From 814f63ec32585f281855587fe0a287cee32e4232 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Peter=20K=C3=BCmmel?= Date: Fri, 6 Mar 2015 13:34:06 +0100 Subject: [PATCH] toolchain: add link-time-optimization support MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Add a new option BR2_GCC_ENABLE_LTO that builds gcc and binutils with LTO support. Individual packages still have to enable LTO explicitly by passing '-flto' to GCC, which passes it on to the linker. This option does not add that flag globally. Some packages detect if the compiler supports LTO and enable the flag if it does. To support LTO, ar and ranlib must be called with an argument which triggers the usage of the LTO plugin. Since GCC doesn't call these tools itself, it instead provides wrappers for ar and ranlib that pass the LTO arguments. This way existing Makefiles don't need to be changed for LTO support. However, these wrappers are called -gcc-ar which matches the pattern to link to the buildroot wrapper in the external toolchain logic. So the external toolchain logic is updated to provide the correct symlink. [Thomas: - Add a separate BR2_BINUTILS_ENABLE_LTO option to enable LTO support in binutils. This is a blind option, selected by BR2_GCC_ENABLE_LTO. It just avoids having binutils.mk poke directly into gcc Config.in options. - Remove the check on the AVR32 special gcc version, which we don't support anymore. - Adapt the help text of the LTO Config.in option to no longer mention "Since version 4.5", since we only support gcc >= 4.5 in Buildroot anyway. - Fix typo in toolchain-external.mk comment.] Signed-off-by: Peter Kümmel Signed-off-by: Thomas Petazzoni --- package/binutils/Config.in.host | 3 +++ package/binutils/binutils.mk | 4 ++++ package/gcc/Config.in.host | 7 +++++++ package/gcc/gcc.mk | 4 ++++ toolchain/toolchain-external/toolchain-external.mk | 8 ++++++++ 5 files changed, 26 insertions(+) diff --git a/package/binutils/Config.in.host b/package/binutils/Config.in.host index d0ed84e059..4049cf6a3e 100644 --- a/package/binutils/Config.in.host +++ b/package/binutils/Config.in.host @@ -38,6 +38,9 @@ config BR2_BINUTILS_VERSION default "2.24" if BR2_BINUTILS_VERSION_2_24 default "2.25" if BR2_BINUTILS_VERSION_2_25 +config BR2_BINUTILS_ENABLE_LTO + bool + config BR2_BINUTILS_EXTRA_CONFIG_OPTIONS string "Additional binutils options" default "" diff --git a/package/binutils/binutils.mk b/package/binutils/binutils.mk index 9e992533f3..ac62f1f0d2 100644 --- a/package/binutils/binutils.mk +++ b/package/binutils/binutils.mk @@ -96,5 +96,9 @@ BINUTILS_PRE_PATCH_HOOKS += BINUTILS_XTENSA_PRE_PATCH HOST_BINUTILS_PRE_PATCH_HOOKS += BINUTILS_XTENSA_PRE_PATCH endif +ifeq ($(BR2_BINUTILS_ENABLE_LTO),y) +HOST_BINUTILS_CONF_OPTS += --enable-plugins --enable-lto +endif + $(eval $(autotools-package)) $(eval $(host-autotools-package)) diff --git a/package/gcc/Config.in.host b/package/gcc/Config.in.host index e07d881444..1a5281ca5b 100644 --- a/package/gcc/Config.in.host +++ b/package/gcc/Config.in.host @@ -116,6 +116,13 @@ config BR2_GCC_ENABLE_TLS Enable the compiler to generate code for accessing thread local storage variables +config BR2_GCC_ENABLE_LTO + bool "Enable compiler link-time-optimization support" + select BR2_BINUTILS_ENABLE_LTO + help + This option enables link-time optimization (LTO) support in + gcc. + config BR2_GCC_ENABLE_OPENMP bool "Enable compiler OpenMP support" depends on !BR2_PTHREADS_NONE && !BR2_arc && !BR2_microblaze diff --git a/package/gcc/gcc.mk b/package/gcc/gcc.mk index ffac15c786..b5d2ddba1e 100644 --- a/package/gcc/gcc.mk +++ b/package/gcc/gcc.mk @@ -132,6 +132,10 @@ else HOST_GCC_COMMON_CONF_OPTS += --disable-tls endif +ifeq ($(BR2_GCC_ENABLE_LTO),y) +HOST_GCC_COMMON_CONF_OPTS += --enable-plugins --enable-lto +endif + ifeq ($(BR2_GCC_ENABLE_LIBMUDFLAP),y) HOST_GCC_COMMON_CONF_OPTS += --enable-libmudflap else diff --git a/toolchain/toolchain-external/toolchain-external.mk b/toolchain/toolchain-external/toolchain-external.mk index 78138d370a..612c49d2e1 100644 --- a/toolchain/toolchain-external/toolchain-external.mk +++ b/toolchain/toolchain-external/toolchain-external.mk @@ -647,12 +647,20 @@ endif # Build toolchain wrapper for preprocessor, C and C++ compiler and setup # symlinks for everything else. Skip gdb symlink when we are building our # own gdb to prevent two gdb's in output/host/usr/bin. +# When the link-time-optimazation flag '-flto' is used, then the compiler +# and binutils have to support lto. ar/ranlib need to be called with the +# lto plugin. The wrappers *-gcc-ar and *-gcc-ranlib provided by GCC could +# be used as drop-ins for ar/runlib when Makefiles are used which do not +# pass the lto arguments. define TOOLCHAIN_EXTERNAL_INSTALL_WRAPPER $(Q)$(call MESSAGE,"Building ext-toolchain wrapper") mkdir -p $(HOST_DIR)/usr/bin; cd $(HOST_DIR)/usr/bin; \ for i in $(TOOLCHAIN_EXTERNAL_CROSS)*; do \ base=$${i##*/}; \ case "$$base" in \ + *-ar|*-ranlib|*-nm) \ + ln -sf $$(echo $$i | sed 's%^$(HOST_DIR)%../..%') .; \ + ;; \ *cc|*cc-*|*++|*++-*|*cpp) \ ln -sf ext-toolchain-wrapper $$base; \ ;; \ -- 2.30.2