From 7a7f6f69369a858f9022e44e7f1a8a30bff56c3e Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sun, 26 Aug 2018 21:00:06 +0200
Subject: Remove branch from gray_code_inv

---
 chilbert/detail/MultiBitVec.hpp | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

(limited to 'chilbert')

diff --git a/chilbert/detail/MultiBitVec.hpp b/chilbert/detail/MultiBitVec.hpp
index 283601f..a184287 100644
--- a/chilbert/detail/MultiBitVec.hpp
+++ b/chilbert/detail/MultiBitVec.hpp
@@ -24,6 +24,7 @@
 #include "chilbert/detail/BitVecMask.hpp"
 #include "chilbert/detail/operations.hpp"
 
+#include <array>
 #include <cassert>
 #include <climits>
 #include <cstdint>
@@ -366,15 +367,16 @@ template <class Derived>
 void
 gray_code_inv(MultiBitVec<Derived>& value)
 {
-	typename MultiBitVec<Derived>::Rack s = 0;
+	using Rack = typename MultiBitVec<Derived>::Rack;
+
+	constexpr std::array<Rack, 2> masks{Rack{0}, ~Rack{0}};
+	bool                          s = 0;
 
 	for (size_t ri = 0; ri < value.num_racks(); ++ri) {
 		const size_t i    = value.num_racks() - ri - 1;
 		auto&        rack = value.rack(i);
 		gray_code_inv(rack);
-		if (s) {
-			rack = ~rack;
-		}
+		rack ^= masks[s];
 		s = rack & 1;
 	}
 }
-- 
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