The original libFuzzer Fuchsia port relied on convenience libraries,
but these are not exported as part of Fuchsia sysroot. This change
eliminates the use of these libraries and relies on public API only.
Differential Revision: https://reviews.llvm.org/D42996
llvm-svn: 324454
Summary:
Before Xcode 4.5, undefined weak symbols don't work reliably on Darwin:
https://stackoverflow.com/questions/6009321/weak-symbol-link-on-mac-os-x
Therefore this patch disables their use before Mac OS X 10.9 which is the first version
only supported by Xcode 4.5 and above.
Reviewers: glider, kcc, vitalybuka
Reviewed By: vitalybuka
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D41346
llvm-svn: 324284
Summary:
The 32-bit division breaks SizeClassAllocator64PopulateFreeListOOM which uses
Primary that has a maximum size > 32-bit.
Reviewers: alekseyshl
Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42928
llvm-svn: 324268
Summary:
In `ClassID`, make sure we use an unsigned as based for the `lbits` shift.
The previous code resulted in spurious sign extensions like for x64:
```
add esi, 0FFFFFFFFh
movsxd rcx, esi
and rcx, r15
```
The code with the `U` added is:
```
add esi, 0FFFFFFFFh
and rsi, r15
```
And for `MaxCachedHint`, use a 32-bit division instead of `64-bit`, which is
faster (https://lemire.me/blog/2017/11/16/fast-exact-integer-divisions-using-floating-point-operations/)
and already used in other parts of the code (64-bit `GetChunkIdx`, 32-bit
`GetMetaData` enforce 32-bit divisions)
Not major performance gains by any mean, but they don't hurt.
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: kubamracek, delcypher, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D42916
llvm-svn: 324263
Summary:
Here are a few improvements proposed for the local cache:
- `InitCache` always read from `per_class_[1]` in the fast path. This was not
ideal as we are working with `per_class_[class_id]`. The latter offers the
same property we are looking for (eg: `max_count != 0` means initialized),
so we might as well use it and keep our memory accesses local to the same
`per_class_` element. So change `InitCache` to take the current `PerClass`
as an argument. This also makes the fast-path assembly of `Deallocate` a lot
more compact;
- Change the 32-bit `Refill` & `Drain` functions to mimic their 64-bit
counterparts, by passing the current `PerClass` as an argument. This saves
some array computations;
- As far as I can tell, `InitCache` has no place in `Drain`: it's either called
from `Deallocate` which calls `InitCache`, or from the "upper" `Drain` which
checks for `c->count` to be greater than 0 (strictly). So remove it there.
- Move the `stats_` updates to after we are done with the `per_class_` accesses
in an attempt to preserve locality once more;
- Change some `CHECK` to `DCHECK`: I don't think the ones changed belonged in
the fast path and seemed to be overly cautious failsafes;
- Mark some variables as `const`.
The overall result is cleaner more compact fast path generated code, and some
performance gains with Scudo (and likely other Sanitizers).
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: kubamracek, delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42851
llvm-svn: 324257
The "sleep(5)" sometimes times out on our bots, causing the test to fail. Let's use pthread_join.
Differential Revision: https://reviews.llvm.org/D42862
llvm-svn: 324126
Late fix for SVN r. 324034
Add new interceptors: strlcpy(3) and strlcat(3)
There was forgotten an addition of len to the return value.
llvm-svn: 324091
Summary:
Implement `MonotonicNanoTime` using `QueryPerformanceCounter`.
This function is used by Scudo & the 64-bit Primary allocator. Implementing it
now means that the release-to-OS mechanism of the Primary will kick in (it
never did since the function returned 0 always), but `ReleaseMemoryPagesToOS` is
still not currently implemented for Windows.
Performance wise, this adds a syscall & a 64-bit division per call to
`MonotonicNanoTime` so the impact might not be negligible, but I don't think
there is a way around it.
