Merge clang, llvm, lld, lldb, compiler-rt and libc++ 6.0.0 release, and

Merge clang, llvm, lld, lldb, compiler-rt and libc++ 6.0.0 release, and
several follow-up fixes.

MFC r327952:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
6.0.0 (branches/release_60 r321788).  Upstream has branched for the
6.0.0 release, which should be in about 6 weeks.  Please report bugs and
regressions, so we can get them into the release.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

MFC r328010:

Pull in r322473 from upstream llvm trunk (by Andrei Elovikov):

  [LV] Don't call recordVectorLoopValueForInductionCast for
  newly-created IV from a trunc.

  Summary:
  This method is supposed to be called for IVs that have casts in their
  use-def chains that are completely ignored after vectorization under
  PSE. However, for truncates of such IVs the same InductionDescriptor
  is used during creation/widening of both original IV based on PHINode
  and new IV based on TruncInst.

  This leads to unintended second call to
  recordVectorLoopValueForInductionCast with a VectorLoopVal set to the
  newly created IV for a trunc and causes an assert due to attempt to
  store new information for already existing entry in the map. This is
  wrong and should not be done.

  Fixes PR35773.

  Reviewers: dorit, Ayal, mssimpso

  Reviewed By: dorit

  Subscribers: RKSimon, dim, dcaballe, hsaito, llvm-commits, hiraditya

  Differential Revision: https://reviews.llvm.org/D41913

This should fix "Vector value already set for part" assertions when
building the net/iodine and sysutils/daa2iso ports.

Reported by:	jbeich
PR:		224867, 224868

MFC r328090:

Pull in r322623 from upstream llvm trunk (by Andrew V. Tischenko):

  Allow usage of X86-prefixes as separate instrs.
  Differential Revision: https://reviews.llvm.org/D42102

This should fix parse errors when x86 prefixes (such as 'lock' and
'rep') are followed by various non-mnemonic tokens, e.g. comments, .byte
directives and labels.

PR:		224669, 225054

MFC r328091:

Revert r327340, as the workaround for rep prefixes followed by .byte
directives is no longer needed after r328090.

MFC r328141 (by emaste):

lld: Fix for ld.lld does not accept "AT" syntax for declaring LMA region

AT> lma_region expression allows to specify the memory region
for section load address.

Should fix [upstream LLVM] PR35684.

LLVM review: https://reviews.llvm.org/D41397

Obtained from:	LLVM r322359 by George Rimar

MFC r328143 (by emaste):

lld: Handle parsing AT(ADDR(.foo-bar)).

The problem we had with it is that anything inside an AT is an
expression, so we failed to parse the section name because of the - in
it.

Requested by:	royger
Obtained from:	LLVM r322801 by Rafael Espindola

MFC r328144 (by emaste):

lld: Fix incorrect physical address on self-referencing AT command.

When a section placement (AT) command references the section itself,
the physical address of the section in the ELF header was calculated
incorrectly due to alignment happening right after the location
pointer's value was captured.

The problem was diagnosed and the first version of the patch written
by Erick Reyes.

Obtained from:	LLVM r322421 by Rafael Espindola

MFC r328145:

Pull in r322016 from upstream llvm trunk (by Sanjay Patel):

  [ValueTracking] remove overzealous assert

  The test is derived from a failing fuzz test:
  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=5008

  Credit to @rksimon for pointing out the problem.

This should fix "Bad flavor while matching min/max" errors when building
the graphics/libsixel and science/kst2 ports.

Reported by:	jbeich
PR:		225268, 225269

MFC r328146:

Pull in r322106 from upstream llvm trunk (by Alexey Bataev):

  [COST]Fix PR35865: Fix cost model evaluation for shuffle on X86.

  Summary:
  If the vector type is transformed to non-vector single type, the
  compile may crash trying to get vector information about non-vector
  type.

  Reviewers: RKSimon, spatel, mkuper, hfinkel

  Subscribers: llvm-commits

  Differential Revision: https://reviews.llvm.org/D41862

This should fix "Not a vector MVT!" errors when building the
games/dhewm3 port.

Reported by:	jbeich
PR:		225271

MFC r328286 (by emaste):

lld: Don't mark a shared library as needed because of a lazy symbol.

