Commit Graph

332653 Commits

Author SHA1 Message Date
Rui Ueyama 3f76260dc0 Use InitLLVM to setup a pretty stack printer
InitLLVM does not only save a few lines from main() but also makes the
commands do the right thing for multibyte character pathnames on
Windows (i.e. canonicalize argv's to UTF-8) because of the code we
have in this file:

https://github.com/llvm/llvm-project/blob/master/llvm/lib/Support/InitLLVM.cpp#L32

For many LLVM commands, we already have calls of InitLLVM, but there
are still remainings.

Differential Revision: https://reviews.llvm.org/D70702
2019-11-26 10:56:10 +09:00
Evgenii Stepanov 06d1110584 Speculative fix for frame-loclist.s test on Windows.
"echo -e" treats windows paths as special characters (ex. "\b").
2019-11-25 17:51:15 -08:00
Eric Christopher 8ff85ed905 As a follow-up to my initial mail to llvm-dev here's a first pass at the O1 described there.
This change doesn't include any change to move from selection dag to fast isel
and that will come with other numbers that should help inform that decision.
There also haven't been any real debuggability studies with this pipeline yet,
this is just the initial start done so that people could see it and we could start
tweaking after.

Test updates: Outside of the newpm tests most of the updates are coming from either
optimization passes not run anymore (and without a compelling argument at the moment)
that were largely used for canonicalization in clang.

Original post:

http://lists.llvm.org/pipermail/llvm-dev/2019-April/131494.html

Tags: #llvm
Differential Revision: https://reviews.llvm.org/D65410
2019-11-25 17:16:46 -08:00
Craig Topper 3687ddef2c [X86] Add proper execution domain information to the avx512vnni instructions. 2019-11-25 17:07:35 -08:00
Craig Topper 890c6ef1fb [X86] Remove forward declaration of _invpcid from intrin.h. Rely on inline version from immintrin.h
The forward declaration had a cdecl calling convention, but the
inline version did not. This leads to a conflict if the default
calling convention is not cdecl. Fix this by just removing the
forward declaration.

Fixes PR41503
2019-11-25 16:27:39 -08:00
Alina Sbirlea 14a2bbb1ff [MemorySSA] Combine verifications.
Summary:
Combine three verification methods into one to improve compile time when asserts are enabled.
Motivated by PR44066.

Sample change of timings on testcase in PR44066 (release+asserts):
MSSA off or verification disabled: 1.13s.
MSSA on (ToT): 2.48s.
With patch: 2.03s.
With enabling DefUses after combining Domination+Ordering: 2.6s.
After also combining DefUses with Domination+Ordering: 2.06s (candidate to be taken out of EXPENSIVE_CHECKS).

Subscribers: Prazek, hiraditya, george.burgess.iv, sanjoy.google, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70618
2019-11-25 16:05:38 -08:00
Evgenii Stepanov 5906fb682d Fix new llvm-symbolizer tests on Windows.
A forward-slash vs backward-slash issue.
2019-11-25 15:59:13 -08:00
Nico Weber 94daffdfc6 gn build: (manually) merge 9e676d9c7e 2019-11-25 18:48:10 -05:00
Craig Topper a64dc93ab3 [X86] Add test case for pr44140. NFC 2019-11-25 15:38:24 -08:00
Eric Christopher e807569258 Fix an unused variable warning where a variable was only used in an assert. 2019-11-25 15:29:33 -08:00
Peter Collingbourne 90b8bc003c IRGen: Call SetLLVMFunctionAttributes{,ForDefinition} on __cfi_check_fail.
This has the main effect of causing target-cpu and target-features to be set
on __cfi_check_fail, causing the function to become ABI-compatible with other
functions in the case where these attributes affect ABI (e.g. reserve-x18).

Technically we only need to call SetLLVMFunctionAttributes to get the target-*
attributes set, but since we're creating a definition we probably ought to
call the ForDefinition function as well.

Fixes PR44094.

