Revert "[DebugInfo] Add DWARF emission for DBG_VALUE_LIST"

This reverts commit 0da27ba56c9f5e3f534a65401962301189eac342.

This revision was causing an error on the sanitizer-x86_64-linux-autoconf bu

Revert "[DebugInfo] Add DWARF emission for DBG_VALUE_LIST"

This reverts commit 0da27ba56c9f5e3f534a65401962301189eac342.

This revision was causing an error on the sanitizer-x86_64-linux-autoconf build.

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[DebugInfo] Add DWARF emission for DBG_VALUE_LIST

This patch allows DBG_VALUE_LIST instructions to be emitted to DWARF with valid
DW_AT_locations. This change mainly affects DbgEntityHistoryCalculat

[DebugInfo] Add DWARF emission for DBG_VALUE_LIST

This patch allows DBG_VALUE_LIST instructions to be emitted to DWARF with valid
DW_AT_locations. This change mainly affects DbgEntityHistoryCalculator, which
now tracks multiple registers per value, and DwarfDebug+DwarfExpression, which
can now emit multiple machine locations as part of a DWARF expression.

Differential Revision: https://reviews.llvm.org/D83495

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make the AsmPrinterHandler array public

This lets external consumers customize the output, similar to how
AssemblyAnnotationWriter lets the caller define callbacks when printing
IR. The array of han

make the AsmPrinterHandler array public

This lets external consumers customize the output, similar to how
AssemblyAnnotationWriter lets the caller define callbacks when printing
IR. The array of handlers already existed, this just cleans up the code
so that it can be exposed publically.

Replaces https://reviews.llvm.org/D74158

Differential Revision: https://reviews.llvm.org/D89613

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Recommit "[CodeView] Emit static data members as S_CONSTANTs."

We used to only emit static const data members in CodeView as
S_CONSTANTS when they were used; this patch makes it so they are always e

Recommit "[CodeView] Emit static data members as S_CONSTANTs."

We used to only emit static const data members in CodeView as
S_CONSTANTS when they were used; this patch makes it so they are always emitted.

This changes CodeViewDebug.cpp to find the static const members from the
class debug info instead of creating DIGlobalVariables in the IR
whenever a static const data member is used.

Bug: https://bugs.llvm.org/show_bug.cgi?id=47580

Differential Revision: https://reviews.llvm.org/D89072

This reverts commit 504615353f31136dd6bf7a971b6c236fd70582be.

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Revert "make the AsmPrinterHandler array public"

I messed up one of the tests.

make the AsmPrinterHandler array public

This lets external consumers customize the output, similar to how
AssemblyAnnotationWriter lets the caller define callbacks when printing
IR. The array of han

make the AsmPrinterHandler array public

This lets external consumers customize the output, similar to how
AssemblyAnnotationWriter lets the caller define callbacks when printing
IR. The array of handlers already existed, this just cleans up the code
so that it can be exposed publically.

Differential Revision: https://reviews.llvm.org/D74158

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Temporary fix for D85085 debug_loc bug with basic block sections.

Until then, this one line fix removes the assert fail with basic block sections
with debug info. Bug tracking this: #47549
This fix

Temporary fix for D85085 debug_loc bug with basic block sections.

Until then, this one line fix removes the assert fail with basic block sections
with debug info. Bug tracking this: #47549
This fix does not generate loc list or DW_AT_const_value if the argument is
mentioned in a different section than the start of the function.

Temporarily fixes bugzilla : https://bugs.llvm.org/show_bug.cgi?id=47549

Differential Revision: https://reviews.llvm.org/D87787

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[DwarfDebug] Improve single location detection in validThroughout (2/4)

With this patch we're now accounting for two more cases which should be
considered 'valid throughout': First, where RangeEnd i

[DwarfDebug] Improve single location detection in validThroughout (2/4)

With this patch we're now accounting for two more cases which should be
considered 'valid throughout': First, where RangeEnd is ScopeEnd. Second, where
RangeEnd comes before ScopeEnd when including meta instructions, but are both
preceded by the same non-meta instruction.

