[PATCH] x86: strip debug info for intermediate linking steps

[Jan Beulich <jbeulich@xxxxxxxx>]

Linking debug info takes time, especially for xen.efi. At the same time
symbol table contents aren't affected by presence / absence of debug info
in the linked binaries (the ELF and COFF symbol tables would have extra
section symbols, but tools/symbols omits those anyway).

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
The main speed gain is from xen.efi linking. Therefore I'm not even sure
if this wants mirroring to the other targets, where only xen-syms is
produced. It would mainly be some transient space saving there. (It would
perhaps want retaining when the linking steps are moved to common code.)
Thoughts?

On the system I measured this on, "real" time went down from 4.9s to 3.9s,
while "user" time went from 7.8s to 6.8s (all approximate values of
course, as there naturally is a bit of variance, and all for full
incremental builds with no other changes, i.e. mainly the final linking
steps getting carried out for the common/version.o change).

--- a/xen/arch/x86/Makefile
+++ b/xen/arch/x86/Makefile
@@ -127,13 +127,13 @@ CFLAGS-$(XEN_BUILD_EFI) += -DXEN_BUILD_E
 $(TARGET)-syms: $(objtree)/prelink.o $(obj)/xen.lds
        $(objtree)/tools/symbols $(all_symbols) --empty > $(dot-target).0.S
        $(MAKE) $(build)=$(@D) $(dot-target).0.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) 
--strip-debug \
              $(dot-target).0.o -o $(dot-target).0
        $(NM) -pa --format=sysv $(dot-target).0 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort \
                > $(dot-target).1.S
        $(MAKE) $(build)=$(@D) $(dot-target).1.o
-       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) \
+       $(LD) $(XEN_LDFLAGS) -T $(obj)/xen.lds $< $(build_id_linker) 
--strip-debug \
            $(dot-target).1.o -o $(dot-target).1
        $(NM) -pa --format=sysv $(dot-target).1 \
                | $(objtree)/tools/symbols $(all_symbols) --sysv --sort 
$(syms-warn-dup-y) \
@@ -205,7 +205,7 @@ endif
        $(MAKE) $(build)=$(@D) .$(@F).0s.o
        $(foreach base, $(VIRT_BASE) $(ALT_BASE), \
                  $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds $< 
$(relocs-dummy) \
-                       $(dot-target).0s.o $(note_file_option) \
+                       $(dot-target).0s.o $(note_file_option) --strip-debug \
                        -o $(dot-target).$(base).0 &&) :
        $(MKRELOC) $(foreach base,$(VIRT_BASE) 
$(ALT_BASE),$(dot-target).$(base).0) \
                > $(dot-target).1r.S
@@ -215,7 +215,7 @@ endif
                > $(dot-target).1s.S
        $(MAKE) $(build)=$(@D) .$(@F).1r.o .$(@F).1s.o
        $(foreach base, $(VIRT_BASE) $(ALT_BASE), \
-                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds $< \
+                 $(LD) $(call EFI_LDFLAGS,$(base)) -T $(obj)/efi.lds $<  
--strip-debug \
                        $(dot-target).1r.o $(dot-target).1s.o 
$(note_file_option) \
                        -o $(dot-target).$(base).1 &&) :
        $(MKRELOC) $(foreach base,$(VIRT_BASE) 
$(ALT_BASE),$(dot-target).$(base).1) \