From 3cad81afdb7b2fe7e7f26deda4a8848dbef9c6e6 Mon Sep 17 00:00:00 2001
From: Simon Shillaker <554768+Shillaker@users.noreply.github.com>
Date: Mon, 14 Mar 2022 14:59:08 +0100
Subject: [PATCH] Add flag for optimising for specific CPU (#240)

---
 CMakeLists.txt          |  9 ++++++++-
 cmake/OptimiseCPU.cmake | 41 -----------------------------------------
 tasks/dev.py            |  9 ++++++++-
 3 files changed, 16 insertions(+), 43 deletions(-)
 delete mode 100644 cmake/OptimiseCPU.cmake

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a13f7cd25..13d549c94 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,6 +5,8 @@ option(FAABRIC_WASM_BUILD "Build Faabric wasm library" OFF)
 option(FAABRIC_BUILD_TESTS "Build Faabric tests" ON)
 option(FAABRIC_SELF_TRACING "Turn on system tracing using the logger" OFF)
 
+option(FAABRIC_TARGET_CPU "CPU to optimise for, e.g. skylake, icelake or native" OFF)
+
 # Enable colorized compiler output
 if("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
     add_compile_options(-fdiagnostics-color=always)
@@ -13,7 +15,12 @@ elseif("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
 endif()
 
 # Optimise for CPU
-include(cmake/OptimiseCPU.cmake)
+if(FAABRIC_TARGET_CPU)
+    message(STATUS "Optimising Faabric for CPU ${FAABRIC_TARGET_CPU}")
+    add_compile_options(-march=${FAABRIC_TARGET_CPU} -mtune=${FAABRIC_TARGET_CPU})
+else()
+    message(STATUS "Faabric not optimised for specific CPU")
+endif()
 
 # Top-level CMake config
 set(CMAKE_CXX_FLAGS "-Wall")
diff --git a/cmake/OptimiseCPU.cmake b/cmake/OptimiseCPU.cmake
deleted file mode 100644
index 14bcd96e1..000000000
--- a/cmake/OptimiseCPU.cmake
+++ /dev/null
@@ -1,41 +0,0 @@
-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()
diff --git a/tasks/dev.py b/tasks/dev.py
index 3559e1f1b..023c773ac 100644
--- a/tasks/dev.py
+++ b/tasks/dev.py
@@ -15,7 +15,13 @@
 
 @task
 def cmake(
-    ctx, clean=False, shared=False, build="Debug", sanitiser="None", prof=False
+    ctx,
+    clean=False,
+    shared=False,
+    build="Debug",
+    sanitiser="None",
+    prof=False,
+    cpu=None,
 ):
     """
     Configures the build
@@ -44,6 +50,7 @@ def cmake(
         "-DCMAKE_C_COMPILER=/usr/bin/clang-13",
         "-DFAABRIC_USE_SANITISER={}".format(sanitiser),
         "-DFAABRIC_SELF_TRACING=ON" if prof else "",
+        "-DFAABRIC_TARGET_CPU={}".format(cpu) if cpu else "",
         PROJ_ROOT,
     ]