -0,0 +1,6 @@
+type: float
+1.000000
+1.000000
+0.500000
+1.500000
+20.000000