From 5ef2c9aa09247f9853bf04db0df962fcff764499 Mon Sep 17 00:00:00 2001 From: Matthias Baesken Date: Tue, 25 Nov 2025 08:25:12 +0000 Subject: [PATCH] 8370438: Offer link time optimization support on library level Reviewed-by: erikj, serb, azvegint --- make/autoconf/flags-cflags.m4 | 12 ++++++++++++ make/autoconf/flags-ldflags.m4 | 4 ++++ make/autoconf/spec.gmk.template | 5 +++++ make/common/NativeCompilation.gmk | 1 + make/common/native/Flags.gmk | 9 +++++++++ make/hotspot/lib/CompileJvm.gmk | 1 + make/hotspot/lib/JvmFeatures.gmk | 18 ++++-------------- .../java.desktop/lib/ClientLibraries.gmk | 1 + 8 files changed, 37 insertions(+), 14 deletions(-) diff --git a/make/autoconf/flags-cflags.m4 b/make/autoconf/flags-cflags.m4 index 9d58a280998..6298bcae416 100644 --- a/make/autoconf/flags-cflags.m4 +++ b/make/autoconf/flags-cflags.m4 @@ -282,10 +282,17 @@ AC_DEFUN([FLAGS_SETUP_OPTIMIZATION], C_O_FLAG_DEBUG_JVM="-O0" C_O_FLAG_NONE="-O0" + if test "x$TOOLCHAIN_TYPE" = xgcc; then + C_O_FLAG_LTO="-flto=auto -fuse-linker-plugin -fno-strict-aliasing -fno-fat-lto-objects" + else + C_O_FLAG_LTO="-flto -fno-strict-aliasing" + fi + if test "x$TOOLCHAIN_TYPE" = xclang && test "x$OPENJDK_TARGET_OS" = xaix; then C_O_FLAG_HIGHEST_JVM="${C_O_FLAG_HIGHEST_JVM} -finline-functions" C_O_FLAG_HIGHEST="${C_O_FLAG_HIGHEST} -finline-functions" C_O_FLAG_HI="${C_O_FLAG_HI} -finline-functions" + C_O_FLAG_LTO="${C_O_FLAG_LTO} -ffat-lto-objects" fi # -D_FORTIFY_SOURCE=2 hardening option needs optimization (at least -O1) enabled @@ -317,6 +324,7 @@ AC_DEFUN([FLAGS_SETUP_OPTIMIZATION], C_O_FLAG_DEBUG_JVM="" C_O_FLAG_NONE="-Od" C_O_FLAG_SIZE="-O1" + C_O_FLAG_LTO="-GL" fi # Now copy to C++ flags @@ -328,6 +336,7 @@ AC_DEFUN([FLAGS_SETUP_OPTIMIZATION], CXX_O_FLAG_DEBUG_JVM="$C_O_FLAG_DEBUG_JVM" CXX_O_FLAG_NONE="$C_O_FLAG_NONE" CXX_O_FLAG_SIZE="$C_O_FLAG_SIZE" + CXX_O_FLAG_LTO="$C_O_FLAG_LTO" # Adjust optimization flags according to debug level. case $DEBUG_LEVEL in @@ -360,12 +369,15 @@ AC_DEFUN([FLAGS_SETUP_OPTIMIZATION], AC_SUBST(C_O_FLAG_NORM) AC_SUBST(C_O_FLAG_NONE) AC_SUBST(C_O_FLAG_SIZE) + AC_SUBST(C_O_FLAG_LTO) + AC_SUBST(CXX_O_FLAG_HIGHEST_JVM) AC_SUBST(CXX_O_FLAG_HIGHEST) AC_SUBST(CXX_O_FLAG_HI) AC_SUBST(CXX_O_FLAG_NORM) AC_SUBST(CXX_O_FLAG_NONE) AC_SUBST(CXX_O_FLAG_SIZE) + AC_SUBST(CXX_O_FLAG_LTO) ]) AC_DEFUN([FLAGS_SETUP_CFLAGS], diff --git a/make/autoconf/flags-ldflags.m4 b/make/autoconf/flags-ldflags.m4 index 66f8904db89..ad131b20e27 100644 --- a/make/autoconf/flags-ldflags.m4 +++ b/make/autoconf/flags-ldflags.m4 @@ -61,6 +61,7 @@ AC_DEFUN([FLAGS_SETUP_LDFLAGS_HELPER], fi BASIC_LDFLAGS_JVM_ONLY="" + LDFLAGS_LTO="-flto=auto -fuse-linker-plugin -fno-strict-aliasing" LDFLAGS_CXX_PARTIAL_LINKING="$MACHINE_FLAG -r" @@ -68,6 +69,7 @@ AC_DEFUN([FLAGS_SETUP_LDFLAGS_HELPER], BASIC_LDFLAGS_JVM_ONLY="-mno-omit-leaf-frame-pointer -mstack-alignment=16 \ -fPIC" + LDFLAGS_LTO="-flto=auto -fuse-linker-plugin -fno-strict-aliasing" LDFLAGS_CXX_PARTIAL_LINKING="$MACHINE_FLAG -r" if test "x$OPENJDK_TARGET_OS" = xlinux; then @@ -87,6 +89,7 @@ AC_DEFUN([FLAGS_SETUP_LDFLAGS_HELPER], BASIC_LDFLAGS="-opt:ref" BASIC_LDFLAGS_JDK_ONLY="-incremental:no" BASIC_LDFLAGS_JVM_ONLY="-opt:icf,8 -subsystem:windows" + LDFLAGS_LTO="-LTCG:INCREMENTAL" fi if (test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang) \ @@ -148,6 +151,7 @@ AC_DEFUN([FLAGS_SETUP_LDFLAGS_HELPER], # Export some intermediate variables for compatibility LDFLAGS_CXX_JDK="$DEBUGLEVEL_LDFLAGS_JDK_ONLY" + AC_SUBST(LDFLAGS_LTO) AC_SUBST(LDFLAGS_CXX_JDK) AC_SUBST(LDFLAGS_CXX_PARTIAL_LINKING) ]) diff --git a/make/autoconf/spec.gmk.template b/make/autoconf/spec.gmk.template index 0b336721d65..b3d58704c50 100644 --- a/make/autoconf/spec.gmk.template +++ b/make/autoconf/spec.gmk.template @@ -513,12 +513,14 @@ C_O_FLAG_HI := @C_O_FLAG_HI@ C_O_FLAG_NORM := @C_O_FLAG_NORM@ C_O_FLAG_NONE := @C_O_FLAG_NONE@ C_O_FLAG_SIZE := @C_O_FLAG_SIZE@ +C_O_FLAG_LTO := @C_O_FLAG_LTO@ CXX_O_FLAG_HIGHEST_JVM := @CXX_O_FLAG_HIGHEST_JVM@ CXX_O_FLAG_HIGHEST := @CXX_O_FLAG_HIGHEST@ CXX_O_FLAG_HI := @CXX_O_FLAG_HI@ CXX_O_FLAG_NORM := @CXX_O_FLAG_NORM@ CXX_O_FLAG_NONE := @CXX_O_FLAG_NONE@ CXX_O_FLAG_SIZE := @CXX_O_FLAG_SIZE@ +CXX_O_FLAG_LTO := @CXX_O_FLAG_LTO@ GENDEPS_FLAGS := @GENDEPS_FLAGS@ @@ -587,6 +589,9 @@ LDFLAGS_CXX_JDK := @LDFLAGS_CXX_JDK@ # LDFLAGS specific to partial linking. LDFLAGS_CXX_PARTIAL_LINKING := @LDFLAGS_CXX_PARTIAL_LINKING@ +# LDFLAGS specific to link time optimization +LDFLAGS_LTO := @LDFLAGS_LTO@ + # Sometimes a different linker is needed for c++ libs LDCXX := @LDCXX@ # The flags for linking libstdc++ linker. diff --git a/make/common/NativeCompilation.gmk b/make/common/NativeCompilation.gmk index 9721f1c0aca..28e186adf5f 100644 --- a/make/common/NativeCompilation.gmk +++ b/make/common/NativeCompilation.gmk @@ -98,6 +98,7 @@ include native/Paths.gmk # SYSROOT_CFLAGS the compiler flags for using the specific sysroot # SYSROOT_LDFLAGS the linker flags for using the specific sysroot # OPTIMIZATION sets optimization level to NONE, LOW, HIGH, HIGHEST, HIGHEST_JVM, SIZE +# LINK_TIME_OPTIMIZATION if set to true, enables link time optimization # DISABLED_WARNINGS_ Disable the given warnings for the specified toolchain # DISABLED_WARNINGS__ Disable the given warnings for the specified # toolchain and target OS diff --git a/make/common/native/Flags.gmk b/make/common/native/Flags.gmk index 747e090b816..843701cb4db 100644 --- a/make/common/native/Flags.gmk +++ b/make/common/native/Flags.gmk @@ -194,6 +194,11 @@ define SetupCompilerFlags $1_EXTRA_CXXFLAGS += $(CFLAGS_WARNINGS_ARE_ERRORS) endif + ifeq (true, $$($1_LINK_TIME_OPTIMIZATION)) + $1_EXTRA_CFLAGS += $(C_O_FLAG_LTO) + $1_EXTRA_CXXFLAGS += $(CXX_O_FLAG_LTO) + endif + ifeq (NONE, $$($1_OPTIMIZATION)) $1_OPT_CFLAGS := $(C_O_FLAG_NONE) $1_OPT_CXXFLAGS := $(CXX_O_FLAG_NONE) @@ -222,6 +227,10 @@ define