Commit Graph

96 Commits

Author SHA1 Message Date
Hongtao Yu 705a4c149d [CSSPGO] Pseudo probe encoding and emission.
This change implements pseudo probe encoding and emission for CSSPGO. Please see RFC here for more context: https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s

Pseudo probes are in the form of intrinsic calls on IR/MIR but they do not turn into any machine instructions. Instead they are emitted into the binary as a piece of data in standalone sections.  The probe-specific sections are not needed to be loaded into memory at execution time, thus they do not incur a runtime overhead. 

**ELF object emission**

The binary data to emit are organized as two ELF sections, i.e, the `.pseudo_probe_desc` section and the `.pseudo_probe` section. The `.pseudo_probe_desc` section stores a function descriptor for each function and the `.pseudo_probe` section stores the actual probes, each fo which corresponds to an IR basic block or an IR function callsite. A function descriptor is stored as a module-level metadata during the compilation and is serialized into the object file during object emission.

Both the probe descriptors and pseudo probes can be emitted into a separate ELF section per function to leverage the linker for deduplication.  A `.pseudo_probe` section shares the same COMDAT group with the function code so that when the function is dead, the probes are dead and disposed too. On the contrary, a `.pseudo_probe_desc` section has its own COMDAT group. This is because even if a function is dead, its probes may be inlined into other functions and its descriptor is still needed by the profile generation tool.

The format of `.pseudo_probe_desc` section looks like:

```
.section   .pseudo_probe_desc,"",@progbits
.quad   6309742469962978389  // Func GUID
.quad   4294967295           // Func Hash
.byte   9                    // Length of func name
.ascii  "_Z5funcAi"          // Func name
.quad   7102633082150537521
.quad   138828622701
.byte   12
.ascii  "_Z8funcLeafi"
.quad   446061515086924981
.quad   4294967295
.byte   9
.ascii  "_Z5funcBi"
.quad   -2016976694713209516
.quad   72617220756
.byte   7
.ascii  "_Z3fibi"
```

For each `.pseudoprobe` section, the encoded binary data consists of a single function record corresponding to an outlined function (i.e, a function with a code entry in the `.text` section). A function record has the following format :

```
FUNCTION BODY (one for each outlined function present in the text section)
    GUID (uint64)
        GUID of the function
    NPROBES (ULEB128)
        Number of probes originating from this function.
    NUM_INLINED_FUNCTIONS (ULEB128)
        Number of callees inlined into this function, aka number of
        first-level inlinees
    PROBE RECORDS
        A list of NPROBES entries. Each entry contains:
          INDEX (ULEB128)
          TYPE (uint4)
            0 - block probe, 1 - indirect call, 2 - direct call
          ATTRIBUTE (uint3)
            reserved
          ADDRESS_TYPE (uint1)
            0 - code address, 1 - address delta
          CODE_ADDRESS (uint64 or ULEB128)
            code address or address delta, depending on ADDRESS_TYPE
    INLINED FUNCTION RECORDS
        A list of NUM_INLINED_FUNCTIONS entries describing each of the inlined
        callees.  Each record contains:
          INLINE SITE
            GUID of the inlinee (uint64)
            ID of the callsite probe (ULEB128)
          FUNCTION BODY
            A FUNCTION BODY entry describing the inlined function.
```

To support building a context-sensitive profile, probes from inlinees are grouped by their inline contexts. An inline context is logically a call path through which a callee function lands in a caller function. The probe emitter builds an inline tree based on the debug metadata for each outlined function in the form of a trie tree. A tree root is the outlined function. Each tree edge stands for a callsite where inlining happens. Pseudo probes originating from an inlinee function are stored in a tree node and the tree path starting from the root all the way down to the tree node is the inline context of the probes. The emission happens on the whole tree top-down recursively. Probes of a tree node will be emitted altogether with their direct parent edge. Since a pseudo probe corresponds to a real code address, for size savings, the address is encoded as a delta from the previous probe except for the first probe. Variant-sized integer encoding, aka LEB128, is used for address delta and probe index.

**Assembling**

Pseudo probes can be printed as assembly directives alternatively. This allows for good assembly code readability and also provides a view of how optimizations and pseudo probes affect each other, especially helpful for diff time assembly analysis.

A pseudo probe directive has the following operands in order: function GUID, probe index, probe type, probe attributes and inline context. The directive is generated by the compiler and can be parsed by the assembler to form an encoded `.pseudoprobe` section in the object file.

A example assembly looks like:

```
foo2: # @foo2
# %bb.0: # %bb0
pushq %rax
testl %edi, %edi
.pseudoprobe 837061429793323041 1 0 0
je .LBB1_1
# %bb.2: # %bb2
.pseudoprobe 837061429793323041 6 2 0
callq foo
.pseudoprobe 837061429793323041 3 0 0
.pseudoprobe 837061429793323041 4 0 0
popq %rax
retq
.LBB1_1: # %bb1
.pseudoprobe 837061429793323041 5 1 0
callq *%rsi
.pseudoprobe 837061429793323041 2 0 0
.pseudoprobe 837061429793323041 4 0 0
popq %rax
retq
# -- End function
.section .pseudo_probe_desc,"",@progbits
.quad 6699318081062747564
.quad 72617220756
.byte 3
.ascii "foo"
.quad 837061429793323041
.quad 281547593931412
.byte 4
.ascii "foo2"
```

With inlining turned on, the assembly may look different around %bb2 with an inlined probe:

```
# %bb.2:                                # %bb2
.pseudoprobe    837061429793323041 3 0
.pseudoprobe    6699318081062747564 1 0 @ 837061429793323041:6
.pseudoprobe    837061429793323041 4 0
popq    %rax
retq
```

**Disassembling**

We have a disassembling tool (llvm-profgen) that can display disassembly alongside with pseudo probes. So far it only supports ELF executable file.