Obtained from:	LLVM r323221 by Rafael Esp?ndola

MFC r328381:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
6.0.0 (branches/release_60 r323338).

PR:		224669

MFC r328513:

Pull in r322245 from upstream clang trunk (by Craig Topper):

  [X86] Make -mavx512f imply -mfma and -mf16c in the frontend like it
  does in the backend.

  Similarly, make -mno-fma and -mno-f16c imply -mno-avx512f.

  Withou this  "-mno-sse -mavx512f" ends up with avx512f being enabled
  in the frontend but disabled in the backend.

Reported by:	pawel
PR:		225488

MFC r328542 (by emaste):

lld: Use lookup instead of find. NFC, just simpler.

Obtained from:	LLVM r323395 by Rafael Espindola

MFC r328543 (by emaste):

lld: Only lookup LMARegion once. NFC.

This is similar to how we handle MemRegion.

Obtained from:	LLVM r323396 by Rafael Espindola

MFC r328544 (by emaste):

lld: Remove MemRegionOffset. NFC.

We can just use a member variable in MemoryRegion.

Obtained from:	LLVM r323399 by Rafael Espindola

MFC r328545 (by emaste):

lld: Simplify. NFC.

Obtained from:	LLVM r323440 by Rafael Espindola

MFC r328546 (by emaste):

lld: Improve LMARegion handling.

This fixes the crash reported at [LLVM] PR36083.

The issue is that we were trying to put all the sections in the same
PT_LOAD and crashing trying to write past the end of the file.

This also adds accounting for used space in LMARegion, without it all
3 PT_LOADs would have the same physical address.

Obtained from:	LLVM r323449 by Rafael Espindola

MFC r328547 (by emaste):

lld: Move LMAOffset from the OutputSection to the PhdrEntry. NFC.

If two sections are in the same PT_LOAD, their relatives offsets,
virtual address and physical addresses are all the same.

[Rafael] initially wanted to have a single global LMAOffset, on the
assumption that every ELF file was in practiced loaded contiguously in
both physical and virtual memory.

Unfortunately that is not the case. The linux kernel has:

  LOAD           0x200000 0xffffffff81000000 0x0000000001000000 0xced000 0xced000 R E 0x200000
  LOAD           0x1000000 0xffffffff81e00000 0x0000000001e00000 0x15f000 0x15f000 RW  0x200000
  LOAD           0x1200000 0x0000000000000000 0x0000000001f5f000 0x01b198 0x01b198 RW  0x200000
  LOAD           0x137b000 0xffffffff81f7b000 0x0000000001f7b000 0x116000 0x1ec000 RWE 0x200000

The delta for all but the third PT_LOAD is the same:
0xffffffff80000000. [Rafael] thinks the 3rd one is a hack for implementing
per cpu data, but we can't break that.

Obtained from:	LLVM r323456 by Rafael Espindola

MFC r328548 (by emaste):

lld: Put the header in the first PT_LOAD even if that PT_LOAD has a LMAExpr

The root problem is that we were creating a PT_LOAD just for the header.
That was technically valid, but inconvenient: we should not be making
the ELF discontinuous.

The solution is to allow a section with LMAExpr to be added to a PT_LOAD
if that PT_LOAD doesn't already have a LMAExpr.

LLVM PR:	36017
Obtained from:	LLVM r323625 by Rafael Espindola

MFC r328594 (by emaste):

Pull in r322108 from upstream llvm trunk (by Rafael Esp?ndola):

  Make one of the emitFill methods non virtual. NFC.

  This is just preparatory work to fix [LLVM] PR35858.

MFC r328595 (by emaste):

Pull in r322123 from upstream llvm trunk (by Rafael Esp?ndola):

  Don't create MCFillFragment directly.

  Instead use higher level APIs that take care of most bookkeeping.

MFC r328596 (by emaste):

Pull in r322131 from upstream llvm trunk (by Rafael Esp?ndola):

  Use a MCExpr for the size of MCFillFragment.

  This allows the size to be found during ralaxation. This fixes
  [LLVM] pr35858.