CTMark shows a geomean binary size reduction of 1.5% for RelWithDebInfo builds.
`llvm-locstats` (using D85636) shows a very small variable location coverage
change in 2 of 10 binaries, but it is in the order of 10s of bytes which lines
up with my expectations.

I've added a test which checks both of these new cases. The first check in the
test isn't strictly necessary for this patch. But I'm not sure that it is
explicitly tested anywhere else, and is useful for the final patch in the
series.

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D86151

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Revert rG5dd566b7c7b78bd- "PassManager.h - remove unnecessary Function.h/Module.h includes. NFCI."

This reverts commit 5dd566b7c7b78bd385418c72d63c79895be9ae97.

Causing some buildbot failures that

Revert rG5dd566b7c7b78bd- "PassManager.h - remove unnecessary Function.h/Module.h includes. NFCI."

This reverts commit 5dd566b7c7b78bd385418c72d63c79895be9ae97.

Causing some buildbot failures that I'm not seeing on MSVC builds.

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PassManager.h - remove unnecessary Function.h/Module.h includes. NFCI.

PassManager.h is one of the top headers in the ClangBuildAnalyzer frontend worst offenders list.

This exposes a large number o

PassManager.h - remove unnecessary Function.h/Module.h includes. NFCI.

PassManager.h is one of the top headers in the ClangBuildAnalyzer frontend worst offenders list.

This exposes a large number of implicit dependencies on various forward declarations/includes in other headers that need addressing.

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[DebugInfo] Drop location ranges for variables which exist entirely outside the variable's scope

Summary:
This patch reduces file size in debug builds by dropping variable locations a
debugger user

[DebugInfo] Drop location ranges for variables which exist entirely outside the variable's scope

Summary:
This patch reduces file size in debug builds by dropping variable locations a
debugger user will not see.

After building the debug entity history map we loop through it. For each
variable we look at each entry. If the entry opens a location range which does
not intersect any of the variable's scope's ranges then we mark it for removal.
After visiting the entries for each variable we also mark any clobbering
entries which will no longer be referenced for removal, and then finally erase
the marked entries. This all requires the ability to query the order of
instructions, so before this runs we number them.

Tests:
Added llvm/test/DebugInfo/X86/trim-var-locs.mir

Modified llvm/test/DebugInfo/COFF/register-variables.ll
Branch folding merges the tails of if.then and if.else into if.else. Each
blocks' debug-locations point to different scopes so when they're merged we
can't use either. Because of this the variable 'c' ends up with a location
range which doesn't cover any instructions in its scope; with the patch
applied the location range is dropped and its flag changes to IsOptimizedOut.

Modified llvm/test/DebugInfo/X86/live-debug-variables.ll
Modified llvm/test/DebugInfo/ARM/PR26163.ll
In both tests an out of scope location is now removed. The remaining location
covers the entire scope of the variable allowing us to emit it as a single
location.

Reviewed By: aprantl

Differential Revision: https://reviews.llvm.org/D82129

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This patch adds basic debug info support with basic block sections.

This patch uses ranges for debug information when a function contains basic block sections rather than using [lowpc, highpc]. This

This patch adds basic debug info support with basic block sections.

This patch uses ranges for debug information when a function contains basic block sections rather than using [lowpc, highpc]. This is also the first in a series of patches for debug info and does not contain the support for linker relaxation. That will be done as a follow up patch.

Differential Revision: https://reviews.llvm.org/D78851

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[DebugInfo] Update MachineInstr to help support variadic DBG_VALUE instructions

Following on from this RFC[0] from a while back, this is the first patch towards
implementing variadic debug values.

[DebugInfo] Update MachineInstr to help support variadic DBG_VALUE instructions

Following on from this RFC[0] from a while back, this is the first patch towards
implementing variadic debug values.

This patch specifically adds a set of functions to MachineInstr for performing
operations specific to debug values, and replacing uses of the more general
functions where appropriate. The most prevalent of these is replacing
getOperand(0) with getDebugOperand(0) for debug-value-specific code, as the
operands corresponding to values will no longer be at index 0, but index 2 and
upwards: getDebugOperand(x) == getOperand(x+2). Similar replacements have been
added for the other operands, along with some helper functions to replace
oft-repeated code and operate on a variable number of value operands.

