From ffcf2917d507ce0cd71789b6a89b5fb16bb43df0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emmanuel=20Beno=C3=AEt?= <tseeker@nocternity.net>
Date: Sat, 2 Dec 2017 10:40:47 +0100
Subject: [PATCH] Optimizer - Replace curve-less inputs with single default

---
 c-opopt.cc | 81 ++++++++++++++++++++++++++++++++++++++++++------------
 c-opopt.hh | 11 ++++++++
 2 files changed, 74 insertions(+), 18 deletions(-)

diff --git a/c-opopt.cc b/c-opopt.cc
index a995579..e6cecb8 100644
--- a/c-opopt.cc
+++ b/c-opopt.cc
@@ -10,6 +10,31 @@ using namespace opast;
 using namespace opopt;
 
 
+/*= T_OptData ================================================================*/
+
+void T_OptData::findInputDecls(
+		T_OpsParserOutput& program ) noexcept
+{
+	if ( inputDecls ) {
+		return;
+	}
+
+	inputDecls = T_KeyValueTable< T_String , T_Array< T_InputDecl > >{ };
+	visitor.visit( program.root , [this]( A_Node& node , const bool exit ) {
+		if ( exit && node.type( ) == A_Node::OP_INPUT ) {
+			auto& input{ (T_InputInstrNode&) node };
+			auto* da{ inputDecls->get( input.id( ) ) };
+			if ( !da ) {
+				inputDecls->add( input.id( ) , T_Array< T_InputDecl >{ } );
+				da = inputDecls->get( input.id( ) );
+			}
+			da->add( T_InputDecl{ input.location( ) , input.defValue( ) } );
+		}
+		return true;
+	} );
+}
+
+
 /*= CONSTANT FOLDING =========================================================*/
 
 namespace {
@@ -43,6 +68,12 @@ struct T_ConstantFolder_
 	P_ExpressionNode doIdExpr(
 			T_IdentifierExprNode& node ) noexcept;
 
+	// Handle reads from inputs. If there's a curve and it is a constant,
+	// or if there's no curve and only one default value, then the
+	// expression is constant.
+	P_ExpressionNode doInputExpr(
+			T_InputExprNode& node ) noexcept;
+
 	// Transform an unary operator applied to a constant into a constant.
 	P_ExpressionNode doUnaryOp(
 			T_UnaryOperatorNode& node ,
@@ -126,24 +157,7 @@ P_ExpressionNode T_ConstantFolder_::checkExpression(
 
 	// Replace inputs with value if no curve/constant curve
 	if ( node.type( ) == A_Node::EXPR_INPUT ) {
-		if ( !oData.curves ) {
-			return {};
-		}
-
-		auto& n{ (T_InputExprNode&) node };
-		auto const* const curve{ oData.curves->curves.get( n.id( ) ) };
-		if ( curve ) {
-			// Curve present, check if it's constant
-			const auto cval{ curve->isConstant( ) };
-			if ( !cval ) {
-				return {};
-			}
-			return NewOwned< T_ConstantExprNode >( node.parent( ) , *cval );
-		}
-
-		// TODO: check whether there's only one default value; if that's the case,
-		// well, we got ourselves a constant.
-		return {};
+		return doInputExpr( (T_InputExprNode&) node );
 	}
 
 	// Replace UnOp( Cnst ) with result
@@ -180,6 +194,34 @@ P_ExpressionNode T_ConstantFolder_::checkExpression(
 
 /*----------------------------------------------------------------------------*/
 
+P_ExpressionNode T_ConstantFolder_::doInputExpr(
+		T_InputExprNode& node ) noexcept
+{
+	if ( !oData.curves ) {
+		return {};
+	}
+
+	auto const* const curve{ oData.curves->curves.get( node.id( ) ) };
+	if ( curve ) {
+		// Curve present, check if it's constant
+		const auto cval{ curve->isConstant( ) };
+		if ( !cval ) {
+			return {};
+		}
+		return NewOwned< T_ConstantExprNode >( node.parent( ) , *cval );
+	}
+
+	assert( oData.inputDecls );
+	auto const* const dva{ oData.inputDecls->get( node.id( ) ) };
+	assert( dva );
+	if ( dva->size( ) == 1 ) {
+		// If there's only one default value, that's a constant.
+		return NewOwned< T_ConstantExprNode >( node.parent( ) ,
+				(*dva)[ 0 ].value );
+	}
+	return {};
+}
+
 P_ExpressionNode T_ConstantFolder_::doIdExpr(
 		T_IdentifierExprNode& node ) noexcept
 {
@@ -321,6 +363,9 @@ bool opopt::FoldConstants(
 		T_OptData& oData ) noexcept
 {
 	T_ConstantFolder_ folder{ oData };
+	if ( oData.curves ) {
+		oData.findInputDecls( program );
+	}
 	oData.visitor.visit( program.root , folder );
 	return folder.didFold;
 }
diff --git a/c-opopt.hh b/c-opopt.hh
index 2e1a600..d42863e 100644
--- a/c-opopt.hh
+++ b/c-opopt.hh
@@ -23,6 +23,17 @@ struct T_OptData
 
 	// A visitor to be used for the tree
 	ebcl::T_Visitor< opast::A_Node > visitor{ opast::ASTVisitorBrowser };
+
+	// Table of input declarations; used to fold constant inputs.
+	struct T_InputDecl {
+		ebcl::T_SRDLocation location;
+		float value;
+	};
+	T_Optional< T_KeyValueTable< T_String , T_Array< T_InputDecl > > > inputDecls;
+
+	//----------------------------------------------------------------------
+
+	void findInputDecls( T_OpsParserOutput& program ) noexcept;
 };
 
 /*----------------------------------------------------------------------------*/