Subzero: Fixes for Hello World and bisection debugging.

Subzero: Fixes for Hello World and bisection debugging.

Add the llvm2ice -sandbox option (false by default) to select between
native and sandboxed code generation.  Currently, it controls whether
the llvm.nacl.read.tp intrinsic is lowered to gs:[0x0] or a call to
__nacl_read_tp.

Change the asm output slightly for -ffunction-sections so that objdump
is more willing to provide a disassembly.

BUG= none
R=jvoung@chromium.org

Committed: https://gerrit.chromium.org/gerrit/gitweb?p=native_client/pnacl-subzero.git;a=commit;h=bfb03e5

[jvoung (off chromium), 2014-08-25 21:01:34]

LGTM

https://codereview.chromium.org/504963002/diff/20001/tests_lit/llvm2ice_tests...
File tests_lit/llvm2ice_tests/nacl-other-intrinsics.ll (right):

https://codereview.chromium.org/504963002/diff/20001/tests_lit/llvm2ice_tests...
tests_lit/llvm2ice_tests/nacl-other-intrinsics.ll:113: ; CHECKO2UREM-LABEL:
test_memcpy
I guess I should have added a CHECKO2REM-LABEL here too, to partition the output
like this.

[Jim Stichnoth, 2014-08-25 21:32:10]

https://codereview.chromium.org/504963002/diff/20001/tests_lit/llvm2ice_tests...
File tests_lit/llvm2ice_tests/nacl-other-intrinsics.ll (right):

https://codereview.chromium.org/504963002/diff/20001/tests_lit/llvm2ice_tests...
tests_lit/llvm2ice_tests/nacl-other-intrinsics.ll:113: ; CHECKO2UREM-LABEL:
test_memcpy
On 2014/08/25 21:01:34, jvoung wrote:
> I guess I should have added a CHECKO2REM-LABEL here too, to partition the
output
> like this.

Ah right, I went ahead and added that.

Also, fixed "O2U" to be the clearer "O2UNSANDBOXED".

[Jim Stichnoth, 2014-08-26 17:29:10]

Committed patchset #3 manually as bfb03e5 (presubmit successful).