[0] http://lists.llvm.org/pipermail/llvm-dev/2020-February/139376.html<Paste>

Differential Revision: https://reviews.llvm.org/D81852

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[MC] De-capitalize another set of MCStreamer::Emit* functions

Emit{ValueTo,Code}Alignment Emit{DTP,TP,GP}* EmitSymbolValue etc

[DWARF] Emit DW_AT_call_return_pc as an address

This reverts D53469, which changed llvm's DWARF emission to emit
DW_AT_call_return_pc as a function-local offset. Such an encoding is not
compatible w

[DWARF] Emit DW_AT_call_return_pc as an address

This reverts D53469, which changed llvm's DWARF emission to emit
DW_AT_call_return_pc as a function-local offset. Such an encoding is not
compatible with post-link block re-ordering tools and isn't standards-
compliant.

In addition to reverting back to the original DW_AT_call_return_pc
encoding, teach lldb how to fix up DW_AT_call_return_pc when the address
comes from an object file pointed-to by a debug map. While doing this I
noticed that lldb's support for tail calls that cross a DSO/object file
boundary wasn't covered, so I added tests for that. This latter case
exercises the newly added return PC fixup.

The dsymutil changes in this patch were originally included in D49887:
the associated test should be sufficient to test DW_AT_call_return_pc
encoding purely on the llvm side.

Differential Revision: https://reviews.llvm.org/D72489

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Stop undef fragments from closing non-overlapping fragments

Summary:
When DwarfDebug::buildLocationList() encountered an undef debug value,
it would truncate all open values, regardless if they were

Stop undef fragments from closing non-overlapping fragments

Summary:
When DwarfDebug::buildLocationList() encountered an undef debug value,
it would truncate all open values, regardless if they were overlapping or
not. This patch fixes so that it only does that for overlapping fragments.

This change unearthed a bug that I had introduced in D57511,
which I have fixed in this patch. The code in DebugHandlerBase that
changes labels for parameter debug values could break DwarfDebug's
assumption that the labels for the entries in the debug value history
are monotonically increasing. Before this patch, that bug could result
in location list entries whose ending address was lower than the
beginning address, and with the changes for undef debug values that this
patch introduces it could trigger an assertion, due to attempting to
emit location list entries with empty ranges. A reproducer for the bug
is added in param-reg-const-mix.mir.

Reviewers: aprantl, jmorse, probinson

Reviewed By: aprantl

Subscribers: javed.absar, llvm-commits

Tags: #debug-info, #llvm

Differential Revision: https://reviews.llvm.org/D62379

llvm-svn: 361820

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[DebugInfo] Delete TypedDINodeRef

TypedDINodeRef<T> is a redundant wrapper of Metadata * that is actually a T *.

Accordingly, change DI{Node,Scope,Type}Ref uses to DI{Node,Scope,Type} * or their co

[DebugInfo] Delete TypedDINodeRef

TypedDINodeRef<T> is a redundant wrapper of Metadata * that is actually a T *.

Accordingly, change DI{Node,Scope,Type}Ref uses to DI{Node,Scope,Type} * or their const variants.
This allows us to delete many resolve() calls that clutter the code.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D61369

llvm-svn: 360108

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[DebugInfo] Improve handling of clobbered fragments

Summary:
Currently the DbgValueHistorymap only keeps track of clobbered registers
for the last debug value that it has encountered. This could lea

[DebugInfo] Improve handling of clobbered fragments

Summary:
Currently the DbgValueHistorymap only keeps track of clobbered registers
for the last debug value that it has encountered. This could lead to
preceding register-described debug values living on longer in the
location lists than they should. See PR40283 for an example. This
patch does not introduce tracking of multiple registers, but changes
the DbgValueHistoryMap structure to allow for that in a follow-up
patch. This patch is not NFC, as it at least fixes two bugs in
DwarfDebug (both are covered in the new clobbered-fragments.mir test):

* If a debug value was clobbered (its End pointer set), the value would
still be added to OpenRanges, meaning that the succeeding location list
entries could potentially contain stale values.

* If a debug value was clobbered, and there were non-overlapping
fragments that were still live after the clobbering, DwarfDebug would
not create a location list entry starting directly after the
clobbering instruction. This meant that the location list could have
a gap until the next debug value for the variable was encountered.

