From 7162c62d269b80cf8eff0a2c28555e8964bfa78e Mon Sep 17 00:00:00 2001
From: Kfir Itzhak <mastertheknife@gmail.com>
Date: Sat, 25 Mar 2017 21:49:15 +0300
Subject: [PATCH] Implemented a fix to get the Neon code to compile
 successfully with GCC < 6.0

---
 CMakeLists.txt   | 18 ++++++++++++++++++
 src/zm_image.cpp | 18 +++++++++---------
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index baba4218d..dc50358ca 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -66,6 +66,24 @@ set(CMAKE_CXX_FLAGS_DEBUG "-Wall -D__STDC_CONSTANT_MACROS -g")
 set(CMAKE_INCLUDE_CURRENT_DIR ON)
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/Modules/")
 
+# GCC below 6.0 doesn't support __target__("fpu=neon") attribute, required for compiling ARM Neon code, otherwise compilation fails.
+# Must use -mfpu=neon compiler flag instead, but only do that for processors that support neon, otherwise strip the neon code alltogether,
+# because passing -fmpu=neon is unsafe to processors that don't support neon
+IF(CMAKE_SYSTEM_PROCESSOR MATCHES "^arm" AND CMAKE_SYSTEM_NAME MATCHES "Linux")
+	IF(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.0)
+		EXEC_PROGRAM(grep ARGS " neon " "/proc/cpuinfo" OUTPUT_VARIABLE neonoutput RETURN_VALUE neonresult)
+		IF(neonresult EQUAL 0)
+			set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -mfpu=neon")
+			set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -mfpu=neon")
+			set(CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS_DEBUG} -mfpu=neon")
+			set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -mfpu=neon")
+		ELSE(neonresult EQUAL 0)
+			add_definitions(-DZM_STRIP_NEON=1)
+			message(STATUS "ARM Neon is not available on this processor. Neon functions will be absent")
+		ENDIF(neonresult EQUAL 0)
+	ENDIF(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 6.0)
+ENDIF(CMAKE_SYSTEM_PROCESSOR MATCHES "^arm" AND CMAKE_SYSTEM_NAME MATCHES "Linux")
+
 # Modules that we need:
 include (GNUInstallDirs)
 include (CheckIncludeFile)
diff --git a/src/zm_image.cpp b/src/zm_image.cpp
index b65363ae2..63ee58310 100644
--- a/src/zm_image.cpp
+++ b/src/zm_image.cpp
@@ -3291,11 +3291,11 @@ __attribute__((noinline)) void std_fastblend(const uint8_t* col1, const uint8_t*
 }
 
 /* FastBlend Neon for AArch32 */
-#if defined(__arm__)
+#if (defined(__arm__) && !defined(ZM_STRIP_NEON))
 __attribute__((noinline,__target__("fpu=neon")))
 #endif
 void neon32_armv7_fastblend(const uint8_t* col1, const uint8_t* col2, uint8_t* result, unsigned long count, double blendpercent) {
-#if defined(__arm__)
+#if (defined(__arm__) && !defined(ZM_STRIP_NEON))
   static int8_t divider = 0;
   static double current_blendpercent = 0.0;
 
@@ -3348,7 +3348,7 @@ void neon32_armv7_fastblend(const uint8_t* col1, const uint8_t* col2, uint8_t* r
   : "%r12", "%q0", "%q1", "%q2", "%q3", "cc", "memory"
   );
 #else
-  Panic("Neon function called on a non ARM platform");
+  Panic("Neon function called on a non-ARM platform or Neon code is absent");
 #endif
 }
 
@@ -3575,11 +3575,11 @@ __attribute__((noinline)) void std_delta8_abgr(const uint8_t* col1, const uint8_
 }
 
 /* Grayscale Neon for AArch32 */
-#if defined(__arm__)
+#if (defined(__arm__) && !defined(ZM_STRIP_NEON))
 __attribute__((noinline,__target__("fpu=neon")))
 #endif
 void neon32_armv7_delta8_gray8(const uint8_t* col1, const uint8_t* col2, uint8_t* result, unsigned long count) {
-#if defined(__arm__)
+#if (defined(__arm__) && !defined(ZM_STRIP_NEON))
 
   /* Q0(D0,D1) = col1 */
   /* Q1(D2,D3) = col2 */
@@ -3597,16 +3597,16 @@ void neon32_armv7_delta8_gray8(const uint8_t* col1, const uint8_t* col2, uint8_t
   : "%q0", "%q1", "cc", "memory"
   );
 #else
-  Panic("Neon function called on a non ARM platform");
+  Panic("Neon function called on a non-ARM platform or Neon code is absent");
 #endif
 }
 
 /* RGB32 Neon for AArch32 */
-#if defined(__arm__)
+#if (defined(__arm__) && !defined(ZM_STRIP_NEON))
 __attribute__((noinline,__target__("fpu=neon")))
 #endif
 void neon32_armv7_delta8_rgb32(const uint8_t* col1, const uint8_t* col2, uint8_t* result, unsigned long count, uint32_t multiplier) {
-#if defined(__arm__)
+#if (defined(__arm__) && !defined(ZM_STRIP_NEON))
 
   /* Q0(D0,D1) = col1 */
   /* Q1(D2,D3) = col2 */
@@ -3632,7 +3632,7 @@ void neon32_armv7_delta8_rgb32(const uint8_t* col1, const uint8_t* col2, uint8_t
   : "%r12", "%q0", "%q1", "%q2", "cc", "memory"
   );
 #else
-  Panic("Neon function called on a non ARM platform");
+  Panic("Neon function called on a non-ARM platform or Neon code is absent");
 #endif
 }