From cff3693387c6d389f83ca25c7a150ae3395a434b Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Fri, 22 Jan 2021 05:50:27 -0800
Subject: Use if constexpr when possible

---
 alc/backends/opensl.cpp | 3 ++-
 alc/backends/wave.cpp   | 3 ++-
 alc/hrtf.cpp            | 4 ++--
 common/albit.h          | 5 +++--
 common/opthelpers.h     | 6 ++++++
 5 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/alc/backends/opensl.cpp b/alc/backends/opensl.cpp
index 926911f0..917e097f 100644
--- a/alc/backends/opensl.cpp
+++ b/alc/backends/opensl.cpp
@@ -37,6 +37,7 @@
 #include "alu.h"
 #include "compat.h"
 #include "core/logging.h"
+#include "opthelpers.h"
 #include "ringbuffer.h"
 #include "threads.h"
 
@@ -104,7 +105,7 @@ constexpr SLuint32 GetTypeRepresentation(DevFmtType type) noexcept
 
 constexpr SLuint32 GetByteOrderEndianness() noexcept
 {
-    if /*constexpr*/(al::endian::native == al::endian::little)
+    if_constexpr(al::endian::native == al::endian::little)
         return SL_BYTEORDER_LITTLEENDIAN;
     return SL_BYTEORDER_BIGENDIAN;
 }
diff --git a/alc/backends/wave.cpp b/alc/backends/wave.cpp
index afff1d56..4f738230 100644
--- a/alc/backends/wave.cpp
+++ b/alc/backends/wave.cpp
@@ -42,6 +42,7 @@
 #include "alu.h"
 #include "compat.h"
 #include "core/logging.h"
+#include "opthelpers.h"
 #include "strutils.h"
 #include "threads.h"
 #include "vector.h"
@@ -149,7 +150,7 @@ int WaveBackend::mixerProc()
             mDevice->renderSamples(mBuffer.data(), mDevice->UpdateSize, frameStep);
             done += mDevice->UpdateSize;
 
-            if /*constexpr*/(al::endian::native != al::endian::little)
+            if_constexpr(al::endian::native != al::endian::little)
             {
                 const uint bytesize{mDevice->bytesFromFmt()};
 
diff --git a/alc/hrtf.cpp b/alc/hrtf.cpp
index 3f4ddf61..60d0aead 100644
--- a/alc/hrtf.cpp
+++ b/alc/hrtf.cpp
@@ -472,7 +472,7 @@ inline T readle(std::istream &data)
     static_assert(num_bits <= sizeof(T)*8, "num_bits is too large for the type");
 
     T ret{};
-    if /*constexpr*/(al::endian::native == al::endian::little)
+    if_constexpr(al::endian::native == al::endian::little)
     {
         if(!data.read(reinterpret_cast<char*>(&ret), num_bits/8))
             return static_cast<T>(EOF);
@@ -485,7 +485,7 @@ inline T readle(std::istream &data)
         std::reverse_copy(std::begin(b), std::end(b), reinterpret_cast<al::byte*>(&ret));
     }
 
-    if /*constexpr*/(std::is_signed<T>::value && num_bits < sizeof(T)*8)
+    if_constexpr(std::is_signed<T>::value && num_bits < sizeof(T)*8)
     {
         constexpr auto signbit = static_cast<T>(1u << (num_bits-1));
         return static_cast<T>((ret^signbit) - signbit);
diff --git a/common/albit.h b/common/albit.h
index c54bb31a..2c83ca08 100644
--- a/common/albit.h
+++ b/common/albit.h
@@ -5,6 +5,7 @@
 #include <type_traits>
 #if !defined(__GNUC__) && (defined(_WIN32) || defined(_WIN64))
 #include <intrin.h>
+#include "opthelpers.h"
 #endif
 
 namespace al {
@@ -104,7 +105,7 @@ inline std::enable_if_t<std::is_integral<T>::value && std::is_unsigned<T>::value
 int> countr_zero(T v)
 {
     unsigned long idx{std::numeric_limits<T>::digits};
-    if /*constexpr*/(std::numeric_limits<T>::digits <= 32)
+    if_constexpr(std::numeric_limits<T>::digits <= 32)
         _BitScanForward(&idx, static_cast<uint32_t>(v));
     else // std::numeric_limits<T>::digits > 32
         _BitScanForward64(&idx, v);
@@ -118,7 +119,7 @@ inline std::enable_if_t<std::is_integral<T>::value && std::is_unsigned<T>::value
 int> countr_zero(T v)
 {
     unsigned long idx{std::numeric_limits<T>::digits};
-    if /*constexpr*/(std::numeric_limits<T>::digits <= 32)
+    if_constexpr(std::numeric_limits<T>::digits <= 32)
         _BitScanForward(&idx, static_cast<uint32_t>(v));
     else if(!_BitScanForward(&idx, static_cast<uint32_t>(v)))
     {
diff --git a/common/opthelpers.h b/common/opthelpers.h
index 8f16fd3f..df0be2f5 100644
--- a/common/opthelpers.h
+++ b/common/opthelpers.h
@@ -36,4 +36,10 @@
 #define ASSUME(x) ((void)0)
 #endif
 
+#if __cplusplus >= 201709L || defined(__cpp_if_constexpr)
+#define if_constexpr if constexpr
+#else
+#define if_constexpr if
+#endif
+
 #endif /* OPTHELPERS_H */
-- 
cgit v1.2.3