# HG changeset patch
# User Tim Deegan <Tim.Deegan@xxxxxxxxxx>
# Date 1299497649 0
# Node ID 9da74925d21627d886dc4d97028149f81bbc50b2
# Parent  d91e6a8d36ad3dbf89f42264334baec0cb37063f
xen: add "lto=y" option to build Xen with link-time optimizations.

This involves gathering object files from .asm (which will be binary)
and object files from .c (which will be in LTO format) separately
until the final link.

Only tested for x86_64 Xen builds using Clang/LLVM bitcode; it should be
possible to do the same with newer GCCs and GIMPLE.

Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>

diff -r d91e6a8d36ad -r 9da74925d216 config/StdGNU.mk
--- a/config/StdGNU.mk	Mon Mar 07 11:21:11 2011 +0000
+++ b/config/StdGNU.mk	Mon Mar 07 11:34:09 2011 +0000
@@ -1,10 +1,11 @@
 AS         = $(CROSS_COMPILE)as
+LD         = $(CROSS_COMPILE)ld
 ifeq ($(clang),y)
-LD         = $(CROSS_COMPILE)gold
 CC         = $(CROSS_COMPILE)clang
+LD_LTO     = $(CROSS_COMPILE)llvm-ld
 else
-LD         = $(CROSS_COMPILE)ld
 CC         = $(CROSS_COMPILE)gcc
+LD_LTO     = $(CROSS_COMPILE)ld
 endif
 CPP        = $(CC) -E
 AR         = $(CROSS_COMPILE)ar
@@ -79,3 +80,10 @@ ifneq ($(clang),y)
 CFLAGS += -fno-optimize-sibling-calls
 endif
 endif
+
+ifeq ($(lto),y)
+CFLAGS += -flto
+ifeq ($(clang),y)
+LDFLAGS += -plugin LLVMgold.so
+endif
+endif
diff -r d91e6a8d36ad -r 9da74925d216 xen/Makefile
--- a/xen/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -159,4 +159,4 @@ FORCE:
 	$(MAKE) -f $(BASEDIR)/Rules.mk -C $(*D) $(@F)
 
 %/: FORCE
-	$(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o
+	$(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o built_in_bin.o
diff -r d91e6a8d36ad -r 9da74925d216 xen/Rules.mk
--- a/xen/Rules.mk	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/Rules.mk	Mon Mar 07 11:34:09 2011 +0000
@@ -9,6 +9,8 @@ perfc_arrays  ?= n
 lock_profile  ?= n
 crash_debug   ?= n
 frame_pointer ?= n
+clang         ?= n
+lto           ?= n
 
 XEN_ROOT=$(BASEDIR)/..
 include $(XEN_ROOT)/Config.mk
@@ -75,7 +77,8 @@ CFLAGS += $(CFLAGS-y)
 
 # Most CFLAGS are safe for assembly files:
 #  -std=gnu{89,99} gets confused by #-prefixed end-of-line comments
-AFLAGS += $(AFLAGS-y) $(filter-out -std=gnu%,$(CFLAGS))
+#  -flto makes no sense and annoys clang
+AFLAGS += $(AFLAGS-y) $(filter-out -std=gnu%,$(filter-out -flto,$(CFLAGS)))
 
 # LDFLAGS are only passed directly to $(LD)
 LDFLAGS += $(LDFLAGS_DIRECT)
@@ -86,18 +89,45 @@ include Makefile
 subdir-n := $(patsubst %,%/,$(patsubst %/,%,$(subdir-n) $(subdir-)))
 subdir-y := $(patsubst %,%/,$(patsubst %/,%,$(subdir-y)))
 
-# Add explicitly declared subdirectories to the object list.
+# Add explicitly declared subdirectories to the object lists.
 obj-y += $(patsubst %/,%/built_in.o,$(subdir-y))
 
-# Add implicitly declared subdirectories (in the object list) to the
+# Add implicitly declared subdirectories (in the object lists) to the
 # subdirectory list, and rewrite the object-list entry.
 subdir-y += $(filter %/,$(obj-y))
 obj-y    := $(patsubst %/,%/built-in.o,$(obj-y))
 
 subdir-all := $(subdir-y) $(subdir-n)
 