Reviewers: rnk, alekseyshl, amccarth
Reviewed By: alekseyshl, amccarth
Subscribers: amccarth, flowerhack, kubamracek, delcypher, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D42579
llvm-svn: 324011
Summary:
Few changes to the secondary:
- mark `const` variables as such;
- change some `CHECK` to `DCHECK`: I don't feel we need to be as conservative as
we were with out checks, as they are the results of our own computation.
- mark a condition as `UNLIKELY`.
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42696
llvm-svn: 323997
Summary:
With the change, one can choose not to report comparison (or subtraction)
of a pointer with nullptr pointer.
Reviewers: kcc, jakubjelinek, alekseyshl
Reviewed By: alekseyshl
Subscribers: kubamracek
Differential Revision: https://reviews.llvm.org/D41479
llvm-svn: 323995
This avoids the warnings when building with LLVM_ENABLE_LIBCXX
which automatically adds -stdlib=libc++ to CMAKE_CXX_FLAGS.
Differential Revision: https://reviews.llvm.org/D42238
llvm-svn: 323969
Summary:
This change expands the amount of registers stashed by the entry and
`__xray_CustomEvent` trampolines.
We've found that since the `__xray_CustomEvent` trampoline calls can show up in
situations where the scratch registers are being used, and since we don't
typically want to affect the code-gen around the disabled
`__xray_customevent(...)` intrinsic calls, that we need to save and restore the
state of even the scratch registers in the handling of these custom events.
Reviewers: pcc, pelikan, dblaikie, eizan, kpw, echristo, chandlerc
Reviewed By: echristo
Subscribers: chandlerc, echristo, hiraditya, davide, dblaikie, llvm-commits
Differential Revision: https://reviews.llvm.org/D40894
llvm-svn: 323940
This change updates the Fuchsia-specific code to use the C++ friendly
duration expressions and flips on the building of
libclang_rt.fuzzer-x86_64.a and similar for Fuchsia. Given that
compiler-rt doesn't build on Fuchsia, test have been run by explicitly
building the library and linking it against
lib/fuzzer/tests/FuzzerUnittest.cpp.
Differential Revision: https://reviews.llvm.org/D42670
llvm-svn: 323828
Summary:
This is in preparation for platforms where `SANITIZER_SUPPORTS_WEAK_HOOKS` is 0.
They require a default implementation.
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: delcypher, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D42557
llvm-svn: 323795
Summary:
Turns out sizeof(packed) isn't as strong as we'd hoped. This makes sure
that when we initialize the padding, all 12 bytes will be zero.
Reviewers: dberris, kpw, eizan
Subscribers: delcypher, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D42494
llvm-svn: 323755
There was a failure on a bot:
http://lab.llvm.org:8011/builders/clang-cmake-mipsel/builds/1283
strerror test is indeed flaky. We protect all races by a barrier in other tests
to eliminate flakiness. Do the same here.
No idea why tls_race2.cc failed. Add output at the end of the test
as we do in other tests. Sometimes test process crashes somewhere
in the middle (e.g. during race reporting) and it looks like empty output.
Output at the end of test allows to understand if the process has crashed,
or it has finished but produced no race reports.
Reviewed in https://reviews.llvm.org/D42633
llvm-svn: 323657
`set_target_compile_flags()` ultimately sets COMPILE_FLAGS which is
added to CMAKE_CXX_FLAGS in the compile rule, so passing
CMAKE_CXX_FLAGS causes them to be duplicated.
Differential Revision: https://reviews.llvm.org/D42398
llvm-svn: 323626
This gets rid of a lit warning (input './projects/compiler-rt/test/xray/Unit' contained no tests).
Differential Revision: https://reviews.llvm.org/D42597
llvm-svn: 323613
Clang and llvm already use llvm_setup_rpath(), so this change will
help standarize rpath usage across all projects.
Differential Revision: https://reviews.llvm.org/D42462
llvm-svn: 323606
Summary:
This is a follow-up to D42506.
