From b513d0deef521318ad943d820dd37029075a33c4 Mon Sep 17 00:00:00 2001
From: Sai Praveen Bangaru <31557731+saipraveenb25@users.noreply.github.com>
Date: Mon, 11 Jul 2022 23:18:06 -0400
Subject: Added support for differentiating calls to basic functions, as well
 as arithmetic on the float3 type (#2313)

* Added support for differentiating calls to basic functions, as well as arithmetic on the float3 type

* Added test expected result
---
 source/slang/slang-check-expr.cpp | 37 ++++++++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 11 deletions(-)

(limited to 'source/slang/slang-check-expr.cpp')

diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index df58b11ed..a3fec4802 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -1509,6 +1509,29 @@ namespace Slang
         return expr;
     }
 
+    Type* primalToJVPParamType(ASTBuilder* builder, Type* primalType)
+    {
+        // Only float and float3 types can be differentiated for now.
+        
+        if(primalType->equals(builder->getFloatType()))
+            return primalType;
+        else if(auto primalVectorType = as<VectorExpressionType>(primalType))
+        {
+            // TODO(sai): There's probably a more elegant way to check if a type is a float3?
+            if (getIntVal(primalVectorType->elementCount) == 3 && primalVectorType->elementType->equals(builder->getFloatType()))
+                return primalVectorType;
+        }
+        return nullptr;
+    }
+
+    Type* primalToJVPReturnType(ASTBuilder* builder, Type* primalType)
+    {
+        if(auto jvpType = primalToJVPParamType(builder, primalType))
+            return jvpType;
+        else
+            return builder->getVoidType();
+    }
+
     Expr* SemanticsExprVisitor::visitJVPDifferentiateExpr(JVPDifferentiateExpr* expr)
     {
         // Check/Resolve inner function declaration.
@@ -1524,18 +1547,10 @@ namespace Slang
             
             FuncType* jvpType = astBuilder->create<FuncType>();
 
-            // Only float types can be differentiated for now.
-
             // The JVP return type is float if primal return type is float
             // void otherwise.
             //
-            if (primalType->resultType->equals(astBuilder->getFloatType()))
-                jvpType->resultType = astBuilder->getFloatType();
-            else
-            {
-                //TODO(yong): issue proper diagnostic here.
-                jvpType->resultType = astBuilder->getVoidType();
-            }
+            jvpType->resultType = primalToJVPReturnType(astBuilder, primalType->getResultType());
             
             // No support for differentiating function that throw errors, for now.
             SLANG_ASSERT(primalType->errorType->equals(astBuilder->getBottomType()));
@@ -1548,8 +1563,8 @@ namespace Slang
 
             for (UInt i = 0; i < primalType->getParamCount(); i++)
             {
-                if(primalType->getParamType(i)->equals(astBuilder->getFloatType()))
-                    jvpType->paramTypes.add(astBuilder->getFloatType());
+                if(auto jvpParamType = primalToJVPParamType(astBuilder, primalType->getParamType(i)))
+                    jvpType->paramTypes.add(jvpParamType);
             }
 
             expr->type = jvpType;
-- 
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