Differential Revision: https://reviews.llvm.org/D70692
2019-11-25 15:16:43 -08:00
Evgenii Stepanov 1b42cc0df1 llvm-symbolizer: fix handling of DW_AT_specification in FRAME.
Summary:
Use getSubroutineName() to the the subrouting name; this function knows
how to handle cases when DW_TAG_subprogram refers to an earlier
declaration:

0x00000050:     DW_TAG_subprogram
                  DW_AT_linkage_name    ("_ZN1A1fEv")
                  DW_AT_name    ("f")
...
0x00000067:   DW_TAG_subprogram
                DW_AT_low_pc    (0x0000000000000000)
                DW_AT_high_pc   (0x0000000000000020)
                DW_AT_specification     (0x00000050 "_ZN1A1fEv")
...
0x0000008c:     DW_TAG_variable

Reviewers: pcc, vitalybuka, jdoerfert

Subscribers: srhines, hiraditya, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70630
2019-11-25 15:06:07 -08:00
Evgenii Stepanov 9f60820d84 llvm-symbolizer: Support loclist in FRAME.
Summary:
Support location lists in FRAME command.
These are used for the majority of local variables in optimized code.
Also support DW_OP_breg in addition to DW_OP_fbreg when it refers to the
same register as DW_AT_frame_base.

Reviewers: pcc, jdoerfert

Subscribers: srhines, hiraditya, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70629
2019-11-25 15:06:07 -08:00
Evgenii Stepanov 1c33d7130e llvm-symbolizer: Fix FRAME handling of missing AT_name.
Summary:
llvm-symbolizer protocol is empty string means end-of-output.
Do not emit empty string when a function or a variable do not have a
name for any reason. Emit "??".

Reviewers: pcc, vitalybuka, jdoerfert

Subscribers: srhines, hiraditya, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70626
2019-11-25 14:55:11 -08:00
Fangrui Song f0558f582a [ELF] Delete unused Configuration::zExecstack after D56554 2019-11-25 14:44:09 -08:00
Evgenii Stepanov 947f969244 Fix sanitizer-common build with glibc 2.31
Summary:
As mentioned in D69104, glibc changed ABI recently with the [[ https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=2f959dfe849e0646e27403f2e4091536496ac0f0| 2f959dfe ]] change.
D69104 dealt with just 32-bit ARM, but that is just one of the many affected architectures.
E.g. x86_64, i?86, riscv64, sparc 32-bit, s390 31-bit are affected too (and various others).

This patch instead of adding a long list of further architectures that wouldn't be checked ever next to arm 32-bit changes the structures to match the 2.31 layout and performs the checking on Linux for ipc_perm mode position/size only on non-Linux or on Linux with glibc 2.31 or later.  I think this matches what is done for aarch64 already.
If needed, we could list architectures that haven't changed ABI (e.g. powerpc), so that they would be checked even with older glibcs.  AFAIK sanitizers don't actually use ipc_perm.mode and
so all they care about is the size and alignment of the whole structure.

Note, s390 31-bit and arm 32-bit big-endian changed ABI even further, there will now be shmctl with old symbol version and shmctl@@GLIBC_2.31 which will be incompatible.  I'm afraid this isn't really solvable unless the sanitizer libraries are symbol versioned and use matching symbol versions to glibc symbols for stuff they intercept, plus use dlvsym.
This patch doesn't try to address that.

Patch by Jakub Jelinek.

Reviewers: kcc, eugenis, dvyukov

Reviewed By: eugenis

Subscribers: jyknight, kristof.beyls, fedor.sergeev, simoncook, PkmX, s.egerton, steven.zhang, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D70662
2019-11-25 14:38:10 -08:00
Aaron Ballman d930ed1acc Disallow use of __has_c_attribute in C++ mode.
__has_cpp_attribute is not available in C mode, and __has_c_attribute
should not be available in C++ mode. This also adds a test to
demonstrate that we properly handle scoped attribute tokens even in C
mode.
2019-11-25 17:35:12 -05:00
Sanjay Patel 214683f3b2 [DAGCombiner] avoid crash on out-of-bounds insert index (PR44139)
We already have this simplification at node-creation-time, but
the test from:
https://bugs.llvm.org/show_bug.cgi?id=44139
...shows that we can combine our way to an assert/crash too.
2019-11-25 16:24:06 -05:00
Tom Stellard 3c5142597a Revert "[Diagnostic] add a warning which warns about misleading indentation"
This reverts commit 7b86188b50.

