From ae4795261a3eabc99cf0f632c71a4d0d300afc38 Mon Sep 17 00:00:00 2001
From: Chris Kay <chris.kay@arm.com>
Date: Thu, 23 May 2024 13:09:39 +0000
Subject: [PATCH] build(romlib): don't timestamp generated wrappers
The Makefile rule for the libwrappers object files places a dependency
on a timestamp file. This timestamp file is created by the recipe that
generates the libwrappers sources, and was presumably introduced to
indicate to Make that all of the source files are generated
simultaneously by that rule.
Instead, we can use a grouped target rule, which uses `&:` instead of
`:`. This communicates to Make that all of the targets listed are
generated at once.
To demonstrate, the following two Makefile rules differ in their
behaviour:
a.x b.x c.x: # targets may be updated independently
... # generate a.x, b.x and c.x
a.x b.x c.x &: # all targets are updated at once
... # generate a.x, b.x and c.x
While both recipes do generate all three files, only the second rule
communicates this fact to Make. As such, Make can reason that if one of
the files is up to date then all of them are, and avoid re-running the
rule for any generated file that it has not already run it for.
Change-Id: I10b49eb72b5276c7f9bd933900833b03a61cff2f
Signed-off-by: Chris Kay <chris.kay@arm.com>
---
lib/romlib/Makefile | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/lib/romlib/Makefile b/lib/romlib/Makefile
index 438cf839e..da3d3d56d 100644
--- a/lib/romlib/Makefile
+++ b/lib/romlib/Makefile
@@ -84,14 +84,11 @@ $(BUILD_DIR)/jmptbl.i: ../../$(PLAT_DIR)/jmptbl.i
@echo " PRE $@"
$(Q)$(ROMLIB_GEN) pre --output $@ --deps $(BUILD_DIR)/jmptbl.d $<
-$(BUILD_DIR)/wrappers.stamp: $(BUILD_DIR)/jmptbl.i
+$(WRAPPER_SOURCES) &: $(BUILD_DIR)/jmptbl.i
@echo " WRP $<"
$(Q)$(ROMLIB_GEN) genwrappers --bti=$(ENABLE_BTI) -b $(WRAPPER_DIR) $<
- @touch $@
-$(WRAPPER_SOURCES): $(BUILD_DIR)/wrappers.stamp
-
-$(WRAPPER_OBJS): $(WRAPPER_SOURCES) $(BUILD_DIR)/wrappers.stamp
+$(WRAPPER_OBJS): $(WRAPPER_DIR)/%.o: $(WRAPPER_DIR)/%.s
$(BUILD_DIR)/jmptbl.s: $(BUILD_DIR)/jmptbl.i
@echo " TBL $@"