Commit Graph

47 Commits

Author SHA1 Message Date
Rafael Espindola 14fde14ca1 Don't call exit from cl::PrintHelpMessage.
Most callers were not expecting the exit(0) and trying to exit with a
different value.

This also adds back the call to cl::PrintHelpMessage in llvm-ar.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312761 91177308-0d34-0410-b5e6-96231b3b80d8
2017-09-07 23:30:48 +00:00
Keith Wyss 013a4d7319 [XRay][tools] Function call stack based analysis tooling for XRay traces
Second try after fixing a code san problem with iterator reference types.

This change introduces a subcommand to the llvm-xray tool called
"stacks" which allows for analysing XRay traces provided as inputs and
accounting time to stacks instead of just individual functions. This
gives us a more precise view of where in a program the latency is
actually attributed.

The tool uses a trie data structure to keep track of the caller-callee
relationships as we process the XRay traces. In particular, we keep
track of the function call stack as we enter functions. While we're
doing this we're adding nodes in a trie and indicating a "calls"
relatinship between the caller (current top of the stack) and the callee
(the new top of the stack). When we push function ids onto the stack, we
keep track of the timestamp (TSC) for the enter event.

When exiting functions, we are able to account the duration by getting
the difference between the timestamp of the exit event and the
corresponding entry event in the stack. This works even if we somehow
miss the exit events for intermediary functions (i.e. if the exit event
is not cleanly associated with the enter event at the top of the stack).

The output of the tool currently provides just the top N leaf functions
that contribute the most latency, and the top N stacks that have the
most frequency. In the future we can provide more sophisticated query
mechanisms and potentially an export to database feature to make offline
analysis of the stack traces possible with existing tools.

Differential revision: D34863

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312733 91177308-0d34-0410-b5e6-96231b3b80d8
2017-09-07 18:07:48 +00:00
Keith Wyss 0ef1731fbc Revert "[XRay][tools] Function call stack based analysis tooling for XRay traces"
This reverts commit 204a65e0702847a1880336372ad7abd1df414b44.

Double ref qualifier failed bots.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312428 91177308-0d34-0410-b5e6-96231b3b80d8
2017-09-03 00:40:13 +00:00
Keith Wyss b01acdaefa [XRay][tools] Function call stack based analysis tooling for XRay traces
This change introduces a subcommand to the llvm-xray tool called
"stacks" which allows for analysing XRay traces provided as inputs and
accounting time to stacks instead of just individual functions. This
gives us a more precise view of where in a program the latency is
actually attributed.

The tool uses a trie data structure to keep track of the caller-callee
relationships as we process the XRay traces. In particular, we keep
track of the function call stack as we enter functions. While we're
doing this we're adding nodes in a trie and indicating a "calls"
relatinship between the caller (current top of the stack) and the callee
(the new top of the stack). When we push function ids onto the stack, we
keep track of the timestamp (TSC) for the enter event.

When exiting functions, we are able to account the duration by getting
the difference between the timestamp of the exit event and the
corresponding entry event in the stack. This works even if we somehow
miss the exit events for intermediary functions (i.e. if the exit event
is not cleanly associated with the enter event at the top of the stack).

The output of the tool currently provides just the top N leaf functions
that contribute the most latency, and the top N stacks that have the
most frequency. In the future we can provide more sophisticated query
mechanisms and potentially an export to database feature to make offline
analysis of the stack traces possible with existing tools.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312426 91177308-0d34-0410-b5e6-96231b3b80d8
2017-09-03 00:03:47 +00:00
Dean Michael Berris 72cfebd887 [XRay][tools] Fix an accounting bug in llvm-xray account
Summary:
Before this patch, llvm-xray account will assume that thread stacks will
not be empty. Unfortunately there are cases where an instrumented
function will see a call to `fork()` which will cause the child process
to not see the start of the function, but only see the end of the
function. The tooling cannot assume that threads will always have
perfect stacks, and so we change it to support this reality.

Reviewers: dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31870

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312204 91177308-0d34-0410-b5e6-96231b3b80d8
2017-08-31 01:07:24 +00:00
Zachary Turner 19ca2b0f9d Move Object format code to lib/BinaryFormat.
This creates a new library called BinaryFormat that has all of
the headers from llvm/Support containing structure and layout
definitions for various types of binary formats like dwarf, coff,
elf, etc as well as the code for identifying a file from its
magic.

Differential Revision: https://reviews.llvm.org/D33843

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304864 91177308-0d34-0410-b5e6-96231b3b80d8
2017-06-07 03:48:56 +00:00
Dean Michael Berris 123fc0d45e [XRay][tools] Remove wayward semicolon (NFC)
Follow-up to D29320.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301378 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-26 03:49:49 +00:00
Dean Michael Berris 8577a8c0fd [XRay][tools] Fixup definition for stat division.
Copy-pasta error.