An example disassembly looks like:

```
00000000002011a0 <foo2>:
  2011a0: 50                    push   rax
  2011a1: 85 ff                 test   edi,edi
  [Probe]:  FUNC: foo2  Index: 1  Type: Block
  2011a3: 74 02                 je     2011a7 <foo2+0x7>
  [Probe]:  FUNC: foo2  Index: 3  Type: Block
  [Probe]:  FUNC: foo2  Index: 4  Type: Block
  [Probe]:  FUNC: foo   Index: 1  Type: Block  Inlined: @ foo2:6
  2011a5: 58                    pop    rax
  2011a6: c3                    ret
  [Probe]:  FUNC: foo2  Index: 2  Type: Block
  2011a7: bf 01 00 00 00        mov    edi,0x1
  [Probe]:  FUNC: foo2  Index: 5  Type: IndirectCall
  2011ac: ff d6                 call   rsi
  [Probe]:  FUNC: foo2  Index: 4  Type: Block
  2011ae: 58                    pop    rax
  2011af: c3                    ret
```

Reviewed By: wmi

Differential Revision: https://reviews.llvm.org/D91878
2020-12-10 17:29:28 -08:00
Mitch Phillips 7ead5f5aa3 Revert "[CSSPGO] Pseudo probe encoding and emission."
This reverts commit b035513c06.

Reason: Broke the ASan buildbots:
  http://lab.llvm.org:8011/#/builders/5/builds/2269
2020-12-10 15:53:39 -08:00
Hongtao Yu b035513c06 [CSSPGO] Pseudo probe encoding and emission.
This change implements pseudo probe encoding and emission for CSSPGO. Please see RFC here for more context: https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s

Pseudo probes are in the form of intrinsic calls on IR/MIR but they do not turn into any machine instructions. Instead they are emitted into the binary as a piece of data in standalone sections.  The probe-specific sections are not needed to be loaded into memory at execution time, thus they do not incur a runtime overhead. 

**ELF object emission**

The binary data to emit are organized as two ELF sections, i.e, the `.pseudo_probe_desc` section and the `.pseudo_probe` section. The `.pseudo_probe_desc` section stores a function descriptor for each function and the `.pseudo_probe` section stores the actual probes, each fo which corresponds to an IR basic block or an IR function callsite. A function descriptor is stored as a module-level metadata during the compilation and is serialized into the object file during object emission.

Both the probe descriptors and pseudo probes can be emitted into a separate ELF section per function to leverage the linker for deduplication.  A `.pseudo_probe` section shares the same COMDAT group with the function code so that when the function is dead, the probes are dead and disposed too. On the contrary, a `.pseudo_probe_desc` section has its own COMDAT group. This is because even if a function is dead, its probes may be inlined into other functions and its descriptor is still needed by the profile generation tool.

The format of `.pseudo_probe_desc` section looks like:

```
.section   .pseudo_probe_desc,"",@progbits
.quad   6309742469962978389  // Func GUID
.quad   4294967295           // Func Hash
.byte   9                    // Length of func name
.ascii  "_Z5funcAi"          // Func name
.quad   7102633082150537521
.quad   138828622701
.byte   12
.ascii  "_Z8funcLeafi"
.quad   446061515086924981
.quad   4294967295
.byte   9
.ascii  "_Z5funcBi"
.quad   -2016976694713209516
.quad   72617220756
.byte   7
.ascii  "_Z3fibi"
```

For each `.pseudoprobe` section, the encoded binary data consists of a single function record corresponding to an outlined function (i.e, a function with a code entry in the `.text` section). A function record has the following format :

```
FUNCTION BODY (one for each outlined function present in the text section)
    GUID (uint64)
        GUID of the function
    NPROBES (ULEB128)
        Number of probes originating from this function.
    NUM_INLINED_FUNCTIONS (ULEB128)
        Number of callees inlined into this function, aka number of
        first-level inlinees
    PROBE RECORDS
        A list of NPROBES entries. Each entry contains:
          INDEX (ULEB128)
          TYPE (uint4)
            0 - block probe, 1 - indirect call, 2 - direct call
          ATTRIBUTE (uint3)
            reserved
          ADDRESS_TYPE (uint1)
            0 - code address, 1 - address delta
          CODE_ADDRESS (uint64 or ULEB128)
            code address or address delta, depending on ADDRESS_TYPE
    INLINED FUNCTION RECORDS
        A list of NUM_INLINED_FUNCTIONS entries describing each of the inlined
        callees.  Each record contains:
          INLINE SITE
            GUID of the inlinee (uint64)
            ID of the callsite probe (ULEB128)
          FUNCTION BODY
            A FUNCTION BODY entry describing the inlined function.
```

To support building a context-sensitive profile, probes from inlinees are grouped by their inline contexts. An inline context is logically a call path through which a callee function lands in a caller function. The probe emitter builds an inline tree based on the debug metadata for each outlined function in the form of a trie tree. A tree root is the outlined function. Each tree edge stands for a callsite where inlining happens. Pseudo probes originating from an inlinee function are stored in a tree node and the tree path starting from the root all the way down to the tree node is the inline context of the probes. The emission happens on the whole tree top-down recursively. Probes of a tree node will be emitted altogether with their direct parent edge. Since a pseudo probe corresponds to a real code address, for size savings, the address is encoded as a delta from the previous probe except for the first probe. Variant-sized integer encoding, aka LEB128, is used for address delta and probe index.

**Assembling**

Pseudo probes can be printed as assembly directives alternatively. This allows for good assembly code readability and also provides a view of how optimizations and pseudo probes affect each other, especially helpful for diff time assembly analysis.

A pseudo probe directive has the following operands in order: function GUID, probe index, probe type, probe attributes and inline context. The directive is generated by the compiler and can be parsed by the assembler to form an encoded `.pseudoprobe` section in the object file.