Before this patch, the history map was represented by <Begin, End>
pairs, where a new pair was created for each new debug value. When
dealing with partially overlapping register-described debug values, such
as in the following example:

DBG_VALUE $reg2, $noreg, !1, !DIExpression(DW_OP_LLVM_fragment, 32, 32)
[...]
DBG_VALUE $reg3, $noreg, !1, !DIExpression(DW_OP_LLVM_fragment, 64, 32)
[...]
$reg2 = insn1
[...]
$reg3 = insn2

the history map would then contain the entries `[<DV1, insn1>, [<DV2, insn2>]`.
This would leave it up to the users of the map to be aware of
the relative order of the instructions, which e.g. could make
DwarfDebug::buildLocationList() needlessly complex. Instead, this patch
makes the history map structure monotonically increasing by dropping the
End pointer, and replacing that with explicit clobbering entries in the
vector. Each debug value has an "end index", which if set, points to the
entry in the vector that ends the debug value. The ending entry can
either be an overlapping debug value, or an instruction which clobbers
the register that the debug value is described by. The ending entry's
instruction can thus either be excluded or included in the debug value's
range. If the end index is not set, the debug value that the entry
introduces is valid until the end of the function.

Changes to test cases:

* DebugInfo/X86/pieces-3.ll: The range of the first DBG_VALUE, which
describes that the fragment (0, 64) is located in RDI, was
incorrectly ended by the clobbering of RAX, which the second
(non-overlapping) DBG_VALUE was described by. With this patch we
get a second entry that only describes RDI after that clobbering.

* DebugInfo/ARM/partial-subreg.ll: This test seems to indiciate a bug
in LiveDebugValues that is caused by it not being aware of fragments.
I have added some comments in the test case about that. Also, before
this patch DwarfDebug would incorrectly include a register-described
debug value from a preceding block in a location list entry.

Reviewers: aprantl, probinson, dblaikie, rnk, bjope

Reviewed By: aprantl

Subscribers: javed.absar, kristof.beyls, jdoerfert, llvm-commits

Tags: #debug-info, #llvm

Differential Revision: https://reviews.llvm.org/D59941

llvm-svn: 358072

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[DebugInfo] Rename DbgValueHistoryMap::{InstrRange -> Entry}, NFC

Summary:
In an upcoming commit the history map will be changed so that it
contains explicit entries for instructions that clobber pr

[DebugInfo] Rename DbgValueHistoryMap::{InstrRange -> Entry}, NFC

Summary:
In an upcoming commit the history map will be changed so that it
contains explicit entries for instructions that clobber preceding debug
values, rather than Begin- End range pairs, so generalize the name to
"Entry".

Also, prefix the iterator variable names in buildLocationList() with
"E". In an upcoming commit the entry will have query functions such as
"isD(e)b(u)gValue", which could at a glance make one confuse it for
iterations over MachineInstrs, so make the iterator names a bit more
distinct to avoid that.

Reviewers: aprantl

Reviewed By: aprantl

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59939

llvm-svn: 358060

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[DebugInfo] Make InstrRange into a class, NFC

Summary:
Replace use of std::pair by creating a class for the debug value
instruction ranges instead. This is a preparatory refactoring for
improving ha

[DebugInfo] Make InstrRange into a class, NFC

Summary:
Replace use of std::pair by creating a class for the debug value
instruction ranges instead. This is a preparatory refactoring for
improving handling of clobbered fragments.

In an upcoming commit the Begin pointer will become a PointerIntPair, so
it will be cleaner to have a getter for that.

Reviewers: aprantl

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59938

llvm-svn: 358059

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[DebugInfo] Stop changing labels for register-described parameter DBG_VALUEs

Summary:
This is a follow-up to D57510. This patch stops DebugHandlerBase from
changing the starting label for the first

[DebugInfo] Stop changing labels for register-described parameter DBG_VALUEs

Summary:
This is a follow-up to D57510. This patch stops DebugHandlerBase from
changing the starting label for the first non-overlapping,
register-described parameter DBG_VALUEs to the beginning of the
function. That code did not consider what defined the registers, which
could result in the ranges for the debug values starting before their
defining instructions. We currently do not emit debug values for
constant values directly at the start of the function, so this code is
still useful for such values, but my intention is to remove the code
from DebugHandlerBase completely when we get there. One reason for
removing it is that the code violates the history map's ranges, which I
think can make it quite confusing when troubleshooting.