SetupLinkerFlags # Pickup extra OPENJDK_TARGET_OS_TYPE, OPENJDK_TARGET_OS and TOOLCHAIN_TYPE # dependent variables for LDFLAGS and LIBS, and additionally the pair dependent # TOOLCHAIN_TYPE plus OPENJDK_TARGET_OS + ifeq ($$($1_LINK_TIME_OPTIMIZATION), true) + $1_EXTRA_LDFLAGS += $(LDFLAGS_LTO) + endif + $1_EXTRA_LDFLAGS += $$($1_LDFLAGS_$(OPENJDK_TARGET_OS_TYPE)) $$($1_LDFLAGS_$(OPENJDK_TARGET_OS)) \ $$($1_LDFLAGS_$(TOOLCHAIN_TYPE)) $$($1_LDFLAGS_$(TOOLCHAIN_TYPE)_$(OPENJDK_TARGET_OS)) $1_EXTRA_LIBS += $$($1_LIBS_$(OPENJDK_TARGET_OS_TYPE)) $$($1_LIBS_$(OPENJDK_TARGET_OS)) \ diff --git a/make/hotspot/lib/CompileJvm.gmk b/make/hotspot/lib/CompileJvm.gmk index a8b90c92e4d..b0ea27e5081 100644 --- a/make/hotspot/lib/CompileJvm.gmk +++ b/make/hotspot/lib/CompileJvm.gmk @@ -234,6 +234,7 @@ $(eval $(call SetupJdkLibrary, BUILD_LIBJVM, \ LDFLAGS := $(JVM_LDFLAGS), \ LIBS := $(JVM_LIBS), \ OPTIMIZATION := $(JVM_OPTIMIZATION), \ + LINK_TIME_OPTIMIZATION := $(JVM_LTO), \ OBJECT_DIR := $(JVM_OUTPUTDIR)/objs, \ STRIPFLAGS := $(JVM_STRIPFLAGS), \ EMBED_MANIFEST := true, \ diff --git a/make/hotspot/lib/JvmFeatures.gmk b/make/hotspot/lib/JvmFeatures.gmk index 79bbd6a4106..90ea8a985e3 100644 --- a/make/hotspot/lib/JvmFeatures.gmk +++ b/make/hotspot/lib/JvmFeatures.gmk @@ -175,22 +175,12 @@ ifeq ($(call check-jvm-feature, link-time-opt), true) # Set JVM_OPTIMIZATION directly so other jvm-feature flags can override it # later on if desired JVM_OPTIMIZATION := HIGHEST_JVM - ifeq ($(call isCompiler, gcc), true) - JVM_CFLAGS_FEATURES += -flto=auto -fuse-linker-plugin -fno-strict-aliasing \ - -fno-fat-lto-objects - JVM_LDFLAGS_FEATURES += $(CXX_O_FLAG_HIGHEST_JVM) -flto=auto \ - -fuse-linker-plugin -fno-strict-aliasing - else ifeq ($(call isCompiler, clang), true) - JVM_CFLAGS_FEATURES += -flto -fno-strict-aliasing - ifeq ($(call isBuildOs, aix), true) - JVM_CFLAGS_FEATURES += -ffat-lto-objects - endif - JVM_LDFLAGS_FEATURES += $(CXX_O_FLAG_HIGHEST_JVM) -flto -fno-strict-aliasing - else ifeq ($(call isCompiler, microsoft), true) - JVM_CFLAGS_FEATURES += -GL - JVM_LDFLAGS_FEATURES += -LTCG:INCREMENTAL + JVM_LTO := true + ifneq ($(call isCompiler, microsoft), true) + JVM_LDFLAGS_FEATURES += $(CXX_O_FLAG_HIGHEST_JVM) endif else + JVM_LTO := false ifeq ($(call isCompiler, gcc), true) JVM_LDFLAGS_FEATURES += -O1 endif diff --git a/make/modules/java.desktop/lib/ClientLibraries.gmk b/make/modules/java.desktop/lib/ClientLibraries.gmk index 2c29092cdd6..b036973b776 100644 --- a/make/modules/java.desktop/lib/ClientLibraries.gmk +++ b/make/modules/java.desktop/lib/ClientLibraries.gmk @@ -226,6 +226,7 @@ ifeq ($(ENABLE_HEADLESS_ONLY), false) EXCLUDE_FILES := imageioJPEG.c jpegdecoder.c pngtest.c, \ EXCLUDES := $(LIBSPLASHSCREEN_EXCLUDES), \ OPTIMIZATION := SIZE, \ + LINK_TIME_OPTIMIZATION := true, \ CFLAGS := $(LIBSPLASHSCREEN_CFLAGS) \ $(GIFLIB_CFLAGS) $(LIBJPEG_CFLAGS) $(PNG_CFLAGS) $(LIBZ_CFLAGS) \ $(ICONV_CFLAGS), \