A example assembly looks like:

```
foo2: # @foo2
# %bb.0: # %bb0
pushq %rax
testl %edi, %edi
.pseudoprobe 837061429793323041 1 0 0
je .LBB1_1
# %bb.2: # %bb2
.pseudoprobe 837061429793323041 6 2 0
callq foo
.pseudoprobe 837061429793323041 3 0 0
.pseudoprobe 837061429793323041 4 0 0
popq %rax
retq
.LBB1_1: # %bb1
.pseudoprobe 837061429793323041 5 1 0
callq *%rsi
.pseudoprobe 837061429793323041 2 0 0
.pseudoprobe 837061429793323041 4 0 0
popq %rax
retq
# -- End function
.section .pseudo_probe_desc,"",@progbits
.quad 6699318081062747564
.quad 72617220756
.byte 3
.ascii "foo"
.quad 837061429793323041
.quad 281547593931412
.byte 4
.ascii "foo2"
```

With inlining turned on, the assembly may look different around %bb2 with an inlined probe:

```
# %bb.2:                                # %bb2
.pseudoprobe    837061429793323041 3 0
.pseudoprobe    6699318081062747564 1 0 @ 837061429793323041:6
.pseudoprobe    837061429793323041 4 0
popq    %rax
retq
```

**Disassembling**

We have a disassembling tool (llvm-profgen) that can display disassembly alongside with pseudo probes. So far it only supports ELF executable file.

An example disassembly looks like:

```
00000000002011a0 <foo2>:
  2011a0: 50                    push   rax
  2011a1: 85 ff                 test   edi,edi
  [Probe]:  FUNC: foo2  Index: 1  Type: Block
  2011a3: 74 02                 je     2011a7 <foo2+0x7>
  [Probe]:  FUNC: foo2  Index: 3  Type: Block
  [Probe]:  FUNC: foo2  Index: 4  Type: Block
  [Probe]:  FUNC: foo   Index: 1  Type: Block  Inlined: @ foo2:6
  2011a5: 58                    pop    rax
  2011a6: c3                    ret
  [Probe]:  FUNC: foo2  Index: 2  Type: Block
  2011a7: bf 01 00 00 00        mov    edi,0x1
  [Probe]:  FUNC: foo2  Index: 5  Type: IndirectCall
  2011ac: ff d6                 call   rsi
  [Probe]:  FUNC: foo2  Index: 4  Type: Block
  2011ae: 58                    pop    rax
  2011af: c3                    ret
```

Reviewed By: wmi

Differential Revision: https://reviews.llvm.org/D91878
2020-12-10 09:50:08 -08:00
serge-sans-paille 9218ff50f9 llvmbuildectomy - replace llvm-build by plain cmake
No longer rely on an external tool to build the llvm component layout.

Instead, leverage the existing `add_llvm_componentlibrary` cmake function and
introduce `add_llvm_component_group` to accurately describe component behavior.

These function store extra properties in the created targets. These properties
are processed once all components are defined to resolve library dependencies
and produce the header expected by llvm-config.

Differential Revision: https://reviews.llvm.org/D90848
2020-11-13 10:35:24 +01:00
jasonliu d65557d15d [NFC][XCOFF][AIX] Refactor get/setContainingCsect
Summary:
For current architect, we always require setContainingCsect to be
called on every MCSymbol got used in XCOFF context.
This is very hard to achieve because symbols gets created everywhere
 and other MCSymbol types(ELF, COFF) do not have similar rules.
It's very easy to miss setting the containing csect, and we would
need to add a lot of XCOFF specialized code around some common code area.

This patch intendeds to do
1. Rely on getFragment().getParent() to get csect from labels.
2. Only use get/setRepresentedCsect (was get/setContainingCsect)
if symbol itself represents a csect.

Reviewers: DiggerLin, hubert.reinterpretcast, daltenty

Differential Revision: https://reviews.llvm.org/D77080
2020-04-03 13:33:12 +00:00
Benjamin Kramer 854f268ca6 [MC] Move deprecation infos from MCTargetDesc to MCInstrInfo
This allows emitting it only when the feature is used by a target.
Shrinks Release+Asserts clang by 900k.
2020-03-29 21:20:40 +02:00
serge-sans-paille ac1d23ed7d Replace MCTargetOptionsCommandFlags.inc and CommandFlags.inc by runtime registration
MCTargetOptionsCommandFlags.inc and CommandFlags.inc are headers which contain
cl::opt with static storage.
These headers are meant to be incuded by tools to make it easier to parametrize
codegen/mc.

However, these headers are also included in at least two libraries: lldCommon
and handle-llvm. As a result, when creating DYLIB, clang-cpp holds a reference
to the options, and lldCommon holds another reference. Linking the two in a
single executable, as zig does[0], results in a double registration.

This patch explores an other approach: the .inc files are moved to regular
files, and the registration happens on-demand through static declaration of
options in the constructor of a static object.

[0] https://bugzilla.redhat.com/show_bug.cgi?id=1756977#c5

Differential Revision: https://reviews.llvm.org/D75579
2020-03-17 14:01:30 +01:00
Fangrui Song 9574757dba [MC] Delete MCCodePadder
D34393 added MCCodePadder as an infrastructure for padding code with
NOP instructions. It lacked tests and was not being worked on since
then.

Intel has now worked on an assembler patch to mitigate performance loss
after applying microcode update for the Jump Conditional Code Erratum.

https://www.intel.com/content/www/us/en/support/articles/000055650/processors.html

This new patch shares similarity with MCCodePadder, but has a concrete
use case in mind and is being actively developed. The infrastructure it
introduces can potentially be used for general performance improvement
via alignment. Delete the unused MCCodePadder so that people can develop
the new feature from a clean state.

