diff --git a/internal/shader/shader.go b/internal/shader/shader.go
index da27f4316..365ef636f 100644
--- a/internal/shader/shader.go
+++ b/internal/shader/shader.go
@@ -608,47 +608,7 @@ func (cs *compileState) parseBlock(outer *block, b *ast.BlockStmt, inParams, out
 					return nil, false
 				}
 
-				// TODO: Reduce calls of parseExpr
-
-				var rhsTypes []shaderir.Type
-				for i, e := range l.Lhs {
-					v := variable{
-						name: e.(*ast.Ident).Name,
-					}
-					if len(l.Lhs) == len(l.Rhs) {
-						ts, ok := cs.functionReturnTypes(block, l.Rhs[i])
-						if !ok {
-							_, ts, _, ok = cs.parseExpr(block, l.Rhs[i])
-							if !ok {
-								return nil, false
-							}
-						}
-						if len(ts) > 1 {
-							cs.addError(l.Pos(), fmt.Sprintf("single-value context and multiple-value context cannot be mixed"))
-						}
-						if len(ts) == 1 {
-							v.typ = ts[0]
-						}
-					} else {
-						if i == 0 {
-							var ok bool
-							rhsTypes, ok = cs.functionReturnTypes(block, l.Rhs[0])
-							if !ok {
-								_, rhsTypes, _, ok = cs.parseExpr(block, l.Rhs[0])
-								if !ok {
-									return nil, false
-								}
-							}
-							if len(rhsTypes) != len(l.Lhs) {
-								cs.addError(l.Pos(), fmt.Sprintf("single-value context and multiple-value context cannot be mixed"))
-							}
-						}
-						v.typ = rhsTypes[i]
-					}
-					block.vars = append(block.vars, v)
-				}
-
-				if !cs.assign(block, l.Pos(), l.Lhs, l.Rhs) {
+				if !cs.assign(block, l.Pos(), l.Lhs, l.Rhs, true) {
 					return nil, false
 				}
 			case token.ASSIGN:
@@ -657,7 +617,7 @@ func (cs *compileState) parseBlock(outer *block, b *ast.BlockStmt, inParams, out
 					cs.addError(l.Pos(), fmt.Sprintf("single-value context and multiple-value context cannot be mixed"))
 					return nil, false
 				}
-				if !cs.assign(block, l.Pos(), l.Lhs, l.Rhs) {
+				if !cs.assign(block, l.Pos(), l.Lhs, l.Rhs, false) {
 					return nil, false
 				}
 			case token.ADD_ASSIGN, token.SUB_ASSIGN, token.MUL_ASSIGN, token.QUO_ASSIGN, token.REM_ASSIGN:
@@ -768,21 +728,43 @@ func (cs *compileState) parseBlock(outer *block, b *ast.BlockStmt, inParams, out
 	return block, true
 }
 
-func (cs *compileState) assign(block *block, pos token.Pos, lhs, rhs []ast.Expr) bool {
+func (cs *compileState) assign(block *block, pos token.Pos, lhs, rhs []ast.Expr, define bool) bool {
 	var rhsExprs []shaderir.Expr
-	for i := range lhs {
+	var rhsTypes []shaderir.Type
+
+	for i, e := range lhs {
 		// Prase RHS first for the order of the statements.
 		if len(lhs) == len(rhs) {
-			rhs, _, stmts, ok := cs.parseExpr(block, rhs[i])
+			r, origts, stmts, ok := cs.parseExpr(block, rhs[i])
 			if !ok {
 				return false
 			}
-			if len(rhs) > 1 {
-				cs.addError(pos, fmt.Sprintf("single-value context and multiple-value context cannot be mixed"))
-			}
 			block.ir.Stmts = append(block.ir.Stmts, stmts...)
 