This commit introduced bot falures for multi-stage bots with -Werror.
2019-11-25 13:19:57 -08:00
Tom Stellard 0e12815566 Revert "[Diagnostics] Put "deprecated copy" warnings into -Wdeprecated-copy"
This reverts commit 9353c5dd06.

This commit introduced bot falures for multi-stage bots with -Werror.
2019-11-25 13:19:57 -08:00
Bardia Mahjour 67f0685b4d Revert "[DDG] Data Dependence Graph - Topological Sort"
Revert for now to look into the failures  on x86

This reverts commit bec37c3fc7.
2019-11-25 16:17:41 -05:00
Lei Huang 9e676d9c7e [PowerPC][compiler-rt][builtins]Add __fixtfti builtin on PowerPC
Implements __fixtfti builtin for PowerPC. This builtin converts a
long double (IBM double-double) to a signed int128. The conversion relies on
the unsigned conversion of the absolute value of the long double.

Tests included for both positive and negative long doubles.

Patch By: Baptiste Saleil

Differential Revision: https://reviews.llvm.org/D69730
2019-11-25 14:54:03 -06:00
Mitch Phillips 19edfb3728 [GWP-ASan] Add GWP_ASAN_ prefix to macros.
Summary:
When platforms use their own `LIKELY()` definitions, it can be quite
troublesome to ensure they don't conflict with the GWP-ASan internal
definitions. Just force the GWP_ASAN_ prefix to help this issue.

Reviewers: eugenis

Reviewed By: eugenis

Subscribers: #sanitizers, llvm-commits, cferris, pcc

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D70683
2019-11-25 12:27:00 -08:00
Kit Barton 85e4f5bcf6 [PowerPC] Rename DarwinDirective to CPUDirective (NFC)
Summary:
This patch renames the DarwinDirective (used to identify which CPU was defined)
to CPUDirective. It also adds the getCPUDirective() method and replaces all uses
of getDarwinDirective() with getCPUDirective().

Once this patch lands and downstream users of the getDarwinDirective() method
have switched to the getCPUDirective() method, the old getDarwinDirective()
method will be removed.

Reviewers: nemanjai, hfinkel, power-llvm-team, jsji, echristo, #powerpc, jhibbits

Reviewed By: hfinkel, jsji, jhibbits

Subscribers: hiraditya, shchenz, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70352
2019-11-25 14:26:08 -06:00
Nemanja Ivanovic 4d5c8caf9b [LLD] Add a default copy constructor to avoid warnings
This should fix the failure on the PPC64LE LLD bot.
2019-11-25 14:09:16 -06:00
Alexey Bataev bbc328c624 [OPENMP]Fix PR41826: symbols visibility in device code.
Summary:
Currently, we ignore all locality attributes/info when building for
the device and thus all symblos are externally visible and can be
preemted at the runtime. It may lead to incorrect results. We need to
follow the same logic, compiler uses for static/pie builds. But in some
cases changing of dso locality may lead to problems with codegen, so
instead mark external symbols as hidden instead in the device code.

Reviewers: jdoerfert

Subscribers: guansong, caomhin, kkwli0, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D70549
2019-11-25 15:01:28 -05:00
Tyker 7b86188b50 [Diagnostic] add a warning which warns about misleading indentation
Summary: Add a warning for misleading indentation similar to GCC's -Wmisleading-indentation

Reviewers: aaron.ballman, xbolva00

Reviewed By: aaron.ballman, xbolva00

Subscribers: arphaman, Ka-Ka, thakis

Differential Revision: https://reviews.llvm.org/D70638
2019-11-25 20:46:32 +01:00
Michał Górny 7644d8ba4d [lldb] [Process/NetBSD] Fix handling concurrent watchpoint events
Fix handling concurrent watchpoint events so that they are reported
correctly in LLDB.

If multiple watchpoints are hit concurrently, the NetBSD kernel reports
them as series of SIGTRAPs with a thread specified, and the debugger
investigates DR6 in order to establish which watchpoint was hit.  This
is normally fine.