There are a few of things that bothered me about `scudo_interceptors.cpp`:
- the filename is a misnomer: it intercepts some functions, but the rest (C++)
is actually in `scudo_new_delete.cpp`. I feel like `scudo_malloc.cpp` is more
appropriate (ASan uses the same naming scheme);
- we do not need "full" interceptors, since we are never accessing the
unsanitized version of the functions, we just need the
`extern "C" INTERCEPTOR_ATTRIBUTE` part of it to just call our functions;
- a couple of functions where duplicated while they could just be `ALIAS`'d;
- use the `SANITIZER_INTERCEPT_*` defines to hide the unneeded interceptors;
- use `SIZE_T` instead of `uptr`: while it's the same behind the curtain,
the former is meant for this use case.
In the end there is no functional change on the currently supported platforms
(Linux, Android).
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: mgorny, hintonda, delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42546
llvm-svn: 323464
Summary:
Implement `GetNumberOfCPUs` using `GetNativeSystemInfo`.
The only consummer of this function is Scudo which is not functional on
Windows yet.
Reviewers: rnk, zturner
Reviewed By: zturner
Subscribers: zturner, kubamracek, delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42547
llvm-svn: 323462
Summary:
Currently all platforms are using the `scudo_interceptors.cpp` interceptors.
We might to come up with platform specific interceptors when/if we get Apple &
Windows, but as of now, that allows for Fuchsia to use them.
`scudo_new_delete.cpp` didn't have the `#if SANITIZER_LINUX` so it's good to go.
Reviewers: alekseyshl, flowerhack
Reviewed By: flowerhack
Subscribers: delcypher, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42506
llvm-svn: 323386
Summary:
Hooks in the allocation & deallocation paths can be a security risk (see for an
example https://scarybeastsecurity.blogspot.com/2016/11/0day-exploit-advancing-exploitation.html
which used the glibc's __free_hook to complete exploitation).
But some users have expressed a need for them, even if only for tests and
memory benchmarks. So allow for `__sanitizer_malloc_hook` &
`__sanitizer_free_hook` to be called if defined, and gate them behind a global
define `SCUDO_CAN_USE_HOOKS` defaulting to 0.
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42430
llvm-svn: 323278
Summary:
Now that ubsan does function interception (for signals), we
need to ensure that ubsan is initialized before any library
constructors are called. Otherwise, if a constructor calls
sigaction, ubsan will intercept in an unitialized state, which
will cause a crash.
This patch is a partial revert of r317757, which removed
preinit arrays for ubsan.
Reviewers: vitalybuka, eugenis, pcc
Subscribers: kubamracek, mgorny, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D42389
llvm-svn: 323249
In more recent Linux kernels with 47 bit VMAs the layout of virtual memory
for powerpc64 changed causing the address sanitizer to not work properly. This
patch fixes up a test case that was found to fail on some newer Fedora
releases that use different address ranges.
ref: https://reviews.llvm.org/D40907
llvm-svn: 323217
Summary:
One test-case uses a wrong operation (should be subtraction).
Second test-case should declare a global variables before a tested one
in order to guarantee we will find a red-zone.
Reviewers: kcc, jakubjelinek, alekseyshl
Reviewed By: alekseyshl
Subscribers: kubamracek
Differential Revision: https://reviews.llvm.org/D41481
llvm-svn: 323162
add_custom_libcxx uses the just built compiler and installs the
built libc++, e.g. for testing, neither of which is desirable in
case of Fuzzer where the libc++ should be built using the host
compiler and it's only linked into the libFuzzer and should never
be installed. This change introduces additional arguments to
add_custom_libcxx to allow parametrizing its behavior.
Differential Revision: https://reviews.llvm.org/D42330
llvm-svn: 323054
add_custom_libcxx uses the just built compiler and installs the
built libc++, e.g. for testing, neither of which is desirable in
case of Fuzzer where the libc++ should be built using the host
compiler and it's only linked into the libFuzzer and should never
be installed. This change introduces additional arguments to
add_custom_libcxx to allow parametrizing its behavior.
