From 3de17b918d88cfcb91e3d755d317c9bd3e5dba32 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Emmanuel=20Beno=C3=AEt?= <tseeker@nocternity.net>
Date: Fri, 1 Dec 2017 23:08:05 +0100
Subject: [PATCH] Optimizer - Replace constant inputs with constants

---
 c-opopt.cc | 23 +++++++++++++++++------
 c-sync.cc  | 23 +++++++++++++++++++++++
 c-sync.hh  |  7 +++++++
 3 files changed, 47 insertions(+), 6 deletions(-)

diff --git a/c-opopt.cc b/c-opopt.cc
index ef8198c..5d44870 100644
--- a/c-opopt.cc
+++ b/c-opopt.cc
@@ -135,12 +135,23 @@ P_ExpressionNode T_ConstantFolder_::checkExpression(
 
 	// Replace inputs with value if no curve/constant curve
 	if ( node.type( ) == A_Node::EXPR_INPUT ) {
-		// TODO: may be replaced with either a constant or a variable.
-		// * If the curve exists and describes a constant, it's a
-		// constant
-		// * If there is no curve and only one default value in the
-		// whole program then it's also a constant
-		// * No curve, multiple defaults -> variable
+		if ( !curves ) {
+			return {};
+		}
+
+		auto& n{ (T_InputExprNode&) node };
+		auto const* const curve{ 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 {};
 	}
 
diff --git a/c-sync.cc b/c-sync.cc
index f4b9336..818eff4 100644
--- a/c-sync.cc
+++ b/c-sync.cc
@@ -214,6 +214,17 @@ float T_SyncSegment::computeValue(
 	return v * ( values[ part + 1 ] - sv ) + sv;
 }
 
+T_Optional< float > T_SyncSegment::isConstant( ) const noexcept
+{
+	const float f{ values[ 0 ] };
+	for ( auto v : values ) {
+		if ( f != v ) {
+			return {};
+		}
+	}
+	return f;
+}
+
 M_LSHIFT_OP( T_StringBuilder , T_SyncSegment::E_SegmentType )
 {
 	switch ( value ) {
@@ -297,6 +308,18 @@ uint32_t T_SyncCurve::points( ) const noexcept
 	return np;
 }
 
+T_Optional< float > T_SyncCurve::isConstant( ) const noexcept
+{
+	T_Optional< float > v;
+	for ( auto const& s : segments ) {
+		v = s.isConstant( );
+		if ( !v ) {
+			break;
+		}
+	}
+	return v;
+}
+
 
 /*= T_SyncCurves =============================================================*/
 
diff --git a/c-sync.hh b/c-sync.hh
index 59326f7..11ee17e 100644
--- a/c-sync.hh
+++ b/c-sync.hh
@@ -48,6 +48,9 @@ struct T_SyncSegment
 	// Compute the value for the specified position, which is relative
 	// to the start of the segment.
 	float computeValue( float relTimeUnits ) const noexcept;
+
+	// Is the segment constant? If it is, return the value.
+	T_Optional< float > isConstant( ) const noexcept;
 };
 M_LSHIFT_OP( T_StringBuilder , T_SyncSegment::E_SegmentType );
 
@@ -106,6 +109,10 @@ struct T_SyncCurve
 	// inside a segment, or the first and last value in the curve, or
 	// a junction between segments.
 	uint32_t points( ) const noexcept;
+
+	// Does the curve represent a constant? It does if all values in
+	// all segments are identical; in that case the value is returned.
+	T_Optional< float > isConstant( ) const noexcept;
 };
 
 /*----------------------------------------------------------------------------*/