+ifeq ($(lto),y)
+# Would like to handle all object files as bitcode, but objects made from
+# pure asm are in a different format and have to be collected separately.
+# Mirror the directory tree, collecting them as built_in_bin.o.
+# If there are no binary objects in a given directory, make a dummy .o
+obj-bin-y += $(patsubst %/built_in.o,%/built_in_bin.o,$(filter %/built_in.o,$(obj-y)))
+else
+# For a non-LTO build, bundle obj-bin targets in with the normal objs.
+obj-y += $(obj-bin-y)
+obj-bin-y :=
+endif
+
 built_in.o: $(obj-y)
+ifeq ($(obj-y),)
+	$(CC) $(CFLAGS) -c -x c /dev/null -o $@
+else
+ifeq ($(lto),y)
+	$(LD_LTO) -r -o $@ $^
+else
 	$(LD) $(LDFLAGS) -r -o $@ $^
+endif
+endif
+
+built_in_bin.o: $(obj-bin-y)
+ifeq ($(obj-bin-y),)
+	$(CC) $(AFLAGS) -c -x assembler /dev/null -o $@
+else
+	$(LD) $(LDFLAGS) -r -o $@ $^
+endif
 
 # Force execution of pattern rules (for which PHONY cannot be directly used).
 .PHONY: FORCE
@@ -106,6 +136,9 @@ FORCE:
 %/built_in.o: FORCE
 	$(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in.o
 
+%/built_in_bin.o: FORCE
+	$(MAKE) -f $(BASEDIR)/Rules.mk -C $* built_in_bin.o
+
 .PHONY: clean
 clean:: $(addprefix _clean_, $(subdir-all))
 	rm -f *.o *~ core $(DEPS)
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/Makefile
--- a/xen/arch/x86/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -10,8 +10,8 @@ subdir-$(x86_64) += x86_64
 
 obj-y += apic.o
 obj-y += bitops.o
-obj-y += clear_page.o
-obj-y += copy_page.o
+obj-bin-y += clear_page.o
+obj-bin-y += copy_page.o
 obj-y += compat.o
 obj-y += debug.o
 obj-y += delay.o
@@ -65,24 +65,38 @@ x86_emulate.o: x86_emulate/x86_emulate.c
 	./boot/mkelf32 $(TARGET)-syms $(TARGET) 0x100000 \
 	`$(NM) -nr $(TARGET)-syms | head -n 1 | sed -e 's/^\([^ ]*\).*/0x\1/'`
 
+
 ALL_OBJS := $(BASEDIR)/arch/x86/boot/built_in.o $(ALL_OBJS)
 
-$(TARGET)-syms: $(ALL_OBJS) xen.lds
+ifeq ($(lto),y)
+# Gather all LTO objects together
+prelink_lto.o: $(ALL_OBJS)
+	$(LD_LTO) -r -o $@ $^
+
+# Link it with all the binary objects
+prelink.o: $(patsubst %/built_in.o,%/built_in_bin.o,$(ALL_OBJS)) prelink_lto.o
+	$(LD) $(LDFLAGS) -r -o $@ $^
+else
+prelink.o: $(ALL_OBJS)
+	$(LD) $(LDFLAGS) -r -o $@ $^
+endif
+
+$(TARGET)-syms: prelink.o xen.lds
 	$(MAKE) -f $(BASEDIR)/Rules.mk $(BASEDIR)/common/symbols-dummy.o
-	$(LD) $(LDFLAGS) -T xen.lds -N $(ALL_OBJS) \
+	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
 	    $(BASEDIR)/common/symbols-dummy.o -o $(@D)/.$(@F).0
 	$(NM) -n $(@D)/.$(@F).0 | $(BASEDIR)/tools/symbols >$(@D)/.$(@F).0.S
 	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).0.o
-	$(LD) $(LDFLAGS) -T xen.lds -N $(ALL_OBJS) \
+	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
 	    $(@D)/.$(@F).0.o -o $(@D)/.$(@F).1
 	$(NM) -n $(@D)/.$(@F).1 | $(BASEDIR)/tools/symbols >$(@D)/.$(@F).1.S
 	$(MAKE) -f $(BASEDIR)/Rules.mk $(@D)/.$(@F).1.o
-	$(LD) $(LDFLAGS) -T xen.lds -N $(ALL_OBJS) \
+	$(LD) $(LDFLAGS) -T xen.lds -N prelink.o \
 	    $(@D)/.$(@F).1.o -o $@
 	rm -f $(@D)/.$(@F).[0-9]*
 
 asm-offsets.s: $(TARGET_SUBARCH)/asm-offsets.c
-	$(CC) $(CFLAGS) -S -o $@ $<
+	$(CC) $(filter-out -flto,$(CFLAGS)) -S -o $@ $<
 
 xen.lds: xen.lds.S
 	$(CC) -P -E -Ui386 $(AFLAGS) -o $@ $<
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/acpi/Makefile
--- a/xen/arch/x86/acpi/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/acpi/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
 subdir-y += cpufreq
 