Reviewed By: jyknight, skan

Differential Revision: https://reviews.llvm.org/D71106
2019-12-09 19:21:31 -08:00
Tom Stellard ab411801b8 [cmake] Explicitly mark libraries defined in lib/ as "Component Libraries"
Summary:
Most libraries are defined in the lib/ directory but there are also a
few libraries defined in tools/ e.g. libLLVM, libLTO.  I'm defining
"Component Libraries" as libraries defined in lib/ that may be included in
libLLVM.so.  Explicitly marking the libraries in lib/ as component
libraries allows us to remove some fragile checks that attempt to
differentiate between lib/ libraries and tools/ libraires:

1. In tools/llvm-shlib, because
llvm_map_components_to_libnames(LIB_NAMES "all") returned a list of
all libraries defined in the whole project, there was custom code
needed to filter out libraries defined in tools/, none of which should
be included in libLLVM.so.  This code assumed that any library
defined as static was from lib/ and everything else should be
excluded.

With this change, llvm_map_components_to_libnames(LIB_NAMES, "all")
only returns libraries that have been added to the LLVM_COMPONENT_LIBS
global cmake property, so this custom filtering logic can be removed.
Doing this also fixes the build with BUILD_SHARED_LIBS=ON
and LLVM_BUILD_LLVM_DYLIB=ON.

2. There was some code in llvm_add_library that assumed that
libraries defined in lib/ would not have LLVM_LINK_COMPONENTS or
ARG_LINK_COMPONENTS set.  This is only true because libraries
defined lib lib/ use LLVMBuild.txt and don't set these values.
This code has been fixed now to check if the library has been
explicitly marked as a component library, which should now make it
easier to remove LLVMBuild at some point in the future.

I have tested this patch on Windows, MacOS and Linux with release builds
and the following combinations of CMake options:

- "" (No options)
- -DLLVM_BUILD_LLVM_DYLIB=ON
- -DLLVM_LINK_LLVM_DYLIB=ON
- -DBUILD_SHARED_LIBS=ON
- -DBUILD_SHARED_LIBS=ON -DLLVM_BUILD_LLVM_DYLIB=ON
- -DBUILD_SHARED_LIBS=ON -DLLVM_LINK_LLVM_DYLIB=ON

Reviewers: beanz, smeenai, compnerd, phosek

Reviewed By: beanz

Subscribers: wuzish, jholewinski, arsenm, dschuff, jyknight, dylanmckay, sdardis, nemanjai, jvesely, nhaehnle, mgorny, mehdi_amini, sbc100, jgravelle-google, hiraditya, aheejin, fedor.sergeev, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, steven_wu, rogfer01, MartinMosbeck, brucehoult, the_o, dexonsmith, PkmX, jocewei, jsji, dang, Jim, lenary, s.egerton, pzheng, sameer.abuasal, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70179
2019-11-21 10:48:08 -08:00
Sean Fertile f09d54ed2a Boilerplate for producing XCOFF object files from the PowerPC backend.
Stubs out a number of the classes needed to produce a new object file format
(XCOFF) for the powerpc-aix target. For testing input is an empty module which
produces an object file with just a file header.

Differential Revision: https://reviews.llvm.org/D61694

llvm-svn: 365541
2019-07-09 19:21:01 +00:00
Eli Friedman a6e3a823b3 Revert BTF commit series.
The initial patch was not reviewed, and does not have any tests;
it should not have been merged.

This reverts 344395, 344390, 344387, 344385, 344381, 344376,
and 344366.

llvm-svn: 344405
2018-10-12 19:41:05 +00:00
Yonghong Song 6c2327a09e [BPF] Add BTF generation for BPF target
BTF is the debug format for BPF, a kernel virtual machine
and widely used for tracing, networking and security, etc ([1]).

Currently only instruction streams are passed to kernel,
the kernel verifier verifies them before execution. In order to
provide better visibility of bpf programs to user space
tools, some debug information, e.g., function names and
debug line information are desirable for kernel so tools
can get such information with better annotation
for jited instructions for performance or other reasons.

The dwarf is too complicated in kernel and for BPF.
Hence, BTF is designed to be the debug format for BPF ([2]).
Right now, pahole supports BTF for types, which
are generated based on dwarf sections in the ELF file.

In order to annotate performance metrics for jited bpf insns,
it is necessary to pass debug line info to the kernel.
Furthermore, we want to pass the actual code to the
kernel because of the following reasons:

. 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.
. 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.

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
use MCJIT to compile a C program into bpf insns and
load them to the kernel ([3]). The generated BTF sections
will be readily available for such cases as well.

This patch implemented generation of BTF info in llvm
compiler. The BTF related sections will be generated
when both -target bpf and -g are specified. Two sections
are generated:
  .BTF contains all the type and string information, and
  .BTF.ext contains the func_info and line_info.

The separation is related to how two sections are used
differently in bpf loader, e.g., linux libbpf ([4]).
The .BTF section can be loaded into the kernel directly
while .BTF.ext needs loader manipulation before loading
to the kernel. The format of the each section is roughly
defined in llvm:include/llvm/MC/MCBTFContext.h and
from the implementation in llvm:lib/MC/MCBTFContext.cpp.
A later example also shows the contents in each section.

The type and func_info are gathered during CodeGen/AsmPrinter
by traversing dwarf debug_info. The line_info is
gathered in MCObjectStreamer before writing to
the object file. After all the information is gathered,
the two sections are emitted in MCObjectStreamer::finishImpl.

With cmake CMAKE_BUILD_TYPE=Debug, the compiler can
dump out all the tables except insn offset, which
will be resolved later as relocation records.
The debug type "btf" is used for BTFContext dump.