However, LLDB disables and reenables the watchpoint on all threads after
each hit, which results in the hit status from DR6 being wiped.
As a result, it can't establish which watchpoint was hit in successive
SIGTRAP processing.

In order to workaround this problem, clear DR6 only if the breakpoint
is overwritten with a new one.  More specifically, move cleaning DR6
from ClearHardwareWatchpoint() to SetHardwareWatchpointWithIndex(),
and do that only if the newly requested watchpoint is different
from the one being set previously.  This ensures that the disable-enable
logic of LLDB does not clear watchpoint hit status for the remaining
threads.

This also involves refactoring of watchpoint logic.  With the old logic,
clearing watchpoint involved wiping dr6 & dr7, and setting it setting
dr{0..3} & dr7.  With the new logic, only enable bit is cleared
from dr7, and the remaining bits are cleared/overwritten while setting
new watchpoint.

Differential Revision: https://reviews.llvm.org/D70025
2019-11-25 20:11:59 +01:00
Michał Górny d970d4d4aa [lldb] [Process/NetBSD] Copy watchpoints to newly-created threads
NetBSD ptrace interface does not populate watchpoints to newly-created
threads.  Solve this via copying the watchpoints from the current thread
when new thread is reported via TRAP_LWP.

Add a test that verifies that when the user does not have permissions
to set watchpoints on NetBSD, the 'watchpoint set' errors out gracefully
and thread monitoring does not crash on being unable to copy watchpoints
to new threads.

Differential Revision: https://reviews.llvm.org/D70023
2019-11-25 20:11:59 +01:00
Michał Górny 8d9400b65b [lldb] [Process/NetBSD] Improve threading support
Implement major improvements to multithreaded program support.  Notably,
support tracking new and exited threads, associate signals and events
with correct threads and support controlling individual threads when
resuming.

Firstly, use PT_SET_EVENT_MASK to enable reporting of created and exited
threads via SIGTRAP.  Handle TRAP_LWP events to keep track
of the currently running threads.

Secondly, update the signal (both generic and SIGTRAP) handling code
to account for per-thread signals correctly.  Signals delivered
to the whole process are reported on all threads, while per-thread
signals and events are reported only to the specific thread.
The remaining threads are marked as 'stopped with no reason'.  Note that
NetBSD always stops all threads on debugger events.

Thirdly, implement the ability to set every thread as running, stopped
or single-stepping separately while continuing the process.  This also
provides the ability to send a signal to the whole process or to one
of its thread while resuming.

Differential Revision: https://reviews.llvm.org/D70022
2019-11-25 20:11:58 +01:00
Shoaib Meenai d018b556c7 [libcxx] Omit unneeded locale fallbacks on Android 21+
Android API level 21 and above have all these functions available, so we
don't need to include our fallback definitions.

Differential Revision: https://reviews.llvm.org/D69983
2019-11-25 11:06:08 -08:00
Michał Górny 6a7f6145d0 [lldb] [test] XFAIL ASAN tests on NetBSD 2019-11-25 20:03:41 +01:00
Craig Topper d6ec6e4bf6 [TargetLowering] Merge ExpandChainLibCall with makeLibCall
I need to be able to drop an operand for STRICT_FP_ROUND handling on X86. Merging these functions gives me the ArrayRef interface that passes the return type, operands, and debugloc instead of the Node.

Differential Revision: https://reviews.llvm.org/D70503
2019-11-25 10:52:49 -08:00
Sanjay Patel 35827164c4 [InstCombine] remove shuffle mask canonicalization that creates undef elements
This is NFC-intended because SimplifyDemandedVectorElts() does the same
transform later. As discussed in D70641, we may want to change that
behavior, so we need to isolate where it happens.
2019-11-25 13:33:56 -05:00
Dan Gohman 872a53ef94 [WebAssembly] Change the llvm-lto dir to use the LLVM Version
Using the version instead of the VCS revision, which isn't available
when LLVM_APPEND_VC_REV is set. The bitcode format should be
backwards-compatible at least within a minor version, so the version
string should be sufficient.