Differential Revision: https://reviews.llvm.org/D42330
llvm-svn: 323032
sequentially.
The current implementation of commands in
`test/sanitizer_common/ios_commands/` for iOS devices cannot be executed
in parallel which results in the ASan and TSan tests failing when
executed in parallel by lit which was the default behaviour.
We now force the ASan and TSan tests to be a new parallelism group named
`darwin-ios-device-sanitizer` which allows only one test to be run at a
time. We also emit a warning informing the user that tests are being
run sequentially.
This only applies if the target is an iOS device.
Differential Revision: https://reviews.llvm.org/D42156
llvm-svn: 323026
MemToShadowImpl() maps lower addresses to a memory space out of sanitizers
range. The simplest example is address 0 which is mapped to 0x2000000000
static const uptr kShadowBeg = 0x2400000000ull;
but accessing the address during tsan execution will lead to a segmentation
fault.
This patch expands the range used by the sanitizer and ensures that 1/8 of
the maximum valid address in the virtual address spaces is used for shadow
memory.
Patch by Milos Stojanovic.
Differential Revision: https://reviews.llvm.org/D41777
llvm-svn: 323013
Summary:
We somehow never did it, and it raised no issue until now, when trying to
enable Fuchsia as a supported Scudo platform in the cmake config.
So propagate SANITIZER_COMMON_LINK_FLAGS for now.
Reviewers: alekseyshl, flowerhack
Reviewed By: flowerhack
Subscribers: mgorny, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42314
llvm-svn: 322999
Summary:
While there, unify InMemoryRawLog and InMemoryRawLogWithArg's coding style:
- swap libc's memcpy(3) for sanitizer's internal memcpy
- use basic pointer arithmetics to compute offsets from the first record
entry in the pre-allocated buffer, which is always the appropriate type
for the given function
- lose the local variable references as the TLD.* names fit just as well
Reviewers: eizan, kpw, dberris, dblaikie
Subscribers: #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42289
llvm-svn: 322941
Generalize this handling to a separate toplevel ifdef (since any
windows case should use the same function), instead of indenting
the aarch64 case one step further.
Differential Revision: https://reviews.llvm.org/D42197
llvm-svn: 322928
Summary:
Tests were being run by whole-linking the static library with our test binaries.
But since `-fsanitize=scudo` landed with rL317337, we might as well change how
the tests are compiled to use it.
The only difference will be on Android, where the clang flag links in the
dynamic library instead, but the bots are already pushing
`libclang_rt.*-android.so` to the device there is no additional change needed.
Tested locally, including with a standalone build, and an Android one on a O
device, and it all passes.
Reviewers: alekseyshl
Reviewed By: alekseyshl
Subscribers: #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42243
llvm-svn: 322882
Summary:
Make common allocator agnostic to failure handling modes and move the
decision up to the particular sanitizer's allocator, where the context
is available (call stack, parameters, return nullptr/crash mode etc.)
It simplifies the common allocator and allows the particular sanitizer's
allocator to generate more specific and detailed error reports (which
will be implemented later).
The behavior is largely the same, except one case, the violation of the
common allocator's check for "size + alignment" overflow is now reportied
as OOM instead of "bad request". It feels like a worthy tradeoff and
"size + alignment" is huge in this case anyway (thus, can be interpreted
as not enough memory to satisfy the request). There's also a Report()
statement added there.
Reviewers: eugenis
Subscribers: kubamracek, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D42198
llvm-svn: 322784
Summary:
A forgotten include in `scudo_allocator.cpp` made the symbol only local :/
Before:
```
nm ./lib/clang/7.0.0/lib/linux/libclang_rt.scudo-i686-android.so | grep rss
00024730 t __scudo_set_rss_limit
```
After:
```
nm ./lib/clang/7.0.0/lib/linux/libclang_rt.scudo-i686-android.so | grep rs
00024760 T __scudo_set_rss_limit
```
And we want `T`!