Dwarf tests the debug info generation with
llvm-dwarfdump to decode the binary sections and
check whether the result is expected. Currently
we do not have such a tool yet. We will implement
btf dump functionality in bpftool ([5]) as the bpftool is
considered the recommended tool for bpf introspection.
The implementation for type and func_info is tested
with linux kernel test cases. The line_info is visually
checked with dump from linux kernel libbpf ([4]) and
checked with readelf dumping section raw data.

Note that the .BTF and .BTF.ext information will not
be emitted to assembly code and there is no assembler
support for BTF either.

In the below, with a clang/llvm built with CMAKE_BUILD_TYPE=Debug,
Each table contents are shown for a simple C program.

  -bash-4.2$ cat -n test.c
     1  struct A {
     2    int a;
     3    char b;
     4  };
     5
     6  int test(struct A *t) {
     7    return t->a;
     8  }
  -bash-4.2$ clang -O2 -target bpf -g -mllvm -debug-only=btf -c test.c
  Type Table:
  [1] FUNC name_off=1 info=0x0c000001 size/type=2
        param_type=3
  [2] INT name_off=12 info=0x01000000 size/type=4
        desc=0x01000020
  [3] PTR name_off=0 info=0x02000000 size/type=4
  [4] STRUCT name_off=16 info=0x04000002 size/type=8
        name_off=18 type=2 bit_offset=0
        name_off=20 type=5 bit_offset=32
  [5] INT name_off=22 info=0x01000000 size/type=1
        desc=0x02000008

  String Table:
  0 :
  1 : test
  6 : .text
  12 : int
  16 : A
  18 : a
  20 : b
  22 : char
  27 : test.c
  34 : int test(struct A *t) {
  58 :   return t->a;

  FuncInfo Table:
  sec_name_off=6
        insn_offset=<Omitted> type_id=1

  LineInfo Table:
  sec_name_off=6
        insn_offset=<Omitted> file_name_off=27 line_off=34 line_num=6 column_num=0
        insn_offset=<Omitted> file_name_off=27 line_off=58 line_num=7 column_num=3
  -bash-4.2$ readelf -S test.o
  ......
    [12] .BTF              PROGBITS         0000000000000000  0000028d
       00000000000000c1  0000000000000000           0     0     1
    [13] .BTF.ext          PROGBITS         0000000000000000  0000034e
       0000000000000050  0000000000000000           0     0     1
    [14] .rel.BTF.ext      REL              0000000000000000  00000648
       0000000000000030  0000000000000010          16    13     8
  ......
  -bash-4.2$

The latest linux kernel ([6]) can already support .BTF with type information.
The [7] has the reference implementation in linux kernel side
to support .BTF.ext func_info. The .BTF.ext line_info support is not
implemented yet. If you have difficulty accessing [6], you can
manually do the following to access the code:

  git clone https://github.com/yonghong-song/bpf-next-linux.git
  cd bpf-next-linux
  git checkout btf

The change will push to linux kernel soon once this patch is landed.

References:
[1]. https://www.kernel.org/doc/Documentation/networking/filter.txt
[2]. https://lwn.net/Articles/750695/
[3]. https://github.com/iovisor/bcc
[4]. https://github.com/torvalds/linux/tree/master/tools/lib/bpf
[5]. https://github.com/torvalds/linux/tree/master/tools/bpf/bpftool
[6]. https://github.com/torvalds/linux
[7]. https://github.com/yonghong-song/bpf-next-linux/tree/btf

Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>

Differential Revision: https://reviews.llvm.org/D52950

llvm-svn: 344366
2018-10-12 17:01:46 +00:00
Oliver Stannard a930111c70 [Asm] Add debug printing for assembler macros
This adds some debug printing (gated behind the "asm-macros" debug flag) which
can help tracing complicated assembly macros.

Differential revision: https://reviews.llvm.org/D43937

llvm-svn: 326795
2018-03-06 14:07:01 +00:00
Omer Paparo Bivas 2251c79aba [MC] Adding code padding for performance stability - infrastructure. NFC.
Infrastructure designed for padding code with nop instructions in key places such that preformance improvement will be achieved.
The infrastructure is implemented such that the padding is done in the Assembler after the layout is done and all IPs and alignments are known.
This patch by itself in a NFC. Future patches will make use of this infrastructure to implement required policies for code padding.

Reviewers:
aaboud
zvi
craig.topper
gadi.haber

Differential revision: https://reviews.llvm.org/D34393

Change-Id: I92110d0c0a757080a8405636914a93ef6f8ad00e
llvm-svn: 316413
2017-10-24 06:16:03 +00:00
Sam Clegg 9fa8af6f82 Rename WinCOFFStreamer.cpp -> MCWinCOFFStreamer.cpp
For consistency with other MC*Streamer.cpp files and
the header file.

Differential Revision: https://reviews.llvm.org/D34466

llvm-svn: 305952
2017-06-21 20:58:17 +00:00
Dan Gohman 18eafb6c68 [WebAssembly] Add skeleton MC support for the Wasm container format
This just adds the basic skeleton for supporting a new object file format.
All of the actual encoding will be implemented in followup patches.

Differential Revision: https://reviews.llvm.org/D26722

llvm-svn: 295803
2017-02-22 01:23:18 +00:00
Peter Collingbourne 0da86301ad Revert r283690, "MC: Remove unused entities."
llvm-svn: 283814
2016-10-10 22:49:37 +00:00
Peter Collingbourne cc723cccab MC: Remove unused entities.
llvm-svn: 283691
2016-10-09 04:39:13 +00:00
Rafael Espindola d86e8bb0ed Delete MCCodeGenInfo.
MC doesn't really care about CodeGen stuff, so this was just
complicating target initialization.

llvm-svn: 274258
2016-06-30 18:25:11 +00:00
Rafael Espindola ebd9193b57 Move ObjectYAML code to a new library.
It is only ever used by obj2yaml and yaml2obj. No point in linking it
everywhere.

llvm-svn: 262368
2016-03-01 19:15:06 +00:00
Reid Kleckner 2214ed8937 Reland "[CodeView] Use assembler directives for line tables"
This reverts commit r259126 and relands r259117.