Requested by:	royger

MFC r328753:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
6.0.0 (branches/release_60 r323948).

PR:		224669

MFC r328817:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
6.0.0 (branches/release_60 r324090).

This introduces retpoline support, with the -mretpoline flag.  The
upstream initial commit message (r323155 by Chandler Carruth) contains
quite a bit of explanation.  Quoting:

  Introduce the "retpoline" x86 mitigation technique for variant #2 of
  the speculative execution vulnerabilities disclosed today,
  specifically identified by CVE-2017-5715, "Branch Target Injection",
  and is one of the two halves to Spectre.

  Summary:
  First, we need to explain the core of the vulnerability. Note that
  this is a very incomplete description, please see the Project Zero
  blog post for details:
  https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html

  The basis for branch target injection is to direct speculative
  execution of the processor to some "gadget" of executable code by
  poisoning the prediction of indirect branches with the address of
  that gadget. The gadget in turn contains an operation that provides a
  side channel for reading data. Most commonly, this will look like a
  load of secret data followed by a branch on the loaded value and then
  a load of some predictable cache line. The attacker then uses timing
  of the processors cache to determine which direction the branch took
  *in the speculative execution*, and in turn what one bit of the
  loaded value was. Due to the nature of these timing side channels and
  the branch predictor on Intel processors, this allows an attacker to
  leak data only accessible to a privileged domain (like the kernel)
  back into an unprivileged domain.

  The goal is simple: avoid generating code which contains an indirect
  branch that could have its prediction poisoned by an attacker. In
  many cases, the compiler can simply use directed conditional branches
  and a small search tree. LLVM already has support for lowering
  switches in this way and the first step of this patch is to disable
  jump-table lowering of switches and introduce a pass to rewrite
  explicit indirectbr sequences into a switch over integers.

  However, there is no fully general alternative to indirect calls. We
  introduce a new construct we call a "retpoline" to implement indirect
  calls in a non-speculatable way. It can be thought of loosely as a
  trampoline for indirect calls which uses the RET instruction on x86.
  Further, we arrange for a specific call->ret sequence which ensures
  the processor predicts the return to go to a controlled, known
  location. The retpoline then "smashes" the return address pushed onto
  the stack by the call with the desired target of the original
  indirect call. The result is a predicted return to the next
  instruction after a call (which can be used to trap speculative
  execution within an infinite loop) and an actual indirect branch to
  an arbitrary address.

  On 64-bit x86 ABIs, this is especially easily done in the compiler by
  using a guaranteed scratch register to pass the target into this
  device.  For 32-bit ABIs there isn't a guaranteed scratch register
  and so several different retpoline variants are introduced to use a
  scratch register if one is available in the calling convention and to
  otherwise use direct stack push/pop sequences to pass the target
  address.

  This "retpoline" mitigation is fully described in the following blog
  post: https://support.google.com/faqs/answer/7625886

  We also support a target feature that disables emission of the
  retpoline thunk by the compiler to allow for custom thunks if users
  want them.  These are particularly useful in environments like
  kernels that routinely do hot-patching on boot and want to hot-patch
  their thunk to different code sequences. They can write this custom
  thunk and use `-mretpoline-external-thunk` *in addition* to
  `-mretpoline`. In this case, on x86-64 thu thunk names must be:
  ```
    __llvm_external_retpoline_r11
  ```
  or on 32-bit:
  ```
    __llvm_external_retpoline_eax
    __llvm_external_retpoline_ecx
    __llvm_external_retpoline_edx
    __llvm_external_retpoline_push
  ```
  And the target of the retpoline is passed in the named register, or in
  the case of the `push` suffix on the top of the stack via a `pushl`
  instruction.

  There is one other important source of indirect branches in x86 ELF
  binaries: the PLT. These patches also include support for LLD to
  generate PLT entries that perform a retpoline-style indirection.

  The only other indirect branches remaining that we are aware of are
  from precompiled runtimes (such as crt0.o and similar). The ones we
  have found are not really attackable, and so we have not focused on
  them here, but eventually these runtimes should also be replicated for
  retpoline-ed configurations for completeness.