This include also means that we can get rid of the `extern "C"` in the C++
file, the compiler does fine without it (note that this was already the case
for all the `__sanitizer_*` interface functions.
Reviewers: alekseyshl, eugenis
Reviewed By: eugenis
Subscribers: #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42199
llvm-svn: 322782
Summary:
jemalloc on Android currently uses 2 arenas
(https://android.googlesource.com/platform/external/jemalloc/+/master/Android.bp#64).
Since the Android toolchain absorbs compiler-rt and compiles it as is, we have
to enforce the same limit to somehow stay competitive in terms of memory usage.
The changes could either go in:
- `scudo_platform.h` with a default for Android of 2 (this is the solution
implemented here);
- in `CMakeLists.txt` adding -DSCUDO_SHARED_TSD_POOL_SIZE=2 for Android.
- something else?
I don't have a strong opinion on how to do it, but it has to be done upstream
anyway.
Reviewers: alekseyshl, eugenis
Reviewed By: alekseyshl, eugenis
Subscribers: srhines, #sanitizers, llvm-commits
Differential Revision: https://reviews.llvm.org/D42194
llvm-svn: 322764
This is needed in case the users of libFuzzer use libc++ in their
code, which the fuzz target (libFuzzer) will be linked against.
When libc++ source is available, we build a private version of it
and link it against libFuzzer which allows using the same static
library against codebases which use both libc++ and libstdc++.
Differential Revision: https://reviews.llvm.org/D37631
llvm-svn: 322755
Summary:
This patch (on top of the previous two (https://reviews.llvm.org/D40898 and
https://reviews.llvm.org/D40899) complete the compiler-rt side of the the Solaris
sanitizer port.
It contains the following sets of changes:
* For the time being, the port is for 32-bit x86 only, so reject the various tests on
x86_64.
* When compiling as C++, <setjmp.h> resp. <iso/setjmp_iso.h> only declares
_setjmp and _longjmp inside namespace std.
* MAP_FILE is a Windows feature. While e.g. Linux <sys/mman.h> provides a
no-op compat define, Solaris does not.
* test/asan/TestCases/Posix/coverage.cc was initially failing like this:
/vol/gcc/src/llvm/llvm/local/projects/compiler-rt/lib/sanitizer_common/scripts/sancov.py: 4 files merged; 2 PCs total
rm: cannot remove '/var/gcc/llvm/local/projects/compiler-rt/test/asan/I386SunOSConfig/TestCases/Posix/Output/coverage': Invalid argument
Further digging revealed that the rm was trying to remove the running test's working
directory which failed as observed. cd'ing out of the dir before let the test pass.
* Two tests needed a declaration of alloca. I've now copied the existing code from
test/asan/TestCases/alloca_constant_size.cc, but it may be more profitable and
maintainable to have a common testsuite header where such code is collected.
* Similarly, Solaris' printf %p format doesn't include the leading 0x.
* In test/asan/TestCases/malloc-no-intercept.c, I had to undef __EXTENSIONS__
(predefined by clang for no apparent reason) to avoid conflicting declarations
for memalign.
* test/ubsan/TestCases/Float/cast-overflow.cpp has different platform dependent
ways to define BYTE_ORDER and friends. Why not just use __BYTE_ORDER__ and
friends as predefined by clang and gcc?
Patch by Rainer Orth.
Reviewers: kcc, alekseyshl
Reviewed By: alekseyshl
Subscribers: srhines, kubamracek, mgorny, krytarowski, fedor.sergeev, JDevlieghere, llvm-commits, #sanitizers
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D40900
llvm-svn: 322635
This is needed in case the users of libFuzzer use libc++ in their
code, which the fuzz target (libFuzzer) will be linked against.
When libc++ source is available, we build a private version of it
and link it against libFuzzer which allows using the same static
library against codebases which use both libc++ and libstdc++.
Differential Revision: https://reviews.llvm.org/D37631
llvm-svn: 322604
Summary: -fPIE can not be used when building a shared library.
