[LLVMdev] UPDATE: Makefile.rules Changes / automake update (IMPORTANT!)

[Reid Spencer]

The changes to Makefile.rules have been validated on three platforms
(Linux, Solaris, Darwin) AS LONG AS BUILD_OBJ_DIR != BUILD_SRC_DIR

If you build in the same directory that you check out into, you may
experience some "circular dependency" issues. I'm looking into this now.
In the mean time, just create a FRESH build directory and build there,
separately from your source directory.

Reid.

On Fri, 2004-10-22 at 14:40, Reid Spencer wrote:
> Hello,
> 
> I've closed PR106 (use automake) as WONTFIX. I've already delineated the 
> problems with automake in previous posts but as of now, all the automake 
> related stuff has been removed from the repository.
> 
> In an effort to start making our makefile system better, I've committed changes 
> to Makefile.rules and a few library Makefiles that nearly double the speed of 
> our compilations. I can now build all of LLVM (lib, utils, tools, runtime, 
> examples) in just over 17 minutes on my system. This used to take over 30 
> minutes. There are two main speed ups: (a) we do automatic dependency checking 
> in one pass instead of two, and (b) we use "ar" to archive libraries, not 
> libtool. The first change makes the build generally go faster in all 
> directories. The second change speeds up links slightly because libraries are 
> properly searched for symbols. I have also removed redundant variable 
> definitions and sub-shell invocations (replaced with GNU Make features).
> 
> I have tested these changes quite extensively including the Stacker, sample, 
> llvm-test, Java and reopt projects. If you have another project, you MIGHT be 
> impacted because of a few variable name changes.
> 
> All changes will (soon) be documented in a new "LLVM Makefiles" document that 
> I'll write, but quickly, here's what changed from a USER's perspective:
> 
> * ExtraSource variable became BUILT_SOURCES (standard variable name)
> * SourceDir variable eliminated (redundant with BUILD_SRC_DIR, few uses)
> * Properly allow standard variables to be used (C,CFLAGS,CXX,CXXFLAGS,CPP,
>    CPPFLAGS, LD, LDFLAGS, AR, ARFLAGS, etc) to alter compilation settings on a
>    per directory basis.
> * Build BUILT_SOURCES first (ensures *.td -> *.inc translation occurs)
> * Dependency information is now, by default, generated on every compile. This
>    keeps it constantly up to date. System headers are not tracked so as to
>    reduce make's load time. There is no separate dependency generation pass.
> * Implement auto-reconfiguration (if the configure script changes, you get
>    an automatic reconfiguration instead of a message saying that you need to
>    do so.)
> * Implement auto update of Makefile.config (if you change Makefile.config.in
>    it automatically gets regenerated to Makefile.config)
> * Added tblgen build rules to Makefile.rules and removed from the X86 and
>    PPC target Makefiles. There was some overlap. Standardizing these will
>    encourage future targets to use them. These rules are available if you set
>    the TARGET variable.
> * $(DEST*) variables are gone unless they specifically refer to the
>    installation destination. These conflicted with standard makefile usage
> * $(BUILD_OBJ_DIR)/$(CONFIGURATION) became $(OBJDIR) to simplify it. This is
>    where object files should go.
> * $(LIBDIR) is where libraries should go
> * $(TOOLDIR) is where tools (executables) should go
> * VERBOSE=1 mode is now even quieter (a few rules were missing $(VERB)
> * Build messages have been corrected and made more indicative
> * The "prdirs" target has been replaced with the "printvars" target which
>    prints values for interesting make variables, not just the directories.
> 
> Brian: I've emailed your one Makefile change that you need to use in 
> WholeReoptimizer library after you take the Makefile.rules update.
> 
> Alkis: Some very minor changes were needed in your Java project, but since I 
> don't have access to your cvs repository any more, I can't tell you what 
> changed (my file timestamps are all the same for some reason). So, try building 
> it, if it isn't obvious what's wrong, let me know.
> 
> Misha/Brian: I didn't try compiling LLVM-TV with this, but I doubt you'll run 
> into any significant problems, the user changes are few
> 
> Everyone: llvm-test has successfully compiled and run ONCE with these changes. 
> However, please note that llvm-test no longer depends on llvm/Makefile.rules. I 
> copied the OLD Makefile.rules to llvm-test/Makefile.rules.  The ONLY remaining 
> dependency between llvm-test and llvm proper is the Makefile.confg(.in) file. 
> This was the only "safe/quick" way to ensure I didn't break llvm-test.  As time 
> goes on we need to straighten out the Makefile mess in llvm-test but that's 
> another project.
> 
> Reid.
> 
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