  For kernels or other freestanding or fully static executables, the
  compiler switch `-mretpoline` is sufficient to fully mitigate this
  particular attack. For dynamic executables, you must compile *all*
  libraries with `-mretpoline` and additionally link the dynamic
  executable and all shared libraries with LLD and pass `-z
  retpolineplt` (or use similar functionality from some other linker).
  We strongly recommend also using `-z now` as non-lazy binding allows
  the retpoline-mitigated PLT to be substantially smaller.

  When manually apply similar transformations to `-mretpoline` to the
  Linux kernel we observed very small performance hits to applications
  running typic al workloads, and relatively minor hits (approximately
  2%) even for extremely syscall-heavy applications. This is largely
  due to the small number of indirect branches that occur in
  performance sensitive paths of the kernel.

  When using these patches on statically linked applications,
  especially C++ applications, you should expect to see a much more
  dramatic performance hit. For microbenchmarks that are switch,
  indirect-, or virtual-call heavy we have seen overheads ranging from
  10% to 50%.

  However, real-world workloads exhibit substantially lower performance
  impact. Notably, techniques such as PGO and ThinLTO dramatically
  reduce the impact of hot indirect calls (by speculatively promoting
  them to direct calls) and allow optimized search trees to be used to
  lower switches. If you need to deploy these techniques in C++
  applications, we *strongly* recommend that you ensure all hot call
  targets are statically linked (avoiding PLT indirection) and use both
  PGO and ThinLTO. Well tuned servers using all of these techniques saw
  5% - 10% overhead from the use of retpoline.

  We will add detailed documentation covering these components in
  subsequent patches, but wanted to make the core functionality
  available as soon as possible. Happy for more code review, but we'd
  really like to get these patches landed and backported ASAP for
  obvious reasons. We're planning to backport this to both 6.0 and 5.0
  release streams and get a 5.0 release with just this cherry picked
  ASAP for distros and vendors.

  This patch is the work of a number of people over the past month:
  Eric, Reid, Rui, and myself. I'm mailing it out as a single commit
  due to the time sensitive nature of landing this and the need to
  backport it. Huge thanks to everyone who helped out here, and
  everyone at Intel who helped out in discussions about how to craft
  this. Also, credit goes to Paul Turner (at Google, but not an LLVM
  contributor) for much of the underlying retpoline design.

  Reviewers: echristo, rnk, ruiu, craig.topper, DavidKreitzer

  Subscribers: sanjoy, emaste, mcrosier, mgorny, mehdi_amini, hiraditya, llvm-commits

  Differential Revision: https://reviews.llvm.org/D41723

PR:		224669

MFC r329033:

Pull in r324594 from upstream clang trunk (by Alexander Ivchenko):

  Fix for #31362 - ms_abi is implemented incorrectly for values >=16
  bytes.

  Summary:
  This patch is a fix for following issue:
  https://bugs.llvm.org/show_bug.cgi?id=31362 The problem was caused by
  front end lowering C calling conventions without taking into account
  calling conventions enforced by attribute. In this case win64cc was
  no correctly lowered on targets other than Windows.

  Reviewed By: rnk (Reid Kleckner)

  Differential Revision: https://reviews.llvm.org/D43016

  Author: belickim <mateusz.belicki@intel.com>

This fixes clang 6.0.0 assertions when building the emulators/wine and
emulators/wine-devel ports, and should also make it use the correct
Windows calling conventions.  Bump __FreeBSD_version to make the fix
easy to detect.

PR:		224863

MFC r329223:

Pull in r323998 from upstream clang trunk (by Richard Smith):

  PR36157: When injecting an implicit function declaration in C89, find
  the right DeclContext rather than injecting it wherever we happen to
  be.

  This avoids creating functions whose DeclContext is a struct or
  similar.

This fixes assertion failures when parsing certain not-completely-valid
struct declarations.

Reported by:	ae
PR:		225862

MFC r329410:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
6.0.0 (branches/release_60 r325330).

PR:		224669

MFC r329983:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
6.0.0 (branches/release_60 r325932).  This corresponds to 6.0.0 rc3.

PR:		224669

MFC r330384:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
6.0.0 release (upstream r326565).