Differential Revision: https://reviews.llvm.org/D70677
2019-11-25 10:29:51 -08:00
Momchil Velikov 09555ce071 [ARM] Generate CMSE instructions from CMSE intrinsics
This patch adds instruction selection patterns for the TT, TTT, TTA, and TTAT
instructions and tests for llvm.arm.cmse.tt, llvm.arm.cmse.ttt,
llvm.arm.cmse.tta, and llvm.arm.cmse.ttat intrinsics (added in a previous
patch).

Patch by Javed Absar.

Differential Revision: https://reviews.llvm.org/D70407
2019-11-25 18:26:12 +00:00
Jonas Paulsson a7d3f6933d [SystemZ] Return the right offsets from getCalleeSavedSpillSlots().
// Due to the SystemZ ABI, the DWARF CFA (Canonical Frame Address) is not
// equal to the incoming stack pointer, but to incoming stack pointer plus
// 160.  The getOffsetOfLocalArea() returned value is interpreted as "the
// offset of the local area from the CFA".

The immediate offsets into the Register save area returned by
getCalleeSavedSpillSlots() should take this offset into account, which this
patch makes sure of.

Patch and review by Ulrich Weigand.
https://reviews.llvm.org/D70427
2019-11-25 19:03:05 +01:00
Whitney Tsang aaf7f05a96 [NFC][LoopFusion] Use isControlFlowEquivalent() from CodeMoverUtils.
Reviewer: kbarton, jdoerfert, Meinersbur, bmahjour, etiotto
Reviewed By: Meinersbur
Subscribers: hiraditya, llvm-commits
Tag: LLVM
Differential Revision: https://reviews.llvm.org/D70619
2019-11-25 17:54:42 +00:00
Nemanja Ivanovic 7fbaa8097e [PowerPC] Fix VSX clobbers of CSR registers
If an inline asm statement clobbers a VSX register that overlaps with a
callee-saved Altivec register or FPR, we will not record the clobber and will
therefore violate the ABI. This is clearly a bug so this patch fixes it.

Differential revision: https://reviews.llvm.org/D68576
2019-11-25 11:41:34 -06:00
Sanjay Patel e85d2e4981 [InstCombine] prevent infinite loop from conflicting shuffle mask transforms
The pattern in question is currently not possible because we
aggressively (wrongly) transform mask elements to undef values
if they choose from an undef operand. That, however, would
change if we tighten our semantics for shuffles as discussed
in D70641. Adding this check gives us the flexibility to make
that change with minimal overhead for current definitions.
2019-11-25 12:00:41 -05:00
Kostya Kortchinsky 15664fe2c4 [scudo][standalone] Fix for releaseToOS prior to init
Summary:
cferris@ found an issue where calling `releaseToOS` prior to any other
heap operation would lead to a crash, due to the allocator not being
properly initialized (it was discovered via `mallopt`).

The fix is to call `initThreadMaybe` prior to calling `releaseToOS` for
the Primary.

Add a test that crashes prior to fix.

Reviewers: hctim, cferris, pcc, eugenis

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D70552
2019-11-25 08:38:45 -08:00
bmahjour bec37c3fc7 [DDG] Data Dependence Graph - Topological Sort
Summary:
In this patch the DDG DAG is sorted topologically to put the
nodes in the graph in the order that would satisfy all
dependencies. This helps transformations that would like to
generate code based on the DDG. Since the DDG is a DAG a
reverse-post-order traversal would give us the topological
ordering. This patch also sorts the basic blocks passed to
the builder based on program order to ensure that the
dependencies are computed in the correct direction.

Authored By: bmahjour

Reviewer: Meinersbur, fhahn, myhsu, xtian, dmgreen, kbarton, jdoerfert

Reviewed By: Meinersbur

Subscribers: ychen, arphaman, simoll, a.elovikov, mgorny, hiraditya, jfb, wuzish, llvm-commits, jsji, Whitney, etiotto, ppc-slack

