Add support for building subzero with LLVM

Add support for building subzero with LLVM

Since subzero depends on LLVM components, it makes sense to build it
along with the LLVM build. Also, toolchain_build doesn't have support
for a target to depend on another target's working directory. We may want
to fix that in the future, but for now it's simpler to do the build
together with LLVM.

This CL allows subzero to be built from an external directory similar to
the way clang is. However we just use a Make variable directly insetad
of a configure flag to avoid regenerating autoconf files.

R=jvoung@chromium.org, stichnot@chromium.org
BUG=

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-llvm.git;a=commit;h=2b73db4

[Jim Stichnoth, 2014-05-22 16:57:42]

lgtm

https://codereview.chromium.org/299753004/diff/1/Makefile.config.in
File Makefile.config.in (right):

https://codereview.chromium.org/299753004/diff/1/Makefile.config.in#newcode63
Makefile.config.in:63: PROJ_SRC_DIR  := $(patsubst
$(LLVM_SRC_ROOT)/tools/subzero%,$(SUBZERO_SRC_ROOT)%,$(PROJ_SRC_DIR))
Too bad about >80 char line... :(

[jvoung (off chromium), 2014-05-22 19:37:58]

https://codereview.chromium.org/299753004/diff/1/tools/Makefile
File tools/Makefile (right):

https://codereview.chromium.org/299753004/diff/1/tools/Makefile#newcode21
tools/Makefile:21: #ifneq ($(SUBZERO_SRC_ROOT),)
Can remove commented out check?

Seems like the point of the variable (and the check for the similar
CLANG_SRC_ROOT variable) is if you want to configure a different directory name.
E.g., configure --with-clang-srcdir=<other>:

http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20111010/129983.html

Otherwise "OPTIONAL_PARALLEL_DIRS += subzero" could work if you just want to
assume the directory is always called "subzero", and you can remove the variable
too?

[jvoung (off chromium), 2014-05-22 19:41:09]

Okay, I think see -- it's never actually in the directory llvm/tools/subzero --
hence the variable. LGTM

[Derek Schuff, 2014-05-22 23:21:56]

https://codereview.chromium.org/299753004/diff/1/Makefile.config.in
File Makefile.config.in (right):

https://codereview.chromium.org/299753004/diff/1/Makefile.config.in#newcode63
Makefile.config.in:63: PROJ_SRC_DIR  := $(patsubst
$(LLVM_SRC_ROOT)/tools/subzero%,$(SUBZERO_SRC_ROOT)%,$(PROJ_SRC_DIR))
On 2014/05/22 16:57:42, stichnot wrote:
> Too bad about >80 char line... :(

That's a nice line you have there... it would be a shame if it suddenly became
over 80 characters...

https://codereview.chromium.org/299753004/diff/1/tools/Makefile
File tools/Makefile (right):

https://codereview.chromium.org/299753004/diff/1/tools/Makefile#newcode21
tools/Makefile:21: #ifneq ($(SUBZERO_SRC_ROOT),)
On 2014/05/22 19:37:58, jvoung wrote:
> Can remove commented out check?
Removed.
> Seems like the point of the variable (and the check for the similar
> CLANG_SRC_ROOT variable) is if you want to configure a different directory
name.
> E.g., configure --with-clang-srcdir=<other>:

Yes, SUBZERO_SRC_ROOT does not actually exist in llvm/tools but is external. so
it's an absolute path and not just 'subzero'
The Makefile.config.in bit substitutes llvm/tools/subzero with the real path
passed in to Make.

[Derek Schuff, 2014-05-22 23:22:18]

Committed patchset #2 manually as r2b73db4 (presubmit successful).