build: use thin archives rather than incremental linking

This changes to build system to use thin archives rather than
incremental linking for built-in.o, similar to recent change to Linux.
built-in.o is renamed to built-in.a, and is created as a thin archive
with no index, for speed and size. All built-in.a are aggregated into
a skiboot.tmp.a which is a thin archive built with an index, making it
suitable or linking. This is input into the final link.

The advantags of build size and linker code placement flexibility are
not as great with skiboot as a bigger project like Linux, but it's a
conceptually better way to build, and is more compatible with link
time optimisation in toolchains which might be interesting for skiboot
particularly for size reductions.

Size of build tree before this patch is 34.4MB, afterwards 23.1MB.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

6 files changed, 6 insertions, 6 deletions

diff --git a/platforms/Makefile.inc b/platforms/Makefile.inc
index 90cd0f1..3269532 100644
--- a/platforms/Makefile.inc
+++ b/platforms/Makefile.inc
@@ -1,7 +1,7 @@
 PLATDIR = platforms
 
 SUBDIRS += $(PLATDIR)
-PLATFORMS = $(PLATDIR)/built-in.o
+PLATFORMS = $(PLATDIR)/built-in.a
 
 include $(SRC)/$(PLATDIR)/ibm-fsp/Makefile.inc
 include $(SRC)/$(PLATDIR)/rhesus/Makefile.inc
diff --git a/platforms/astbmc/Makefile.inc b/platforms/astbmc/Makefile.inc
index 49292c1..d996536 100644
--- a/platforms/astbmc/Makefile.inc
+++ b/platforms/astbmc/Makefile.inc
@@ -6,6 +6,6 @@ ASTBMC_OBJS = pnor.o common.o slots.o \
 	      garrison.o barreleye.o \
 	      witherspoon.o zaius.o romulus.o p9dsu.o
 
-ASTBMC = $(PLATDIR)/astbmc/built-in.o
+ASTBMC = $(PLATDIR)/astbmc/built-in.a
 $(ASTBMC): $(ASTBMC_OBJS:%=$(PLATDIR)/astbmc/%)
 
diff --git a/platforms/ibm-fsp/Makefile.inc b/platforms/ibm-fsp/Makefile.inc
index e9daab2..c4b55a3 100644
--- a/platforms/ibm-fsp/Makefile.inc
+++ b/platforms/ibm-fsp/Makefile.inc
@@ -2,6 +2,6 @@ SUBDIRS += $(PLATDIR)/ibm-fsp
 
 IBM_FSP_OBJS = common.o lxvpd.o apollo.o apollo-pci.o \
 	       firenze.o firenze-pci.o zz.o
-IBM_FSP = $(PLATDIR)/ibm-fsp/built-in.o
+IBM_FSP = $(PLATDIR)/ibm-fsp/built-in.a
 $(IBM_FSP): $(IBM_FSP_OBJS:%=$(PLATDIR)/ibm-fsp/%)
 
diff --git a/platforms/mambo/Makefile.inc b/platforms/mambo/Makefile.inc
index f3023ef..b0e6b0c 100644
--- a/platforms/mambo/Makefile.inc
+++ b/platforms/mambo/Makefile.inc
@@ -1,6 +1,6 @@
 SUBDIRS += $(PLATDIR)/mambo
 
 MAMBO_OBJS = mambo.o console.o
-MAMBO = $(PLATDIR)/mambo/built-in.o
+MAMBO = $(PLATDIR)/mambo/built-in.a
 $(MAMBO): $(MAMBO_OBJS:%=$(PLATDIR)/mambo/%)
 
diff --git a/platforms/qemu/Makefile.inc b/platforms/qemu/Makefile.inc
index 11a44db..d4f988e 100644
--- a/platforms/qemu/Makefile.inc
+++ b/platforms/qemu/Makefile.inc
@@ -1,6 +1,6 @@
 SUBDIRS += $(PLATDIR)/qemu
 
 QEMU_OBJS = qemu.o
-QEMU = $(PLATDIR)/qemu/built-in.o
+QEMU = $(PLATDIR)/qemu/built-in.a
 $(QEMU): $(QEMU_OBJS:%=$(PLATDIR)/qemu/%)
 
diff --git a/platforms/rhesus/Makefile.inc b/platforms/rhesus/Makefile.inc
index 5899ca2..3a3fd87 100644
--- a/platforms/rhesus/Makefile.inc
+++ b/platforms/rhesus/Makefile.inc
@@ -1,6 +1,6 @@
 SUBDIRS += $(PLATDIR)/rhesus
 
 RHESUS_OBJS = rhesus.o
-RHESUS = $(PLATDIR)/rhesus/built-in.o
+RHESUS = $(PLATDIR)/rhesus/built-in.a
 $(RHESUS): $(RHESUS_OBJS:%=$(PLATDIR)/rhesus/%)