Improve compile time performance. (#3857)

* Handle type check cache update on extensions more gracefully.

* Correctness fix.

* Cache implcit cast overload resolution results.

* Fix.

* More optimizations.

* Cache implicit default ctor resolution.

* Disable redundancy removal.

* Fix.

* Fix test.

* Fix.

* Correctness fix.

* Fix.

* Fix,

* Fix test.

* Small tweak.

1 files changed, 48 insertions, 0 deletions

diff --git a/source/slang/slang-check-impl.h b/source/slang/slang-check-impl.h
index 569e27e7c..1bb450a6a 100644
--- a/source/slang/slang-check-impl.h
+++ b/source/slang/slang-check-impl.h
@@ -549,6 +549,45 @@ namespace Slang
         FacetList facets;
     };
 
+        /// Cached information about how to convert between two types.
+    struct ImplicitCastMethod
+    {
+        OverloadCandidate conversionFuncOverloadCandidate;
+        ConversionCost cost = kConversionCost_Impossible;
+        bool isAmbiguous = false;
+    };
+
+    struct ImplicitCastMethodKey
+    {
+        Type* fromType; // nullptr means default construct.
+        bool isLValue;
+        Type* toType;
+        uint64_t constantVal;
+        bool isConstant;
+        HashCode getHashCode() const
+        {
+            return combineHash(Slang::getHashCode(fromType), Slang::getHashCode(toType), Slang::getHashCode(constantVal), (HashCode32)isConstant, (HashCode32)isLValue);
+        }
+        bool operator == (const ImplicitCastMethodKey& other) const
+        {
+            return fromType == other.fromType && toType == other.toType && isConstant == other.isConstant && constantVal == other.constantVal && isLValue == other.isLValue;
+        }
+        ImplicitCastMethodKey() = default;
+        ImplicitCastMethodKey(QualType fromType, Type* toType, Expr* fromExpr)
+            : fromType(fromType)
+            , toType(toType)
+            , constantVal(0)
+            , isConstant(false)
+            , isLValue(fromType.isLeftValue)
+        {
+            if (auto constInt = as<IntegerLiteralExpr>(fromExpr))
+            {
+                constantVal = constInt->value;
+                isConstant = true;
+            }
+        }
+    };
+
         /// Shared state for a semantics-checking session.
     struct SharedSemanticsContext
     {
@@ -657,6 +696,14 @@ namespace Slang
             auto pair = TypePair{ sub, sup };
             m_mapTypePairToSubtypeWitness[pair] = outWitness;
         }
+        ImplicitCastMethod* tryGetImplicitCastMethod(ImplicitCastMethodKey key)
+        {
+            return m_mapTypePairToImplicitCastMethod.tryGetValue(key);
+        }
+        void cacheImplicitCastMethod(ImplicitCastMethodKey key, ImplicitCastMethod candidate)
+        {
+            m_mapTypePairToImplicitCastMethod[key] = candidate;
+        }
 
     private:
             /// Mapping from type declarations to the known extensiosn that apply to them
@@ -776,6 +823,7 @@ namespace Slang
         Dictionary<Type*, InheritanceInfo> m_mapTypeToInheritanceInfo;
         Dictionary<DeclRef<Decl>, InheritanceInfo> m_mapDeclRefToInheritanceInfo;
         Dictionary<TypePair, SubtypeWitness*> m_mapTypePairToSubtypeWitness;
+        Dictionary<ImplicitCastMethodKey, ImplicitCastMethod> m_mapTypePairToImplicitCastMethod;
     };
 
         /// Local/scoped state of the semantic-checking system