From c0a87ab7907e88efa4a5d7cba27e876f0dab1f5b Mon Sep 17 00:00:00 2001
From: Logan Chien <tzuhsiang.chien@gmail.com>
Date: Tue, 15 Mar 2011 09:13:32 +0800
Subject: Implement copy-when-different build rules for tblgen.

Before this commit, tblgen rules will always generate new file,
change the timestamp, and then a lot of c++ files have to be
recompiled.

This commit modifies transform-td-to-out macro.  Now, tblgen will
generate its output to an intermediate file.  The timestamp of the
inc files will only be changed when the newly generated intermediate
file is different from the old one.
---
 llvm-host-build.mk | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'llvm-host-build.mk')

diff --git a/llvm-host-build.mk b/llvm-host-build.mk
index d7ef682..fe68934 100644
--- a/llvm-host-build.mk
+++ b/llvm-host-build.mk
@@ -63,5 +63,7 @@ $(hide) $(TBLGEN) \
 	-I $(LLVM_ROOT_PATH)/lib/Target	\
 	$(if $(strip $(CLANG_ROOT_PATH)),-I $(CLANG_ROOT_PATH)/include,)	\
 	-gen-$(strip $(1))	\
-	-o $@ $<
+	-o $@.tmp $<
+$(hide) $(LLVM_ROOT_PATH)/copy-diff.py $@.tmp $@
+$(hide) $(RM) $@.tmp
 endef
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