-			lhs, _, stmts, ok := cs.parseExpr(block, lhs[i])
+			if define {
+				v := variable{
+					name: e.(*ast.Ident).Name,
+				}
+				ts, ok := cs.functionReturnTypes(block, rhs[i])
+				if !ok {
+					ts = origts
+				}
+				if len(ts) > 1 {
+					cs.addError(pos, fmt.Sprintf("single-value context and multiple-value context cannot be mixed"))
+					return false
+				}
+				if len(ts) == 1 {
+					v.typ = ts[0]
+				}
+				block.vars = append(block.vars, v)
+			}
+
+			if len(r) > 1 {
+				cs.addError(pos, fmt.Sprintf("single-value context and multiple-value context cannot be mixed"))
+				return false
+			}
+
+			l, _, stmts, ok := cs.parseExpr(block, lhs[i])
 			if !ok {
 				return false
 			}
@@ -790,13 +772,13 @@ func (cs *compileState) assign(block *block, pos token.Pos, lhs, rhs []ast.Expr)
 
 			block.ir.Stmts = append(block.ir.Stmts, shaderir.Stmt{
 				Type:  shaderir.Assign,
-				Exprs: []shaderir.Expr{lhs[0], rhs[0]},
+				Exprs: []shaderir.Expr{l[0], r[0]},
 			})
 		} else {
 			if i == 0 {
 				var stmts []shaderir.Stmt
 				var ok bool
-				rhsExprs, _, stmts, ok = cs.parseExpr(block, rhs[0])
+				rhsExprs, rhsTypes, stmts, ok = cs.parseExpr(block, rhs[0])
 				if !ok {
 					return false
 				}
@@ -806,7 +788,15 @@ func (cs *compileState) assign(block *block, pos token.Pos, lhs, rhs []ast.Expr)
 				block.ir.Stmts = append(block.ir.Stmts, stmts...)
 			}
 
-			lhs, _, stmts, ok := cs.parseExpr(block, lhs[i])
+			if define {
+				v := variable{
+					name: e.(*ast.Ident).Name,
+				}
+				v.typ = rhsTypes[i]
+				block.vars = append(block.vars, v)
+			}
+
+			l, _, stmts, ok := cs.parseExpr(block, lhs[i])
 			if !ok {
 				return false
 			}
@@ -814,7 +804,7 @@ func (cs *compileState) assign(block *block, pos token.Pos, lhs, rhs []ast.Expr)
 
 			block.ir.Stmts = append(block.ir.Stmts, shaderir.Stmt{
 				Type:  shaderir.Assign,
-				Exprs: []shaderir.Expr{lhs[0], rhsExprs[i]},
+				Exprs: []shaderir.Expr{l[0], rhsExprs[i]},
 			})
 		}
 	}
diff --git a/internal/shader/testdata/define2.expected.vs b/internal/shader/testdata/define2.expected.vs
index 4fb5c8e2a..e1f67f63a 100644
--- a/internal/shader/testdata/define2.expected.vs
+++ b/internal/shader/testdata/define2.expected.vs
@@ -3,12 +3,10 @@ void F0(out vec2 l0) {
 	vec2 l2 = vec2(0);
 	vec2 l3 = vec2(0);
 	vec2 l4 = vec2(0);
-	vec2 l5 = vec2(0);
-	vec2 l6 = vec2(0);
+	F1(l1);
+	l2 = (1.0) * (l1);
 	F1(l3);
-	l2 = (1.0) * (l3);
-	F1(l6);
-	l5 = (l6) * (1.0);
+	l4 = (l3) * (1.0);
 	l0 = l2;
 	return;
 }
diff --git a/internal/shader/testdata/define_multiple.expected.vs b/internal/shader/testdata/define_multiple.expected.vs
index dfeb5c92b..6676720bb 100644
--- a/internal/shader/testdata/define_multiple.expected.vs
+++ b/internal/shader/testdata/define_multiple.expected.vs
@@ -3,10 +3,10 @@ void F0(in vec2 l0, out vec4 l1) {
 	float l3 = float(0);
 	float l4 = float(0);
 	float l5 = float(0);
-	F1(l4, l5);
-	l2 = l4;
-	l3 = l5;
-	l1 = vec4(l0, l2, l2);
+	F1(l2, l3);
+	l4 = l2;
+	l5 = l3;
+	l1 = vec4(l0, l4, l4);
 	return;
 }