This time with updated library dependencies.

llvm-svn: 259130
2016-01-29 00:49:42 +00:00
Reid Kleckner 00d9639c24 Revert "[CodeView] Use assembler directives for line tables"
This reverts commit r259117.

The LineInfo constructor is defined in the codeview library and we have
to link against it now. Doing that isn't trivial, so reverting for now.

llvm-svn: 259126
2016-01-29 00:13:28 +00:00
Reid Kleckner c62e379d22 [CodeView] Use assembler directives for line tables
Adds a new family of .cv_* directives to LLVM's variant of GAS syntax:

- .cv_file: Similar to DWARF .file directives

- .cv_loc: Similar to the DWARF .loc directive, but starts with a
  function id. CodeView line tables are emitted by function instead of
  by compilation unit, so we needed an extra field to communicate this.
  Rather than overloading the .loc direction further, we decided it was
  better to have our own directive.

- .cv_stringtable: Emits the codeview string table at the current
  position. Currently this just contains the filenames as
  null-terminated strings.

- .cv_filechecksums: Emits the file checksum table for all files used
  with .cv_file so far. There is currently no support for emitting
  actual checksums, just filenames.

This moves the line table emission code down into the assembler.  This
is in preparation for implementing the inlined call site line table
format. The inline line table format encoding algorithm requires knowing
the absolute code offsets, so it must run after the assembler has laid
out the code.

David Majnemer collaborated on this patch.

llvm-svn: 259117
2016-01-28 23:31:52 +00:00
Benjamin Kramer f57c1977c1 Reflect the MC/MCDisassembler split on the include/ level.
No functional change, just moving code around.

llvm-svn: 258818
2016-01-26 16:44:37 +00:00
Chandler Carruth 8d736236d3 [ptr-traits] Split the MCFragment type hierarchy out of the MCAssembler
header to its own header, allowing users of fragments to have a narrower
header file, and avoid circular header dependencies when getting the
definition of MCSection prior to inspecting traits on MCSection
pointers.

This is part of a series of patches to allow LLVM to check for complete
pointee types when computing its pointer traits. This is absolutely
necessary to get correct (or reproducible) results for things like how
many low bits are guaranteed to be zero.

Note that this doesn't in any way change the design of MC, it is just
moving code around to allow the *header files* to be more fine grained.
Without this, it is impossible to get a complete type for MCSection
where it is needed.

If anyone would prefer a different slicing of the header files, I'm
happy to oblige of course. =]

llvm-svn: 256548
2015-12-29 09:06:16 +00:00
Duncan P. N. Exon Smith f862f87ff2 MC: Remove the copy of MCSchedModel in MCSubtargetInfo
`MCSchedModel` is large.  Make `MCSchedModel::GetDefaultSchedModel()`
return by-reference instead of by-value, so we can store a pointer in
`MCSubtargetInfo::CPUSchedModel` instead of a copy.

Note: since `MCSchedModel` is POD, this doesn't create a static
constructor.

llvm-svn: 241947
2015-07-10 22:13:43 +00:00
Rafael Espindola 95fb9b93ed Merge MCELF.h into MCSymbolELF.h.
Now that we have a dedicated type for ELF symbol, these helper functions can
become member function of MCSymbolELF.

llvm-svn: 238864
2015-06-02 20:38:46 +00:00
Pete Cooper 80735a2d8e Move some methods to a new MCInstrDesc.cpp file to allow includes to be trimmed. NFC.
MCInstrDesc.h includes things like MCInst.h which i can now remove after this.  That will be a future commit.

Reviewed by Jim Grosbach.

llvm-svn: 237478
2015-05-15 21:29:43 +00:00
Zachary Turner 3bd47cee78 Use ADDITIONAL_HEADER_DIRS in all LLVM CMake projects.
This allows IDEs to recognize the entire set of header files for
each of the core LLVM projects.

Differential Revision: http://reviews.llvm.org/D7526
Reviewed By: Chris Bieneman

llvm-svn: 228798
2015-02-11 03:28:02 +00:00
Sean Silva 888320e9fa Nuke MCAnalysis.
The code is buggy and barely tested. It is also mostly boilerplate.
(This includes MCObjectDisassembler, which is the interface to that
functionality)

Following an IRC discussion with Jim Grosbach, it seems sensible to just
nuke the whole lot of functionality, and dig it up from VCS if
necessary (I hope not!).

All of this stuff appears to have been added in a huge patch dump (look
at the timeframe surrounding e.g. r182628) where almost every patch
seemed to be untested and not reviewed before being committed.
Post-review responses to the patches were never addressed. I don't think
any of it would have passed pre-commit review.

I doubt anyone is depending on this, since this code appears to be
extremely buggy. In limited testing that Michael Spencer and I did, we
couldn't find a single real-world object file that wouldn't crash the
CFG reconstruction stuff. The symbolizer stuff has O(n^2) behavior and
so is not much use to anyone anyway. It seemed simpler to remove them as
a whole. Most of this code is boilerplate, which is the only way it was
able to scrape by 60% coverage.