Follow-up to D29320.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301376 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-26 01:35:23 +00:00
Dean Michael Berris 0d479b0056 [XRay][tools] Fixup for pedantic and permissive errors/warnings
Remove extraneous semicolons and fully qualify the Trace type.

Follow-up to D29320.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301161 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-24 06:15:53 +00:00
Dean Michael Berris ae0fbfb1fb [XRay] A tool for Comparing xray function call graphs
Summary:
This is a tool for comparing the function graphs produced by the
llvm-xray graph too. It takes the form of a new subcommand of the
llvm-xray tool 'graph-diff'.

This initial version of the patch is very rough, but it is close to
feature complete.

Depends on D29363

Reviewers: dblaikie, dberris

Reviewed By: dberris

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D29320

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301160 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-24 05:54:33 +00:00
Dean Michael Berris 44292db890 [XRay][tools] Add option to llvm-xray extract to symbolize functions
Summary:
This allows us to, if the symbol names are available in the binary, be
able to provide the function name in the YAML output.

Reviewers: dblaikie, pelikan

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32153

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300624 91177308-0d34-0410-b5e6-96231b3b80d8
2017-04-18 23:23:54 +00:00
Dean Michael Berris 365612c08f [XRay][tools] Remove some assertions in llvm-xray graph
Summary:
Assertions assuming that function calls may not have zero durations do
not seem to hold in the wild. There are valid cases where the conversion
of the tsc counters end up becoming zero-length durations. These
assertions don't really hold and the algorithms don't need those to be
true for them to work.

Reviewers: dblaikie, echristo

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31519

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299150 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-31 01:56:45 +00:00
Dean Michael Berris 8985450e52 [XRay][tools] Handle "no subcommand" case for llvm-xray
Summary:
Currently the llvm-xray commandline tool fails to handle the case for
when no subcommand is provided in a graceful manner. This fixes that to
print the help message explaining the subcommands and the available
options.

Reviewers: pcc, pelikan

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D31409

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298975 91177308-0d34-0410-b5e6-96231b3b80d8
2017-03-29 04:55:45 +00:00
Dean Michael Berris de5a65f30a [XRAY] A Color Choosing helper for XRay Graph
Summary:
In Preparation for graph comparison, this patch breaks out the color
choice code from xray-graph into a library and adds polynomials for
the Sequential and Difference sets from ColorBrewer.

Depends on D29005

Reviewers: dblaikie, chandlerc, dberris

Reviewed By: dberris

Subscribers: chandlerc, llvm-commits, mgorny

Differential Revision: https://reviews.llvm.org/D29363

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@296210 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-25 00:26:42 +00:00
Dean Michael Berris 73d4ebd620 [XRAY] [x86_64] Adding a Flight Data filetype reader to the llvm-xray Trace implementation.
Summary:
The file type packs function trace data onto disk from potentially multiple
threads that are aggregated and flushed during the course of an instrumented
program's runtime.

It is named FDR mode or Flight Data recorder as an analogy to plane
blackboxes, which instrument a running system without access to IO.

The writer code is defined in compiler-rt in xray_fdr_logging.h/cc

Reviewers: rSerge, kcc, dberris

Reviewed By: dberris

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29697

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295397 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-17 01:47:16 +00:00
Dimitry Andric 193dc0bf84 Disable wrapping llvm-xray YAML output
Summary:
The YAML output produced by llvm-xray is supposed to be wrapped at the
arbitrary default of 70 columns set by `yaml:Output`.  Unfortunately,
the wrapping is rather unpredictable, and can easily go past the set
number of columns, depending on the execution environment.

To make the YAML output environment-independent, disable wrapping
instead.

Reviewers: dberris

Reviewed By: dberris

Subscribers: fhahn, llvm-commits

Differential Revision: https://reviews.llvm.org/D29962

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295116 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-14 22:49:49 +00:00
Dean Michael Berris 4dc48bfbbe [XRay] A graph Class for the llvm-xray graph
Summary:
In preparation for graph comparison and filtering, this is a library for
representing graphs in LLVM. This will enable easier encapsulation and reuse
of graphs in llvm-xray.

Depends on D28999, D28225

Reviewers: dblaikie, dberris

Reviewed By: dberris

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D29005

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294717 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-10 06:36:08 +00:00
Dean Michael Berris a8b5e78a13 Revert "[XRay] A graph Class for the llvm-xray graph"
Broke tests, reverting.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294714 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-10 06:05:46 +00:00
Dean Michael Berris f3a1b3c336 [XRay] A graph Class for the llvm-xray graph
Summary:
In preparation for graph comparison and filtering, this is a library for
representing graphs in LLVM. This will enable easier encapsulation and reuse
of graphs in llvm-xray.

