From 88ef80672bf28ab654d11b8ec1c8ec8965ef23fa Mon Sep 17 00:00:00 2001
From: Simon Shillaker <554768+Shillaker@users.noreply.github.com>
Date: Sat, 19 Feb 2022 14:37:06 +0100
Subject: [PATCH] Detect CPU information (#231)

* Add CPU detection

* Tweak script

* Remove unused vars
---
 CMakeLists.txt          |  6 ++----
 cmake/OptimiseCPU.cmake | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 cmake/OptimiseCPU.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1d22398d9..a13f7cd25 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -12,10 +12,8 @@ elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
     add_compile_options(-fcolor-diagnostics)
 endif()
 
-# Assume skylake for some easy performance wins
-if (CMAKE_SYSTEM_PROCESSOR STREQUAL "x86_64")
-    add_compile_options(-march=skylake -mtune=skylake)
-endif ()
+# Optimise for CPU
+include(cmake/OptimiseCPU.cmake)
 
 # Top-level CMake config
 set(CMAKE_CXX_FLAGS "-Wall")
diff --git a/cmake/OptimiseCPU.cmake b/cmake/OptimiseCPU.cmake
new file mode 100644
index 000000000..14bcd96e1
--- /dev/null
+++ b/cmake/OptimiseCPU.cmake
@@ -0,0 +1,41 @@
+set(CPU_VENDOR)
+set(CPU_FAMILY)
+set(CPU_MODEL)
+set(CPU_PROPS)
+
+file(READ "/proc/cpuinfo" _cpuinfo)
+string(REGEX REPLACE ".*vendor_id[ \t]*:[ \t]+([a-zA-Z0-9_-]+).*" "\\1"
+    CPU_VENDOR "${_cpuinfo}")
+string(REGEX REPLACE ".*cpu family[ \t]*:[ \t]+([a-zA-Z0-9_-]+).*" "\\1"
+    CPU_FAMILY "${_cpuinfo}")
+string(REGEX REPLACE ".*model[ \t]*:[ \t]+([a-zA-Z0-9_-]+).*" "\\1"
+    CPU_MODEL "${_cpuinfo}")
+string(REGEX REPLACE ".*flags[ \t]*:[ \t]+([^\n]+).*" "\\1"
+    CPU_PROPS "${_cpuinfo}")
+
+message("Found CPU: Vendor = ${CPU_VENDOR} Family = ${CPU_FAMILY} Model = ${CPU_MODEL} Props = ${CPU_PROPS}")
+
+# See this file for an example of extending this list:
+# https://github.com/VcDevel/Vc/blob/1.4/cmake/OptimizeForArchitecture.cmake
+# See the LLVM source for list of supported arch, e.g. this test:
+# https://github.com/llvm/llvm-project/blob/main/clang/test/Driver/x86-march.c
+
+set(CPU_COMPILE_FLAGS)
+if(CPU_VENDOR STREQUAL "GenuineIntel")
+    if(CPU_FAMILY EQUAL 6)
+        if(CPU_MODEL EQUAL 78 OR CPU_MODEL EQUAL 94)
+            # Skylake
+            set(CPU_COMPILE_FLAGS -march=skylake -mtune=skylake)
+        elseif(CPU_MODEL EQUAL 58 OR CPU_MODEL EQUAL 62)
+            # Ivy bridge
+            set(CPU_COMPILE_FLAGS -march=ivybridge -mtune=ivybridge)
+        endif()
+    endif()
+endif()
+
+if(CPU_COMPILE_FLAGS)
+    message("Setting following CPU-specific compile flags: ${CPU_COMPILE_FLAGS}")
+    add_compile_options(${CPU_COMPILE_FLAGS})
+else()
+    message("Could not provide any CPU-specific compile flags")
+endif()