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

1 files changed, 5 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)]