Depends on D28999, D28225

Reviewers: dblaikie, dberris

Reviewed By: dberris

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D29005

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294713 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-10 05:40:37 +00:00
Dean Michael Berris dd336006bd [XRay] Use std::errc::invalid_argument instead of std::errc::bad_message
This change should appease the mingw32 builds.

Follow-up to D29319.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293725 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-01 00:22:20 +00:00
Dean Michael Berris 93789c8851 [XRay] Define the InstrumentationMap type
Summary:
This change implements the instrumentation map loading library which can
understand both YAML-defined instrumentation maps, and ELF 64-bit object
files that have the XRay instrumentation map section. We break it out
into a library on its own to allow for other applications to deal with
the XRay instrumentation map defined in XRay-instrumented binaries.

This type provides both raw access to the logical representation of the
instrumentation map entries as well as higher level functions for
converting a function ID into a function address.

At this point we only support ELF64 binaries and YAML-defined XRay
instrumentation maps. Future changes should extend this to support
32-bit ELF binaries, as well as other binary formats (like MachO).

As part of this change we also migrate all uses of the extraction logic
that used to be defined in tools/llvm-xray/ to use this new type and
interface for loading from files. We also remove the flag from the
`llvm-xray` tool that required users to specify the type of the
instrumentation map file being provided to instead make the library
auto-detect the file type.

Reviewers: dblaikie

Subscribers: mgorny, varno, llvm-commits

Differential Revision: https://reviews.llvm.org/D29319

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293721 91177308-0d34-0410-b5e6-96231b3b80d8
2017-02-01 00:05:29 +00:00
Sylvestre Ledru bd96ea7b6a Remove unused 'using' declaration. Found by clang-tidy: misc-unused-using-decls NFC
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293382 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-28 13:42:54 +00:00
Dean Michael Berris 420c0701f8 Implemented color coding and Vertex labels in XRay Graph
Summary:
A patch to enable the llvm-xray graph subcommand to color edges and
vertices based on statistics and to annotate vertices with statistics.

Depends on D27243

Reviewers: dblaikie, dberris

Reviewed By: dberris

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D28225

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293031 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-25 07:14:43 +00:00
Pavel Labath c52f4a4684 Remove pid_t usage from llvm-xray
This type is not available on windows.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292206 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-17 09:39:31 +00:00
David Blaikie 1854d25176 Add missing header to see if that clears up the build
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292166 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-16 21:40:08 +00:00
David Blaikie aab72f0669 Attempt to fix the MSVC build by using llvm::errc instead of std::errc
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292163 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-16 21:20:51 +00:00
David Blaikie 061ca191c0 [XRay] Implement the llvm-xray graph subcommand
Here we define the `graph` subcommand which generates a graph from the function
call information and uses it to present the call information graphically with
additional annotations.

Reviewers: dblaikie, dberris

Differential Revision: https://reviews.llvm.org/D27243

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292156 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-16 20:36:26 +00:00
Pavel Labath 8a1006b50d [llvm-xray] Fix android build
std::to_string is not available in the android ndk. Using llvm::to_string
instead.

Committing as obvious.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292143 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-16 16:38:23 +00:00
NAKAMURA Takumi bda0ff2479 xray-account: Avoid std::errc::bad_message to appease mingw.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291863 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-13 00:17:15 +00:00
Hans Wennborg fa3329aff5 Avoid std::errc::protocol_* to appease mingw
Like r291636 and r285261.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291786 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-12 18:33:14 +00:00
Simon Pilgrim e821446fbc Fix windows buildbots building llvm-xray
2 issues:
1 - replaced unix-style pid_t with cross-platform llvm::sys::ProcessInfo::ProcessId 
2 - fixed shadow variable warning in lambda expression

Reviewed by @filcab

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291760 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-12 11:13:51 +00:00
Dean Michael Berris 182166ec7e [XRay] Include <numeric> for std::accumulate.
Fix-up following D24377.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291750 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-12 07:43:54 +00:00
Dean Michael Berris c4416a6dc0 [XRay] Implement the llvm-xray account subcommand
Summary:
This is the third of a multi-part change to implement subcommands for
the `llvm-xray` tool.

Here we define the `account` subcommand which does simple function call
accounting, generating basic statistics on function calls we find in an
XRay log/trace. We support text output and csv output for this
subcommand.

This change also supports sorting, summing, and filtering the top N
results.

Part of this tool will later be turned into a library that could be used
for basic function call accounting.

Depends on D24376.

Reviewers: dblaikie, echristo

Subscribers: mehdi_amini, dberris, beanz, llvm-commits

Differential Revision: https://reviews.llvm.org/D24377

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291749 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-12 07:38:13 +00:00
Dean Michael Berris 14cdbca6b8 [XRay] Define the library for XRay trace logs
Summary:
In this change we move the definition of the log reading routines from
the tools directory in LLVM to {include/llvm,lib}/XRay. We improve the
documentation a little bit for the publicly accessible headers, and
adjust the top-matter. This also leads to some refactoring and cleanup
in the tooling code.