In D57510, PrologEpilogInserter was amended so that parameter DBG_VALUEs
now are kept at the start of the entry block, even after emission of
prologue code. That was done to reduce the degradation of debug
completeness from this patch. PR40638 is another example, where the
lexical-scope trimming that LDV does, in combination with scheduling,
results in instructions after the prologue being left without locations.
There might be other cases where the DBG_VALUEs are pushed further down,
for which the DebugHandlerBase code may be helpful, but as it now quite
often result in incorrect locations, even after the prologue, it seems
better to remove that code, and try to work our way up with accurate
locations.

In the long run we should maybe not aim to provide accurate locations
inside the prologue. Some single location descriptions, at least those
referring to stack values, generate inaccurate values inside the
epilogue, so we maybe should not aim to achieve accuracy for location
lists. However, it seems that we now emit line number programs that can
result in GDB and LLDB stopping inside the prologue when doing line
number stepping into functions. See PR40188 for more information.

A summary of some of the changed test cases is available in PR40188#c2.

Reviewers: aprantl, dblaikie, rnk, jmorse

Reviewed By: aprantl

Subscribers: jdoerfert, jholewinski, jvesely, javed.absar, llvm-commits

Tags: #debug-info, #llvm

Differential Revision: https://reviews.llvm.org/D57511

llvm-svn: 353928

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Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the ne

Update the file headers across all of the LLVM projects in the monorepo
to reflect the new license.

We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.

Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.

llvm-svn: 351636

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[DebugInfo] Move several private headers to include directory

This patch moved the following files in lib/CodeGen/AsmPrinter/
AsmPrinterHandler.h
DbgEntityHistoryCalculator.h
DebugHandlerBase.

[DebugInfo] Move several private headers to include directory

This patch moved the following files in lib/CodeGen/AsmPrinter/
AsmPrinterHandler.h
DbgEntityHistoryCalculator.h
DebugHandlerBase.h
to include/llvm/CodeGen directory.

Such a change will enable Target to extend DebugHandlerBase
and emit Target specific debug info sections.

Signed-off-by: Yonghong Song <yhs@fb.com>

Differential Revision: https://reviews.llvm.org/D55755

llvm-svn: 349564

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Revert "[BTF] Add BTF DebugInfo"

This reverts commit 9c6b970db8bc63b28ce58a129bb1580a6a3c6caf.

llvm-svn: 348004

[BTF] Add BTF DebugInfo

This patch adds BPF Debug Format (BTF) as a standalone
LLVM debuginfo. The BTF related sections are directly
generated from IR. The BTF debuginfo is generated
only when the c

[BTF] Add BTF DebugInfo

This patch adds BPF Debug Format (BTF) as a standalone
LLVM debuginfo. The BTF related sections are directly
generated from IR. The BTF debuginfo is generated
only when the compilation target is BPF.

What is BTF?
============

First, the BPF is a linux kernel virtual machine
and widely used for tracing, networking and security.
https://www.kernel.org/doc/Documentation/networking/filter.txt
https://cilium.readthedocs.io/en/v1.2/bpf/

BTF is the debug info format for BPF, introduced in the below
linux patch
https://github.com/torvalds/linux/commit/69b693f0aefa0ed521e8bd02260523b5ae446ad7#diff-06fb1c8825f653d7e539058b72c83332
in the patch set mentioned in the below lwn article.
https://lwn.net/Articles/752047/

The BTF format is specified in the above github commit.
In summary, its layout looks like
struct btf_header
type subsection (a list of types)
string subsection (a list of strings)

With such information, the kernel and the user space is able to
pretty print a particular bpf map key/value. One possible example below:
Withtout BTF:
key: [ 0x01, 0x01, 0x00, 0x00 ]
With BTF:
key: struct t { a : 1; b : 1; c : 0}
where struct is defined as
struct t { char a; char b; short c; };