-obj-y += boot.o
-obj-y += power.o suspend.o wakeup_prot.o cpu_idle.o cpuidle_menu.o
+obj-y += boot.o power.o suspend.o cpu_idle.o cpuidle_menu.o
+obj-bin-y += wakeup_prot.o
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/boot/Makefile
--- a/xen/arch/x86/boot/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/boot/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
-obj-y += head.o
+obj-bin-y += head.o
 
 head.o: reloc.S
 
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/boot/build32.mk
--- a/xen/arch/x86/boot/build32.mk	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/boot/build32.mk	Mon Mar 07 11:34:09 2011 +0000
@@ -6,6 +6,7 @@ include $(XEN_ROOT)/Config.mk
 $(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
 
 CFLAGS += -Werror -fno-builtin -msoft-float
+CFLAGS := $(filter-out -flto,$(CFLAGS)) 
 
 # NB. awk invocation is a portable alternative to 'head -n -1'
 %.S: %.bin
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/hvm/svm/Makefile
--- a/xen/arch/x86/hvm/svm/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/hvm/svm/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,6 +1,6 @@
 obj-y += asid.o
 obj-y += emulate.o
-obj-y += entry.o
+obj-bin-y += entry.o
 obj-y += intr.o
 obj-y += svm.o
 obj-y += vmcb.o
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/hvm/vmx/Makefile
--- a/xen/arch/x86/hvm/vmx/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/hvm/vmx/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
-obj-y += entry.o
+obj-bin-y += entry.o
 obj-y += intr.o
 obj-y += realmode.o
 obj-y += vmcs.o
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/x86_32/Makefile
--- a/xen/arch/x86/x86_32/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/x86_32/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,6 +1,6 @@
 obj-y += domain_page.o
-obj-y += entry.o
-obj-y += gpr_switch.o
+obj-bin-y += entry.o
+obj-bin-y += gpr_switch.o
 obj-y += mm.o
 obj-y += seg_fixup.o
 obj-y += traps.o
@@ -9,4 +9,4 @@ obj-y += pci.o
 
 obj-$(crash_debug) += gdbstub.o
 
-obj-$(supervisor_mode_kernel) += supervisor_mode_kernel.o
+obj-bin-$(supervisor_mode_kernel) += supervisor_mode_kernel.o
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/x86_64/Makefile
--- a/xen/arch/x86/x86_64/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/x86_64/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,7 +1,7 @@
 subdir-y += compat
 
-obj-y += entry.o
-obj-y += gpr_switch.o
+obj-bin-y += entry.o
+obj-bin-y += gpr_switch.o
 obj-y += mm.o
 obj-y += traps.o
 obj-y += machine_kexec.o
@@ -11,7 +11,7 @@ obj-y += mmconf-fam10h.o
 obj-y += mmconfig_64.o
 obj-y += mmconfig-shared.o
 obj-y += compat.o
-obj-y += compat_kexec.o
+obj-bin-y += compat_kexec.o
 obj-y += domain.o
 obj-y += physdev.o
 obj-y += platform_hypercall.o
diff -r d91e6a8d36ad -r 9da74925d216 xen/arch/x86/x86_64/compat/Makefile
--- a/xen/arch/x86/x86_64/compat/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/arch/x86/x86_64/compat/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,2 +1,2 @@
-obj-y += entry.o
+obj-bin-y += entry.o
 
diff -r d91e6a8d36ad -r 9da74925d216 xen/common/libelf/Makefile
--- a/xen/common/libelf/Makefile	Mon Mar 07 11:21:11 2011 +0000
+++ b/xen/common/libelf/Makefile	Mon Mar 07 11:34:09 2011 +0000
@@ -1,4 +1,4 @@
-obj-y := libelf.o
+obj-bin-y := libelf.o
 
 SECTIONS := text data rodata $(foreach n,1 2 4 8,rodata.str1.$(n)) $(foreach r,rel rel.ro,data.$(r) data.$(r).local)