From ee58342a7a37b0d1c483dbcb2f7ffd30e8b1ea61 Mon Sep 17 00:00:00 2001
From: Johannes de Fine Licht <definelicht@inf.ethz.ch>
Date: Tue, 21 Sep 2021 18:27:30 +0200
Subject: [PATCH] Fix ConstLog2

---
 include/hlslib/xilinx/Flatten.h       | 7 ++++---
 include/hlslib/xilinx/ShiftRegister.h | 2 +-
 include/hlslib/xilinx/Utility.h       | 2 +-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/hlslib/xilinx/Flatten.h b/include/hlslib/xilinx/Flatten.h
index c0a1e51..abfe8cb 100644
--- a/include/hlslib/xilinx/Flatten.h
+++ b/include/hlslib/xilinx/Flatten.h
@@ -117,9 +117,10 @@ namespace {
 template <signed long begin, signed long end>
 struct BitsToRepresent {
   static constexpr unsigned kBits =
-      (begin < 0 || end < 0)
-          ? (ConstLog2(hlslib::max(hlslib::abs(begin), hlslib::abs(end))) + 1)
-          : ConstLog2(hlslib::max(begin, end));
+      1 +
+      ((begin < 0 || end < 0)
+           ? (ConstLog2(hlslib::max(hlslib::abs(begin), hlslib::abs(end))) + 1)
+           : ConstLog2(hlslib::max(begin, end)));
   using type = typename std::conditional<(begin < 0 || end < 0), ap_int<kBits>,
                                          ap_uint<kBits>>::type;
 };
diff --git a/include/hlslib/xilinx/ShiftRegister.h b/include/hlslib/xilinx/ShiftRegister.h
index a11e678..0409334 100644
--- a/include/hlslib/xilinx/ShiftRegister.h
+++ b/include/hlslib/xilinx/ShiftRegister.h
@@ -48,7 +48,7 @@ struct _MaxImpl<I, Is...> {
 
 template <typename T, size_t Size>
 class _ShiftRegisterStageImpl {
-  using Index_t = ap_uint<hlslib::ConstLog2(Size)>;
+  using Index_t = ap_uint<hlslib::ConstLog2(Size) + 1>;
 
  public:
   T Shift(T const &next) {
diff --git a/include/hlslib/xilinx/Utility.h b/include/hlslib/xilinx/Utility.h
index f598050..62d91aa 100644
--- a/include/hlslib/xilinx/Utility.h
+++ b/include/hlslib/xilinx/Utility.h
@@ -12,7 +12,7 @@ namespace hlslib {
 // Constexpr methods for compile-time computations
 
 constexpr unsigned char ConstLog2(unsigned long val) {
-  return val == 0 ? 0 : 1 + ConstLog2(val >> 1);
+  return val <= 1 ? 0 : 1 + ConstLog2(val >> 1);
 }
 
 // Integer division with ceil instead of floor