From cdc2b1b5b5e79c667ebb3989f622621f7e829122 Mon Sep 17 00:00:00 2001
From: vng <viktor.govako@gmail.com>
Date: Sat, 4 Sep 2021 23:51:50 +0200
Subject: [PATCH] Added LTO and -Ofast.

Signed-off-by: Viktor Govako <viktor.govako@gmail.com>
---
 CMakeLists.txt                          | 24 +++++++++++++++++++++++-
 geometry/geometry_tests/robust_test.cpp | 10 +++++++++-
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b48a77176..994b486e9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -94,6 +94,11 @@ if (PLATFORM_WIN)
   )
 endif()
 
+# Try fast native arch.
+if (PLATFORM_LINUX)
+  add_compile_options(-march=native)
+endif()
+
 # Built-in CMake configurations: Debug, Release, RelWithDebInfo, MinSizeRel
 if (${CMAKE_BUILD_TYPE} STREQUAL "Debug")
   add_definitions(-DDEBUG)
@@ -103,12 +108,29 @@ if (${CMAKE_BUILD_TYPE} STREQUAL "Debug")
 elseif (${CMAKE_BUILD_TYPE} MATCHES "Rel")
   add_definitions(-DRELEASE)
   if (NOT MSVC)
-    add_compile_options(-Ofast)  # Also enables -ffast-math
+    add_compile_options(-Ofast $<$<CXX_COMPILER_ID:GNU>:-flto=auto>)  # Also enables -ffast-math
   endif()
 else()
   message(FATAL_ERROR "Unknown build type: " ${CMAKE_BUILD_TYPE})
 endif()
 
+if (${CMAKE_BUILD_TYPE} STREQUAL "RelWithDebInfo")
+  add_compile_options(-fno-omit-frame-pointer)
+endif()
+
+# Linux GCC LTO plugin fix.
+if (PLATFORM_LINUX AND (CMAKE_CXX_COMPILER_ID STREQUAL "GNU") AND (CMAKE_BUILD_TYPE MATCHES "^Rel"))
+  # To force errors if LTO was not enabled.
+  add_compile_options(-fno-fat-lto-objects)
+  # To fix ar and ranlib "plugin needed to handle lto object".
+  string(REGEX MATCH "[0-9]+" GCC_MAJOR_VERSION ${CMAKE_CXX_COMPILER_VERSION})
+  file(GLOB_RECURSE plugin /usr/lib/gcc/*/${GCC_MAJOR_VERSION}/liblto_plugin.so)
+  set(CMAKE_C_ARCHIVE_CREATE "<CMAKE_AR> --plugin ${plugin} qcs <TARGET> <OBJECTS>")
+  set(CMAKE_C_ARCHIVE_FINISH "<CMAKE_RANLIB> --plugin ${plugin} <TARGET>")
+  set(CMAKE_CXX_ARCHIVE_CREATE "<CMAKE_AR> --plugin ${plugin} qcs <TARGET> <OBJECTS>")
+  set(CMAKE_CXX_ARCHIVE_FINISH "<CMAKE_RANLIB> --plugin ${plugin} <TARGET>")
+endif()
+
 message(STATUS "Build type: " ${CMAKE_BUILD_TYPE})
 
 if (PLATFORM_LINUX OR PLATFORM_ANDROID)
diff --git a/geometry/geometry_tests/robust_test.cpp b/geometry/geometry_tests/robust_test.cpp
index aaf1db368..b876ba74a 100644
--- a/geometry/geometry_tests/robust_test.cpp
+++ b/geometry/geometry_tests/robust_test.cpp
@@ -62,8 +62,12 @@ UNIT_TEST(Segment_Smoke)
     TEST(!OnSegment(P(10 + eps, 10), ps), ());
     TEST(!OnSegment(P(0, 0), ps), ());
   }
+}
 
-  // Paranoid tests.
+// This paranoid test doesn' work with Release optimizations (LTO?).
+#ifndef NDEBUG
+UNIT_TEST(Segment_Paranoid)
+{
   {
     P ps[] = {{0, 0}, {1e100, 1e100}};
     TEST(OnSegment(ps[0], ps), ());
@@ -94,6 +98,7 @@ UNIT_TEST(Segment_Smoke)
     TEST(!OnSegment(P(1e-16, 2.0 * 1e-16), ps), ());
   }
 }
+#endif
 
 UNIT_TEST(Triangle_Smoke)
 {
@@ -129,6 +134,8 @@ UNIT_TEST(Triangle_PointInsideSegment)
   TEST(!InsideTriangle(P(eps, eps), ps), ());
 }
 
+// This paranoid test doesn' work with Release optimizations (LTO?).
+#ifndef NDEBUG
 UNIT_TEST(Triangle_PointInsidePoint)
 {
   double constexpr eps = 1.0E-10;
@@ -147,6 +154,7 @@ UNIT_TEST(Triangle_PointInsidePoint)
   TEST(!InsideTriangle(P(eps, eps), ps), ());
 #endif
 }
+#endif
 
 UNIT_TEST(PolygonSelfIntersections_IntersectSmoke)
 {