assigned to @chandlerc

This is because all of LLVM needs to be built PIC to link liblto. We should probably just do this.

-Chris

An --enable-pic option to configure has been added. Chandler is going to try it
out to see if it resolves the problem. The option default to disabled so it
shouldn't affect anyone. When it works, we'll enable it as the default.

Sounds good, when we know it works, we should just enable it by default everywhere. The pain of
building everything multiple times and supporting multiple configurations is far too high to justify
supporting partial pic or any other things. PIC everywhere is goodness :)

Well, the -fPIC option seems to work, but isn't sufficient to solve this
problem. The libs themselves are being linked as static libraries, and can't be
pulled into a shared object. What we need is the split-generation of best static
libs and shared libs so that each can be linked as they are needed (I think?).

As a side note, I feel like when I was using a pure GNU autotools build system
it had an "ok" way of handling this. Ideally, each object is built with -fPIC,
and then two libs are linked, to minimize redundant operations. As a potential
refinement of the -fPIC behavior, as there are small speed gains without it,
perhaps allow building both PIC and non-PIC versions for everything, but only
when optimizations / release builds are enabled. Might allow the halved build
time during development (debugging) builds, but still provide performance gains
in releases, etc. Just a thought.

-Chandler

Ok, I've been setting SHARED_LIBRARY=1 in Makefiles of the various objects that
cause errors when attempting to link LLVMlto, in order to get shared object
versions of those libs. So far, it seems to be removing libraries from the list
of errors, but I hit this snag with LLVMX86:

g++ -shared -nostdlib
/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/../../../../lib64/crti.o
/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/crtbeginS.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86ATTAsmPrinter.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86AsmPrinter.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86CodeEmitter.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86ELFWriter.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86FloatingPoint.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86ISelDAGToDAG.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86ISelLowering.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86InstrInfo.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86IntelAsmPrinter.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86JITInfo.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86RegisterInfo.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86Subtarget.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86TargetAsmInfo.o
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86TargetMachine.o
-L/home/chandlerc/code/compilers/build/llvm/Debug/lib
-L/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1
-L/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/../../../../lib64 -L/lib/../lib64
-L/usr/lib/../lib64
-L/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/../../../../x86_64-pc-linux-gnu/lib
-L/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/../../.. -lstdc++ -lm -lc -lgcc_s
/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/crtendS.o
/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/../../../../lib64/crtn.o -Wl,-soname
-Wl,libLLVMX86.so.0 -o
/home/chandlerc/code/compilers/build/llvm/Debug/lib/.libs/libLLVMX86.so.0.0.0
/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/../../../../x86_64-pc-linux-gnu/bin/ld:
/home/chandlerc/code/compilers/build/llvm/lib/Target/X86/Debug/.libs/X86JITInfo.o:
relocation R_X86_64_PC32 against `X86CompilationCallback2' can not be used when
making a shared object; recompile with -fPIC
/usr/lib/gcc/x86_64-pc-linux-gnu/4.1.1/../../../../x86_64-pc-linux-gnu/bin/ld:
final link failed: Bad value
collect2: ld returned 1 exit status

-Chandler

Patch builds LLVMlto as a static library
This doesn't build LLVMlto in the same manner in linux as it does on darwin.
Getting the build scripts to be able to do this in a reasonable manner (i.e.,
without building every file twice) isn't reasonable at this time. As a
compromise for the short term, we just build it as a static library when not in
Darwin.

Patch to build LLVMlto on non Darwin systems
This is an update to fix a bug that shows up with compilers on other systems.
Particularly, while the library compiles without error, without an (empty)
definition of ~LinkTimeOptimizer(), some compilers (gcc 4.0.3) will throw an
error when linking it into a program.

Reid: can you review the makefile changes please?

-Chris

Makefile changes look fine to me. Much of this was worked out between Chanderl
and I on IRC.

When you have cvs commit access, please apply this Chandler!

Committed patch.