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--- linktimeoptimization [2018/04/07 21:42] – Initial list PaulWebster
+++ linktimeoptimization [2021/10/07 00:25] (current) – Link to build kernel instructions KubilayKocak
@@ Line 1: / Line 1: @@
-A project to build a fully working LTO(lite) %%FreeBSD%% Kernel
+===== Introduction =====
-This is more a log page for progress!
+Link-Time Optimization (LTO) is a compiler toolchain feature that enables additional program optimizations by deferring optimization passes to link time.
-Starting out:
+===== Kernel =====
-* Build and attempt to link a kernel with:
-%%**%% WITHOUT_CTF=yes
+[[https://docs.freebsd.org/en/books/handbook/kernelconfig/#kernelconfig-building|Build and link a kernel]] with:
-%%**%% WITHOUT_DTRACE=yes
-%%**%% sys/conf/kern.mk -flto=thin (for all clang invocations)
+  * WITHOUT_CTF=yes
-%%**%% Try to get it running :)
+  * WITHOUT_DTRACE=yes
+  * sys/conf/kern.mk -flto=thin (for all clang invocations)
+===== Ports =====
+LTO is enabled on LLVM 3.7, but it needs the Gold binutils ld(1) plugin.
+To build with LTO, change your make.conf this way:
+<code>
+CC=/usr/local/bin/clang37
+CXX=/usr/local/bin/clang++37
+CPP=/usr/local/bin/clang-cpp37
+CFLAGS.clang+=-flto
+NM=/usr/local/bin/nm
+NMFLAGS+=--plugin /usr/local/llvm37/lib/LLVMgold.so
+LD=/usr/local/bin/ld.gold
+LDFLAGS+=-fuse-ld=gold -Wl,--plugin /usr/local/llvm37/lib/LLVMgold.so
+</code>
+----
+{{tag>Stale Performance}}