How BTF is generated?
=====================

Currently, the BTF is generated through pahole.
https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=68645f7facc2eb69d0aeb2dd7d2f0cac0feb4d69
and available in pahole v1.12
https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=4a21c5c8db0fcd2a279d067ecfb731596de822d4

Basically, the bpf program needs to be compiled with -g with
dwarf sections generated. The pahole is enhanced such that
a .BTF section can be generated based on dwarf. This format
of the .BTF section matches the format expected by
the kernel, so a bpf loader can just take the .BTF section
and load it into the kernel.
https://github.com/torvalds/linux/commit/8a138aed4a807ceb143882fb23a423d524dcdb35

The .BTF section layout is also specified in this patch:
with file include/llvm/BinaryFormat/BTF.h.

What use cases this patch tries to address?
===========================================

Currently, only the bpf instruction stream is required to
pass to the kernel. The kernel verifies it, jits it if configured
to do so, attaches it to a particular kernel attachment point,
and later executes when a particular event happens.

This patch tries to expand BTF to support two more use cases below:
(1). BPF supports subroutine calls.
During performance analysis, it would be good to
differentiate which call is hot instead of just
providing a virtual address. This would require to
pass a unique identifier for each subroutine to
the kernel, the subroutine name is a natual choice.
(2). If a particular jitted instruction is hot, we want
user to know which source line this jitted instruction
belongs to. This would require the source information
is available to various profiling tools.

Note that in a single ELF file,
. there may be multiple loadable bpf programs,
. for a particular to-be-loaded bpf instruction stream,
its instructions may come from multiple PROGBITS sections,
the bpf loader needs to merge them together to a single
consecutive insn stream before loading to the kernel.
For example:
section .text: subroutines funcFoo
section _progA: calling funcFoo
section _progB: calling funcFoo
The bpf loader could construct two loadable bpf instruction
streams and load them into the kernel:
. _progA funcFoo
. _progB funcFoo
So per ELF section function offset and instruction offset
will need to be adjusted before passing to the kernel, and
the kernel essentially expect only one code section regardless
of how many in the ELF file.

What do we propose and Why?
===========================

To support the above two use cases, we propose to
add an additional section, .BTF.ext, to the ELF file
which is the input of the bpf loader. A different section
is preferred since loader may need to manipulate it before
loading part of its data to the kernel.

The .BTF.ext section has a similar header to the .BTF section
and it contains two subsections for func_info and line_info.
. the func_info maps the func insn byte offset to a func
type in the .BTF type subsection.
. the line_info maps the insn byte offset to a line info.
. both func_info and line_info subsections are organized
by ELF PROGBITS AX sections.

pahole is not a good place to implement .BTF.ext as
pahole is mostly for structure hole information and more
importantly, we want to pass the actual code to the kernel.
. bpf program typically is small so storage overhead
should be small.
. in bpf land, it is totally possible that
an application loads the bpf program into the
kernel and then that application quits, so
holding debug info by the user space application
is not practical as you may not even know who
loads this bpf program.
. having source codes directly kept by kernel
would ease deployment since the original source
code does not need ship on every hosts and
kernel-devel package does not need to be
deployed even if kernel headers are used.

LLVM is a good place to implement.
. The only reliable time to get the source code is
during compilation time. This will result in both more
accurate information and easier deployment as
stated in the above.
. Another consideration is for JIT. The project like bcc
(https://github.com/iovisor/bcc)
use MCJIT to compile a C program into bpf insns and
load them to the kernel. The llvm generated BTF sections
will be readily available for such cases as well.

Design and implementation of emiting .BTF/.BTF.ext sections
===========================================================

The BTF debuginfo format is defined. Both .BTF and .BTF.ext
sections are generated directly from IR when both
"-target bpf" and "-g" are specified. Note that
dwarf sections are still generated as dwarf is used
by user space tools like llvm-objdump etc. for BPF target.

This patch also contains tests to verify generated
.BTF and .BTF.ext sections for all supported types, func_info
and line_info subsections. The patch is also tested
against linux kernel bpf sample tests and selftests.

Signed-off-by: Yonghong Song <yhs@fb.com>

Differential Revision: https://reviews.llvm.org/D53736

llvm-svn: 347999

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