HEADSUP: Modules folks, some files I nuked were referenced from
include/llvm/module.modulemap; I just deleted the references. Hopefully
that is the right fix (one was a FIXME though!).

llvm-svn: 216983
2014-09-02 22:32:20 +00:00
Saleem Abdulrasool 64a8cc7d0d MC: split Win64EHUnwindEmitter into a shared streamer
This changes Win64EHEmitter into a utility WinEH UnwindEmitter that can be
shared across multiple architectures and a target specific bit which is
overridden (Win64::UnwindEmitter).  This enables sharing the section selection
code across X86 and the intended use in ARM for emitting unwind information for
Windows on ARM.

llvm-svn: 215050
2014-08-07 02:59:41 +00:00
Rafael Espindola 5addace56d Finish inverting the MC -> Object dependency.
There were still some disassembler bits in lib/MC, but their use of Object
was only visible in the includes they used, not in the symbols.

llvm-svn: 213808
2014-07-23 22:26:07 +00:00
Rafael Espindola 97de474a36 Invert the MC -> Object dependency.
Now that we have a lib/MC/MCAnalysis, the dependency was there just because
of two helper classes. Move the two over to MC.

This will allow IRObjectFile to parse inline assembly.

llvm-svn: 212248
2014-07-03 02:01:39 +00:00
Rafael Espindola cbc5ac7a7e Move CFG building code to a new lib/MC/MCAnalysis library.
The new library is 150KB on a Release+Asserts build, so it is quiet a bit of
code that regular users of MC don't need to link with now.

llvm-svn: 212209
2014-07-02 19:49:34 +00:00
Weiming Zhao 8c89973462 [ARM] [MC] Refactor the constant pool classes
ARMTargetStreamer implements ConstantPool and AssmeblerConstantPools
to keep track of assembler-generated constant pools that are used for
ldr-pseudo.

When implementing ldr-pseudo for AArch64, these two classes can be reused.
So this patch factors them out from ARM target to the general MC lib.

llvm-svn: 211198
2014-06-18 18:17:25 +00:00
Rafael Espindola 3d082fa507 Fix pr19645.
The fix itself is fairly simple: move getAccessVariant to MCValue so that we
replace the old weak expression evaluation with the far more general
EvaluateAsRelocatable.

This then requires that EvaluateAsRelocatable stop when it finds a non
trivial reference kind. And that in turn requires the ELF writer to look
harder for weak references.

Last but not least, this found a case where we were being bug by bug
compatible with gas and accepting an invalid input. I reported pr19647
to track it.

llvm-svn: 207920
2014-05-03 19:57:04 +00:00
Evgeniy Stepanov 0a951b775e Create MCTargetOptions.
For now it contains a single flag, SanitizeAddress, which enables
AddressSanitizer instrumentation of inline assembly.

Patch by Yuri Gorshenin.

llvm-svn: 206971
2014-04-23 11:16:03 +00:00
Tim Northover 53d3251851 MachO: Add linker-optimisation hint framework to MC.
Another part of the ARM64 backend (so tests will be following soon).
This is currently used by the linker to relax adrp/ldr pairs into nops
where possible, though could well be more broadly applicable.

llvm-svn: 205084
2014-03-29 07:34:53 +00:00
Rafael Espindola 7fadc0ea7d Look through variables when computing relocations.
Given

bar = foo + 4
	.long bar

MC would eat the 4. GNU as includes it in the relocation. The rule seems to be
that a variable that defines a symbol is used in the relocation and one that
does not define a symbol is evaluated and the result included in the relocation.

Fixing this unfortunately required some other changes:

* Since the variable is now evaluated, it would prevent the ELF writer from
  noticing the weakref marker the elf streamer uses. This patch then replaces
  that with a VariantKind in MCSymbolRefExpr.

* Using VariantKind then requires us to look past other VariantKind to see

	.weakref	bar,foo
	call	bar@PLT

  doing this also fixes

	zed = foo +2
	call zed@PLT

  so that is a good thing.

* Looking past VariantKind means that the relocation selection has to use
  the fixup instead of the target.

This is a reboot of the previous fixes for MC. I will watch the sanitizer
buildbot and wait for a build before adding back the previous fixes.

llvm-svn: 204294
2014-03-20 02:12:01 +00:00
Rafael Espindola 8837995b52 Remove MCPureStreamer.
We moved MCJIT to use native object formats a long time ago and R600
now uses ELF, so it was dead.

llvm-svn: 202408
2014-02-27 16:17:34 +00:00
Rafael Espindola 43c4e24fad Add a MCAsmInfoELF class and factor some code into it.
We had a MCAsmInfoCOFF, but no common class for all the ELF MCAsmInfos before.

llvm-svn: 192760
2013-10-16 01:34:32 +00:00
Ahmed Bougacha 1792647942 MC CFG: Add YAML MCModule representation to enable MC CFG testing.
Like yaml ObjectFiles, this will be very useful for testing the MC CFG
implementation (mostly MCObjectDisassembler), by matching the output
with YAML, and for potential users of the MC CFG, by using it as an input.

There isn't much to the actual format, it is just a serialization of the
MCModule class. Of note:
  - Basic block references (pred/succ, ..) are represented by the BB's
    start address.
  - Just as in the MC CFG, instructions are MCInsts with a size.
  - Operands have a prefix representing the type (only register and
    immediate supported here).
  - Instruction opcodes are represented by their names; enum values aren't
    stable, enum names mostly are: usually, a change to a name would need
    lots of changes in the backend anyway.
    Same with registers.