Reviewers: alekseyshl, peter.smith
Subscribers: kubamracek, llvm-commits, mgorny
Differential Revision: https://reviews.llvm.org/D42121
llvm-svn: 322588
Currently these files are being installed into a root installation
directory, but this triggers an error when the installation directory
is set to an empty string which is often the case when DESTDIR is
used to control the installation destination.
Differential Revision: https://reviews.llvm.org/D41673
llvm-svn: 322451
Summary:
Some time ago, the sanitizers as of r315899 were imported into gcc mainline. This broke
bootstrap on Darwin 10 and 11, as reported in GCC PR sanitizer/82824
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82824) due to the unconditional use
of VM_MEMORY_OS_ALLOC_ONCE. This was only introduced in Darwin 13/Mac OS X 10.9.
The use of the macro was introduced in r300450.
I couldn't find any statement which Darwin versions are supposed to be supported by
LLVM, but the trivial patch to use the macro only if present allowed the gcc bootstrap
to finish.
So far, I haven't tried building llvm/compiler-rt on Darwin 11. Maybe the patch is
simple enough to go in nonetheless.
Committing on behalf of ro.
Reviewers: glider, fjricci, kcc, kuba, kubamracek, george.karpenkov
Reviewed By: fjricci
Subscribers: #sanitizers, zaks.anna, srhines, dberris, kubamracek, llvm-commits
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D39888
llvm-svn: 322437
Summary: It is not necessary launching the build script with bash.
Reviewers: krytarowski
Reviewed By: krytarowski
Subscribers: llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D42008
llvm-svn: 322422
Summary:
itimerval can contain padding that may be legitimately uninitialized.
On NetBSD there are four integers of type "long, int, long, int", the
int argument stands for __sanitizer_suseconds_t. Compiler adds extra
padding in this layout.
Check every field of struct itimerval separately.
Define __sanitizer_suseconds_t as long on FreeBSD, Linux and SmartOS,
and int on NetBSD. Define __sanitizer_timeval and __sanitizer_itimerval.
Sponsored by <The NetBSD Foundation>
Reviewers: eugenis, joerg, vitalybuka
Reviewed By: vitalybuka
Subscribers: emaste, kubamracek, llvm-commits, #sanitizers
Tags: #sanitizers
Differential Revision: https://reviews.llvm.org/D41502
llvm-svn: 322399
Summary:
This is needed for the shared runtime since we are pulling RTUbsan in.
Otherwise some builds might fail with errors such as:
`error: undefined reference to '__dynamic_cast'`
Reviewers: alekseyshl, srhines
Reviewed By: srhines
Subscribers: kongyi, pirama, chh, mgorny, llvm-commits, #sanitizers
Differential Revision: https://reviews.llvm.org/D41995
llvm-svn: 322389
Summary:
Very basic stack instrumentation using tagged pointers.
Tag for N'th alloca in a function is built as XOR of:
* base tag for the function, which is just some bits of SP (poor
man's random)
* small constant which is a function of N.
Allocas are aligned to 16 bytes. On every ReturnInst allocas are
re-tagged to catch use-after-return.
This implementation has a bunch of issues that will be taken care of
later:
1. lifetime intrinsics referring to tagged pointers are not
recognized in SDAG. This effectively disables stack coloring.
2. Generated code is quite inefficient. There is one extra
instruction at each memory access that adds the base tag to the
untagged alloca address. It would be better to keep tagged SP in a
callee-saved register and address allocas as an offset of that XOR
retag, but that needs better coordination between hwasan
instrumentation pass and prologue/epilogue insertion.
3. Lifetime instrinsics are ignored and use-after-scope is not
implemented. This would be harder to do than in ASan, because we
need to use a differently tagged pointer depending on which
lifetime.start / lifetime.end the current instruction is dominated
/ post-dominated.
Reviewers: kcc, alekseyshl
Subscribers: srhines, kubamracek, javed.absar, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D41602
llvm-svn: 322324
Rafael Espindola