Fix unzipping logic for inout non-diff parameters and adjust tests (#4090)

* Fix unzipping logic for inout non-diff parameters and adjust tests

+ Removed `-g0` from `struct-this-parameter.slang` test. Works correctly with the new unzipping logic.
+ Removed `-g0` from `was/warped-sampling-1d.slang` test. Works correctly with DX12 & CS_5_1. CS_5_0 appears to run into an FXC compiler bug with detecting infinite loops where there don't appear to be any.

* Update slang-ir-autodiff-unzip.h

* Update warped-sampling-1d.slang

1 files changed, 25 insertions, 3 deletions

diff --git a/source/slang/slang-ir-autodiff-unzip.h b/source/slang/slang-ir-autodiff-unzip.h
index c57dc300f..771a3977e 100644
--- a/source/slang/slang-ir-autodiff-unzip.h
+++ b/source/slang/slang-ir-autodiff-unzip.h
@@ -372,10 +372,32 @@ struct DiffUnzipPass
             }
             else
             {
-                // For non differentiable arguments, we can simply pass the argument as is
-                // if this isn't a `out` parameter, in which case it is removed from propagate call.
-                if (!as<IROutType>(arg->getDataType()))
+                if (auto inOutType = as<IRInOutType>(resolvedPrimalFuncType->getParamType(ii)))
+                {
+                    // For 'inout' parameter we need to create a temp var to hold the value
+                    // before the primal call. This logic is similar to the 'inout' case for differentiable params
+                    // only we don't need to deal with pair types.
+                    //
+                    auto tempPrimalVar = primalBuilder->emitVar(as<IRPtrTypeBase>(arg->getDataType())->getValueType());
+
+                    auto storeUse = findUniqueStoredVal(cast<IRVar>(arg));
+                    auto storeInst = cast<IRStore>(storeUse->getUser());
+                    auto storedVal = storeInst->getVal();
+
+                    primalBuilder->emitStore(tempPrimalVar, storedVal);
+
+                    diffArgs.add(tempPrimalVar);
+                }
+                else
+                {
+                    // For pure 'in' type. Simply re-use the original argument inst.
+                    //
+                    // For 'out' type parameters, it doesn't really matter what we pass in here, since
+                    // the tranposition logic will discard the argument anyway (we'll pass in the old arg, 
+                    // just to keep the number of arguments consistent)
+                    // 
                     diffArgs.add(arg);
+                }
             }
         }