In particular, we do the following:

  - Rename the class from LogReader to Trace, as it better represents
    the logical set of records as opposed to a log.
  - Use file type detection instead of asking the user to say what
    format the input file is. This allows us to keep the interface
    simple and encapsulate the logic of loading the data appropriately.

In future changes we increase the API surface and write dedicated unit
tests for the XRay library.

Depends on D24376.

Reviewers: dblaikie, echristo

Subscribers: mehdi_amini, mgorny, llvm-commits, varno

Differential Revision: https://reviews.llvm.org/D28345

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291652 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-11 06:39:09 +00:00
NAKAMURA Takumi 91424c3023 tools/llvm-xray: Avoid std::errc::protocol_* to appease mingw, like r285261.
They are oriented from winsock and mingw doesn't import them.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291636 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-11 01:06:57 +00:00
Dean Michael Berris 5165d0d2b3 [XRay] Fixup includes for modules build
Remove unnecessary system header include.

Follow-up to D24376.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291533 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-10 03:21:54 +00:00
Dean Michael Berris 5b82745386 [XRay] Don't include <unistd.h> unnecessarily
Follow-up to D24376.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291531 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-10 02:51:13 +00:00
Dean Michael Berris 6e1f066adf [XRay] Implement llvm-xray convert -- trace file conversion
This is the second part of a multi-part change to define additional
subcommands to the `llvm-xray` tool.

This change defines a conversion subcommand to take XRay log files, and
turns them from one format to another (binary or YAML). This currently
only supports the first version of the log file format, defined in the
compiler-rt runtime.

Depends on D21987.

Reviewers: dblaikie, echristo

Subscribers: mehdi_amini, dberris, beanz, llvm-commits

Differential Revision: https://reviews.llvm.org/D24376

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291529 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-10 02:38:11 +00:00
Mehdi Amini df0b8bce48 Make the Error class constructor protected
This is forcing to use Error::success(), which is in a wide majority
of cases a lot more readable.

Differential Revision: https://reviews.llvm.org/D26481

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@286561 91177308-0d34-0410-b5e6-96231b3b80d8
2016-11-11 04:28:40 +00:00
NAKAMURA Takumi eb87cccbef xray-extract.cc: Quick fix for mingw, to avoid errc::protocol_error.
errc::protocol_error is winsock-oriented and mingw doesn't include it. (MS does, though)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285261 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-27 00:34:24 +00:00
Dean Michael Berris 83f97dc820 [XRay] Remove unnecessary include of <unistd.h>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285171 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-26 04:46:50 +00:00
Dean Michael Berris 1af0e79b75 [XRay] Remove unnecessary include of <unistd.h>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285170 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-26 04:36:31 +00:00
Dean Michael Berris dbc97f38e7 [XRay] Move specialisations into correct namespace
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285168 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-26 04:26:53 +00:00
Dean Michael Berris 07792fbd6c [XRay] Remove extra ; to make -wpedantic happy
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285167 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-26 04:21:17 +00:00
Dean Michael Berris 5a35548822 [XRay] Implement llvm-xray extract, start of the llvm-xray tool
Usage:

  llvm-xray extract <object file> [-o <filename or '-'>]

The tool gets the XRay instrumentation map from an object file and turns
it into YAML.  We first support ELF64 sleds on x86_64 binaries, with
provision for supporting other supported platforms and formats later.

This is the first of a many-part change to fully implement the
`llvm-xray` tool.

We also define a subcommand registration and dispatch mechanism to be
used by other further subcommand implementations for llvm-xray.

Diffusion Revision: https://reviews.llvm.org/D21987

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285165 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-26 04:14:34 +00:00
Dean Michael Berris e9512859ea Revert "[XRay] Implement llvm-xray extract, start of the llvm-xray tool"
Reverts r285155 -- misconfigured tests.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285156 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-26 01:50:59 +00:00
Dean Michael Berris 433938ad4c [XRay] Implement llvm-xray extract, start of the llvm-xray tool
Usage:

  llvm-xray extract <object file> [-o <filename or '-'>]

The tool gets the XRay instrumentation map from an object file and turns
it into YAML.  We first support ELF64 sleds on x86_64 binaries, with
provision for supporting other supported platforms and formats later.

This is the first of a many-part change to fully implement the
`llvm-xray` tool.

We also define a subcommand registration and dispatch mechanism to be
used by other further subcommand implementations for llvm-xray.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@285155 91177308-0d34-0410-b5e6-96231b3b80d8
2016-10-26 01:42:59 +00:00