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70609
2019-11-25 11:28:58 -05:00
Sanjay Patel fc31b58eff [InstCombine] simplify code for shuffle mask canonicalization; NFC
We never use the local 'Mask' before returning, so that was dead code.
2019-11-25 11:11:12 -05:00
Sanjay Patel 847aabf11f [InstCombine] remove dead code from shuffle mask canonicalization; NFC 2019-11-25 10:54:18 -05:00
Sanjay Patel 20684092ab [InstCombine] simplify loop for shuffle mask canonicalization; NFC 2019-11-25 10:41:50 -05:00
Hans Wennborg 21f26470e9 Revert 3f91705ca5 "ARM-NEON: make type modifiers orthogonal and allow multiple modifiers."
This broke the vcreate_u64 intrinsic. Example:

  $ cat /tmp/a.cc
  #include <arm_neon.h>

  void g() {
    auto v = vcreate_u64(0);
  }
  $ bin/clang -c /tmp/a.cc --target=arm-linux-androideabi16 -march=armv7-a
  /tmp/a.cc:4:12: error: C-style cast from scalar 'int' to vector 'uint64x1_t' (vector of 1 'uint64_t' value) of different size
    auto v = vcreate_u64(0);
             ^~~~~~~~~~~~~~
  /work/llvm.monorepo/build.release/lib/clang/10.0.0/include/arm_neon.h:4144:11: note: expanded from macro 'vcreate_u64'
    __ret = (uint64x1_t)(__p0); \
            ^~~~~~~~~~~~~~~~~~

Reverting until this can be investigated.

> The modifier system used to mutate types on NEON intrinsic definitions had a
> separate letter for all kinds of transformations that might be needed, and we
> were quite quickly running out of letters to use. This patch converts to a much
> smaller set of orthogonal modifiers that can be applied together to achieve the
> desired effect.
>
> When merging with downstream it is likely to cause a conflict with any local
> modifications to the .td files. There is a new script in
> utils/convert_arm_neon.py that was used to convert all .td definitions and I
> would suggest running it on the last downstream version of those files before
> this commit rather than resolving conflicts manually.
2019-11-25 16:27:53 +01:00
Jay Foad 357bd914a1 [AMDGPU] Fix function name in debug output 2019-11-25 15:22:04 +00:00
jasonliu 906ecae2ed [AIX][XCOFF] Generate undefined symbol in symbol table for external function call
Summary:
This patch sets up the infrastructure for

 1. Associate MCSymbolXCOFF with an MCSectionXCOFF when it could not
    get implicitly associated.
 2. Generate undefined symbols. The patch itself generates undefined symbol
    for external function call only. Generate undefined symbol for external
    global variable and external function descriptors will be handled in
    separate patch(s) after this is land.

Differential Revision: https://reviews.llvm.org/D70443
2019-11-25 15:02:01 +00:00
Raphael Isemann d1782133d9 [lldb][NFC] Allow range-based for-loops on VariableList
Summary:
Adds support for doing range-based for-loops on LLDB's VariableList and
modernises all the index-based for-loops in LLDB where possible.

Reviewers: labath, jdoerfert

Reviewed By: labath

Subscribers: JDevlieghere, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D70668
2019-11-25 15:03:46 +01:00
Jeremy Morse d9c9a4e48d [DebugInfo] Avoid register coalesing unsoundly changing DBG_VALUE locations
This is a re-land of D56151 / r364515 with a completely new implementation.

Once MIR code leaves SSA form and the liveness of a vreg is considered,
DBG_VALUE insts are able to refer to non-live vregs, because their
debug-uses do not contribute to liveness. This non-liveness becomes
problematic for optimizations like register coalescing, as they can't
``see'' the debug uses in the liveness analyses.

As a result registers get coalesced regardless of debug uses, and that can
lead to invalid variable locations containing unexpected values. In the
added test case, the first vreg operand of ADD32rr is merged with various
copies of the vreg (great for performance), but a DBG_VALUE of the
unmodified operand is blindly updated to the modified operand. This changes
what value the variable will appear to have in a debugger.

Fix this by changing any DBG_VALUE whose operand will be resurrected by
register coalescing to be a $noreg DBG_VALUE, i.e. give the variable no
location. This is an overapproximation as some coalesced locations are safe
(others are not) -- an extra domination analysis would be required to work
out which, and it would be better if we just don't generate non-live
DBG_VALUEs.

Differential Revision: https://reviews.llvm.org/D64630
2019-11-25 13:47:06 +00:00