From ad7462fabd8aa4842d04bd75a6dbaec21387e265 Mon Sep 17 00:00:00 2001
From: stephengold <sgold@sonic.net>
Date: Sat, 1 Feb 2025 15:02:05 -0800
Subject: [PATCH] buildscripts:  add an option to use x86_64 ISA extensions
 with GCC

---
 build.gradle      | 24 +++++++++++++++++++++++-
 gradle.properties |  3 +++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/build.gradle b/build.gradle
index 6ede9a15..9407822f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -136,6 +136,13 @@ model {
                 // always-on CPP defines:
                 cppCompiler.define 'JPH_OBJECT_STREAM'
 
+                // ISA extensions:
+                Boolean use_fma = false
+                if (targetPlatform.architecture.name == 'x86-64' && project.hasProperty('use_fma')) {
+                    use_fma = true
+                    cppCompiler.define 'JPH_USE_AVX2'
+                }
+
                 // buildtype-specific CPP defines:
                 Boolean isDebug = (buildType == buildTypes.Debug)
                 if (isDebug) {
@@ -181,6 +188,17 @@ model {
                     cppCompiler.args '-std=c++17'
                     cppCompiler.args '-Werror=return-type'
 
+                    if (use_fma) {
+                        cppCompiler.args '-msse4.1'
+                        cppCompiler.args '-msse4.2'
+                        cppCompiler.args '-mavx'
+                        cppCompiler.args '-mf16c'
+                        cppCompiler.args '-mavx2'
+                        cppCompiler.args '-mbmi'
+                        cppCompiler.args '-mlzcnt'
+                        cppCompiler.args '-mfma'
+                    }
+
                     if (isDebug) {
                         cppCompiler.args '-O0', '-g3'
                     } else { // buildType == Release
@@ -200,7 +218,11 @@ model {
                 }
 
                 if (buildable) {
-                    println 'Build ' + q + ' using ' + toolChain
+                    if (use_fma) {
+                        println 'Build ' + q + '+FMA using ' + toolChain
+                    } else {
+                        println 'Build ' + q + ' using ' + toolChain
+                    }
 
                     // Generate resource path for native library, one of:
                     //   linux/x86-64/com/github/stephengold/libjoltjni.so
diff --git a/gradle.properties b/gradle.properties
index 09729fa7..944385ab 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -33,6 +33,9 @@ artifact = jolt-jni
 #target = MacOSX_ARM64
 #target = Windows64
 
+## use x86_64 ISA extensions, including AVX2 and FMA (default is to avoid them)
+#use_fma = true
+
 ## additional Java Virtual Machine arguments for the Gradle Daemon
 org.gradle.jvmargs=-Xmx2g