From 4fbcdf61e88f942a85eee5f49aa6550b3dd2a79b Mon Sep 17 00:00:00 2001
From: Reid Spencer <rspencer@reidspencer.com>
Date: Tue, 12 Dec 2006 00:43:38 +0000
Subject: [PATCH] Fix PR1040: Don't rebuild llvm-config if none of the library
 dependencies changed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32455 91177308-0d34-0410-b5e6-96231b3b80d8
---
 tools/llvm-config/Makefile | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/tools/llvm-config/Makefile b/tools/llvm-config/Makefile
index 354723ab2bb..410808b1f26 100644
--- a/tools/llvm-config/Makefile
+++ b/tools/llvm-config/Makefile
@@ -29,11 +29,16 @@ SUB_LDFLAGS =
 
 FinalLibDeps = $(PROJ_OBJ_DIR)/FinalLibDeps.txt
 LibDeps      = $(PROJ_OBJ_DIR)/LibDeps.txt
+LibDepsTemp  = $(PROJ_OBJ_DIR)/LibDeps.txt.tmp
 GenLibDeps   = $(PROJ_SRC_ROOT)/utils/GenLibDeps.pl
 
-$(LibDeps): $(GenLibDeps) $(LibDir) $(wildcard $(LibDir)/*.a $(LibDir)/*.o)
-	$(Echo) "Regenerating LibDeps.txt"
-	$(Verb) $(GenLibDeps) -flat $(LibDir) $(NM_PATH) > $(LibDeps)
+$(LibDepsTemp): $(GenLibDeps) $(LibDir) $(wildcard $(LibDir)/*.a $(LibDir)/*.o)
+	$(Echo) "Regenerating LibDeps.txt.tmp"
+	$(Verb) $(GenLibDeps) -flat $(LibDir) $(NM_PATH) > $(LibDepsTemp)
+
+$(LibDeps): $(LibDepsTemp)
+	$(Verb) $(CMP) -s $@ $< || ( $(CP) $< $@ && \
+	  $(EchoCmd) Updated LibDeps.txt because dependencies changes )
 
 # Find all the cyclic dependencies between various LLVM libraries, so we
 # don't have to process them at runtime.