All in all, an example is better than 1000 words, here goes:

A simple binary:

  Disassembly of section __TEXT,__text:
  _main:
  100000f9c:      48 8b 46 08             movq    8(%rsi), %rax
  100000fa0:      0f be 00                movsbl  (%rax), %eax
  100000fa3:      3b 04 25 48 00 00 00    cmpl    72, %eax
  100000faa:      0f 8c 07 00 00 00       jl      7 <.Lend>
  100000fb0:      2b 04 25 48 00 00 00    subl    72, %eax
  .Lend:
  100000fb7:      c3                      ret

And the (pretty verbose) generated YAML:

  ---
  Atoms:
    - StartAddress:    0x0000000100000F9C
      Size:            20
      Type:            Text
      Content:
        - Inst:            MOV64rm
          Size:            4
          Ops:             [ RRAX, RRSI, I1, R, I8, R ]
        - Inst:            MOVSX32rm8
          Size:            3
          Ops:             [ REAX, RRAX, I1, R, I0, R ]
        - Inst:            CMP32rm
          Size:            7
          Ops:             [ REAX, R, I1, R, I72, R ]
        - Inst:            JL_4
          Size:            6
          Ops:             [ I7 ]
    - StartAddress:    0x0000000100000FB0
      Size:            7
      Type:            Text
      Content:
        - Inst:            SUB32rm
          Size:            7
          Ops:             [ REAX, REAX, R, I1, R, I72, R ]
    - StartAddress:    0x0000000100000FB7
      Size:            1
      Type:            Text
      Content:
        - Inst:            RET
          Size:            1
          Ops:             [  ]
  Functions:
    - Name:            __text
      BasicBlocks:
        - Address:         0x0000000100000F9C
          Preds:           [  ]
          Succs:           [ 0x0000000100000FB7, 0x0000000100000FB0 ]
     <snip>
  ...

llvm-svn: 188890
2013-08-21 07:29:02 +00:00
Ahmed Bougacha aa79068157 MC: Disassembled CFG reconstruction.
This patch builds on some existing code to do CFG reconstruction from
a disassembled binary:
- MCModule represents the binary, and has a list of MCAtoms.
- MCAtom represents either disassembled instructions (MCTextAtom), or
  contiguous data (MCDataAtom), and covers a specific range of addresses.
- MCBasicBlock and MCFunction form the reconstructed CFG. An MCBB is
  backed by an MCTextAtom, and has the usual successors/predecessors.
- MCObjectDisassembler creates a module from an ObjectFile using a
  disassembler. It first builds an atom for each section. It can also
  construct the CFG, and this splits the text atoms into basic blocks.

MCModule and MCAtom were only sketched out; MCFunction and MCBB were
implemented under the experimental "-cfg" llvm-objdump -macho option.
This cleans them up for further use; llvm-objdump -d -cfg now generates
graphviz files for each function found in the binary.

In the future, MCObjectDisassembler may be the right place to do
"intelligent" disassembly: for example, handling constant islands is just
a matter of splitting the atom, using information that may be available
in the ObjectFile. Also, better initial atom formation than just using
sections is possible using symbols (and things like Mach-O's
function_starts load command).

This brings two minor regressions in llvm-objdump -macho -cfg:
- The printing of a relocation's referenced symbol.
- An annotation on loop BBs, i.e., which are their own successor.

Relocation printing is replaced by the MCSymbolizer; the basic CFG
annotation will be superseded by more related functionality.

llvm-svn: 182628
2013-05-24 01:07:04 +00:00
Ahmed Bougacha ad1084de84 Add MCSymbolizer for symbolic/annotated disassembly.
This is a basic first step towards symbolization of disassembled
instructions. This used to be done using externally provided (C API)
callbacks. This patch introduces:
- the MCSymbolizer class, that mimics the same functions that were used
  in the X86 and ARM disassemblers to symbolize immediate operands and
  to annotate loads based off PC (for things like c string literals).
- the MCExternalSymbolizer class, which implements the old C API.
- the MCRelocationInfo class, which provides a way for targets to
  translate relocations (either object::RelocationRef, or disassembler
  C API VariantKinds) to MCExprs.
- the MCObjectSymbolizer class, which does symbolization using what it
  finds in an object::ObjectFile. This makes simple symbolization (with
  no fancy relocation stuff) work for all object formats!
- x86-64 Mach-O and ELF MCRelocationInfos.
- A basic ARM Mach-O MCRelocationInfo, that provides just enough to
  support the C API VariantKinds.

Most of what works in otool (the only user of the old symbolization API
that I know of) for x86-64 symbolic disassembly (-tvV) works, namely:
- symbol references: call _foo; jmp 15 <_foo+50>
- relocations:       call _foo-_bar; call _foo-4
- __cf?string:       leaq 193(%rip), %rax ## literal pool for "hello"
Stub support is the main missing part (because libObject doesn't know,
among other things, about mach-o indirect symbols).

As for the MCSymbolizer API, instead of relying on the disassemblers
to call the tryAdding* methods, maybe this could be done automagically
using InstrInfo? For instance, even though PC-relative LEAs are used
to get the address of string literals in a typical Mach-O file, a MOV
would be used in an ELF file. And right now, the explicit symbolization
only recognizes PC-relative LEAs. InstrInfo should have already have
most of what is needed to know what to symbolize, so this can
definitely be improved.

I'd also like to remove object::RelocationRef::getValueString (it seems
only used by relocation printing in objdump), as simply printing the
created MCExpr is definitely enough (and cleaner than string concats).

llvm-svn: 182625
2013-05-24 00:39:57 +00:00
Roman Divacky ff95a1dc12 Remove MCTargetAsmLexer and its derived classes now that edis,
its only user, is gone.

llvm-svn: 170699
2012-12-20 14:43:30 +00:00
Jakob Stoklund Olesen 0c06121e4e Give MCRegisterInfo an implementation file.
Move some functions from MCRegisterInfo.h that don't need to be inline.

This shrinks llc by 8K.

llvm-svn: 160865
2012-07-27 16:25:20 +00:00
Rafael Espindola 5cb98f1062 Remove the logging streamer.
llvm-svn: 147820
2012-01-10 00:40:39 +00:00
Daniel Dunbar 539d0a8a09 build/CMake: Finish removal of add_llvm_library_dependencies.
llvm-svn: 145420
2011-11-29 19:25:30 +00:00
Benjamin Kramer f550fa9173 Sort CMakeLists.txt.
llvm-svn: 140465
2011-09-24 22:06:35 +00:00
Owen Anderson adea3f0c01 Add new files to CMake.
llvm-svn: 140352
2011-09-22 23:20:48 +00:00