From e7df8538eb8f0ed06f0838d946bec8e9e0fe0985 Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Thu, 1 Dec 2022 18:55:43 -0800
Subject: Allow `no_diff` on `this` parameter. (#2543)

---
 source/slang/slang-ir-autodiff.cpp | 59 ++++++++++++++++++++++++++------------
 1 file changed, 40 insertions(+), 19 deletions(-)

(limited to 'source/slang/slang-ir-autodiff.cpp')

diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index 5b5832073..86429f9ba 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -27,6 +27,20 @@ IRInst* _lookupWitness(IRBuilder* builder, IRInst* witness, IRInst* requirementK
     return nullptr;
 }
 
+bool isNoDiffType(IRType* paramType)
+{
+    while (auto ptrType = as<IRPtrTypeBase>(paramType))
+        paramType = ptrType->getValueType();
+    while (auto attrType = as<IRAttributedType>(paramType))
+    {
+        if (attrType->findAttr<IRNoDiffAttr>())
+        {
+            return true;
+        }
+    }
+    return false;
+}
+
 IRStructField* DifferentialPairTypeBuilder::findField(IRInst* type, IRStructKey* key)
 {
     if (auto irStructType = as<IRStructType>(type))
@@ -80,19 +94,14 @@ IRInst* DifferentialPairTypeBuilder::emitFieldAccessor(IRBuilder* builder, IRIns
     IRInst* pairType = nullptr;
     if (auto basePtrType = as<IRPtrTypeBase>(baseInst->getDataType()))
     {
-        auto baseTypeInfo = lowerDiffPairType(builder, basePtrType->getValueType());
+        auto loweredType = lowerDiffPairType(builder, basePtrType->getValueType());
 
-        // TODO(sai): Not sure at the moment how to handle diff-bottom pointer types,
-        // especially since we probably don't need diff bottom anymore.
-        // 
-        SLANG_ASSERT(!baseTypeInfo.isTrivial);
-
-        pairType = builder->getPtrType(kIROp_PtrType, (IRType*)baseTypeInfo.loweredType);
+        pairType = builder->getPtrType(kIROp_PtrType, (IRType*)loweredType);
     }
     else
     {
-        auto baseTypeInfo = lowerDiffPairType(builder, baseInst->getDataType());
-        pairType = baseTypeInfo.loweredType;
+        auto loweredType = lowerDiffPairType(builder, baseInst->getDataType());
+        pairType = loweredType;
     }
 
     if (auto basePairStructType = as<IRStructType>(pairType))
@@ -240,33 +249,29 @@ IRInst* DifferentialPairTypeBuilder::getDiffTypeWitnessFromPairType(IRBuilder* b
     return _lookupWitness(builder, witnessTable, sharedContext->differentialAssocTypeWitnessStructKey);
 }
 
-DifferentialPairTypeBuilder::LoweredPairTypeInfo DifferentialPairTypeBuilder::lowerDiffPairType(
+IRInst* DifferentialPairTypeBuilder::lowerDiffPairType(
     IRBuilder* builder, IRType* originalPairType)
 {
-    LoweredPairTypeInfo result = {};
-    
+    IRInst* result = nullptr;
     if (pairTypeCache.TryGetValue(originalPairType, result))
         return result;
     auto pairType = as<IRDifferentialPairType>(originalPairType);
     if (!pairType)
     {
-        result.isTrivial = true;
-        result.loweredType = originalPairType;
+        result = originalPairType;
         return result;
     }
     auto primalType = pairType->getValueType();
     if (as<IRParam>(primalType))
     {
-        result.isTrivial = false;
-        result.loweredType = nullptr;
+        result = nullptr;
         return result;
     }
 
     auto diffType = getDiffTypeFromPairType(builder, pairType);
     if (!diffType)
         return result;
-    result.loweredType = _createDiffPairType(pairType->getValueType(), (IRType*)diffType);
-    result.isTrivial = false;
+    result = _createDiffPairType(pairType->getValueType(), (IRType*)diffType);
     pairTypeCache.Add(originalPairType, result);
 
     return result;
@@ -469,6 +474,22 @@ bool processAutodiffCalls(
     // Process reverse derivative calls.
     modified |= processReverseDerivativeCalls(&autodiffContext, sink);
 
+    return modified;
+}
+
+bool finalizeAutoDiffPass(IRModule* module)
+{
+    bool modified = false;
+
+    // Create shared context for all auto-diff related passes
+    AutoDiffSharedContext autodiffContext(module->getModuleInst());
+
+    SharedIRBuilder sharedBuilder;
+    sharedBuilder.init(module);
+    sharedBuilder.deduplicateAndRebuildGlobalNumberingMap();
+
+    autodiffContext.sharedBuilder = &sharedBuilder;
+
     // Replaces IRDifferentialPairType with an auto-generated struct,
     // IRDifferentialPairGetDifferential with 'differential' field access,
     // IRDifferentialPairGetPrimal with 'primal' field access, and
@@ -481,7 +502,7 @@ bool processAutodiffCalls(
     // Remove auto-diff related decorations.
     stripAutoDiffDecorations(module);
 
-    return modified;
+    return false;
 }
 
 
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