Release notes for llvm, clang and lld will be available here soon:
<http://releases.llvm.org/6.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/6.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/6.0.0/tools/lld/docs/ReleaseNotes.html>

Relnotes:	yes
PR:		224669

MFC r330686:

Pull in r326882 from upstream llvm trunk (by Sjoerd Meijer):

  [ARM] Fix for PR36577

  Don't PerformSHLSimplify if the given node is used by a node that
  also uses a constant because we may get stuck in an infinite combine
  loop.

  bugzilla: https://bugs.llvm.org/show_bug.cgi?id=36577

  Patch by Sam Parker.

  Differential Revision: https://reviews.llvm.org/D44097

This fixes a hang when compiling one particular file in java/openjdk8
for armv6 and armv7.

Reported by:	swills
PR:		226388

MFC r331065:

Pull in r327638 from upstream llvm trunk (by Matthew Simpson):

  [ConstantFolding, InstSimplify] Handle more vector GEPs

  This patch addresses some additional cases where the compiler crashes
  upon encountering vector GEPs. This should fix PR36116.

  Differential Revision: https://reviews.llvm.org/D44219
  Reference: https://bugs.llvm.org/show_bug.cgi?id=36116

This fixes an assertion when building the emulators/snes9x port.

Reported by:	jbeich
PR:		225471

MFC r331066:

Pull in r321999 from upstream clang trunk (by Ivan A. Kosarev):

  [CodeGen] Fix TBAA info for accesses to members of base classes

  Resolves:
  Bug 35724 - regression (r315984): fatal error: error in backend:
  Broken function found (Did not see access type in access path!)
  https://bugs.llvm.org/show_bug.cgi?id=35724

  Differential Revision: https://reviews.llvm.org/D41547

This fixes "Did not see access type in access path" fatal errors when
building the devel/gdb port (version 8.1).

Reported by:	jbeich
PR:		226658

MFC r331366:

Pull in r327101 from upstream llvm trunk (by Rafael Espindola):

  Don't treat .symver as a regular alias definition.

  This patch starts simplifying the handling of .symver.

  For now it just moves the responsibility for creating an alias down to
  the streamer. With that the asm streamer can pass a .symver unchanged,
  which is nice since gas cannot parse "foo@bar = zed".

  In a followup I hope to move the handling down to the writer so that
  we don't need special hacks for avoiding breaking names with @@@ on
  windows.

Pull in r327160 from upstream llvm trunk (by Rafael Espindola):

  Delay creating an alias for @@@.

  With this we only create an alias for @@@ once we know if it should
  use @ or @@. This avoids last minutes renames and hacks to handle MS
  names.

  This only handles the ELF writer. LTO still has issues with @@@
  aliases.

Pull in r327928 from upstream llvm trunk (by Vitaly Buka):

  Object: Move attribute calculation into RecordStreamer. NFC

  Summary: Preparation for D44274

  Reviewers: pcc, espindola

  Subscribers: hiraditya

  Differential Revision: https://reviews.llvm.org/D44276

Pull in r327930 from upstream llvm trunk (by Vitaly Buka):

  Object: Fix handling of @@@ in .symver directive

  Summary:
  name@@@nodename is going to be replaced with name@@nodename if symbols is
  defined in the assembled file, or name@nodename if undefined.
  https://sourceware.org/binutils/docs/as/Symver.html

  Fixes PR36623

  Reviewers: pcc, espindola

  Subscribers: mehdi_amini, hiraditya

  Differential Revision: https://reviews.llvm.org/D44274

Together, these changes fix handling of @@@ in .symver directives when
doing Link Time Optimization.

Reported by:	Shawn Webb <shawn.webb@hardenedbsd.org>

MFC r331731:

Pull in r328738 from upstream lld trunk (by Rafael Espindola):

  Strip @VER suffices from the LTO output.

  This fixes pr36623.

  The problem is that we have to parse versions out of names before LTO
  so that LTO can use that information.

  When we get the LTO produced .o files, we replace the previous symbols
  with the LTO produced ones, but they still have @ in their names.

  We could just trim the name directly, but calling parseSymbolVersion
  to do it is simpler.

This is a follow-up to r331366, since we discovered that lld could
append version strings to symbols twice, when using Link Time
Optimization.