Reland "[TypeProf][InstrPGO] Introduce raw and instr profile format change for type profiling." (#82711)

New change on top of [reviewed
patch](https://github.com/llvm/llvm-project/pull/81691) are [

Reland "[TypeProf][InstrPGO] Introduce raw and instr profile format change for type profiling." (#82711)

New change on top of [reviewed
patch](https://github.com/llvm/llvm-project/pull/81691) are [in commits
after this
one](https://github.com/llvm/llvm-project/pull/82711/commits/d0757f46b3e3865b5f7c552bc0744309a363e0ac).
Previous commits are restored from the remote branch with timestamps.

1. Fix build breakage for non-ELF platforms, by defining the missing
functions {`__llvm_profile_begin_vtables`, `__llvm_profile_end_vtables`,
`__llvm_profile_begin_vtabnames `, `__llvm_profile_end_vtabnames`}
everywhere.
* Tested on mac laptop (for darwins) and Windows. Specifically,
functions in `InstrProfilingPlatformWindows.c` returns `NULL` to make it
more explicit that type prof isn't supported; see comments for the
reason.
* For the rest (AIX, other), mostly follow existing examples (like this
[one](https://github.com/llvm/llvm-project/commit/f95b2f1acf1171abb0d00089fd4c9238753847e3))

2. Rename `__llvm_prf_vtabnames` -> `__llvm_prf_vns` for shorter section
name, and make returned pointers
[const](https://github.com/llvm/llvm-project/pull/82711/commits/a825d2a4ec00f07772a373091a702f149c3b0c34#diff-4de780ce726d76b7abc9d3353aef95013e7b21e7bda01be8940cc6574fb0b5ffR120-R121)

**Original Description**

* Raw profile format
- Header: records the byte size of compressed vtable names, and the
number of profiled vtable entries (call it `VTableProfData`). Header
also records padded bytes of each section.
- Payload: adds a section for compressed vtable names, and a section to
store `VTableProfData`. Both sections are padded so the size is a
multiple of 8.
* Indexed profile format
- Header: records the byte offset of compressed vtable names.
- Payload: adds a section to store compressed vtable names. This section
is used by `llvm-profdata` to show the list of vtables profiled for an
instrumented site.

[The originally reviewed
patch](https://github.com/llvm/llvm-project/pull/66825) will have
profile reader/write change and llvm-profdata change.
- To ensure this PR has all the necessary profile format change along
with profile version bump, created a copy of the originally reviewed
patch in https://github.com/llvm/llvm-project/pull/80761. The copy
doesn't have profile format change, but it has the set of tests which
covers type profile generation, profile read and profile merge. Tests
pass there.

rfc in
https://discourse.llvm.org/t/rfc-dynamic-type-profiling-and-optimizations-in-llvm/74600

---------

Co-authored-by: modiking <modiking213@gmail.com>

show more ...

Revert type profiling change as compiler-rt test break on Windows. (#82583)

Examples
https://lab.llvm.org/buildbot/#/builders/127/builds/62532/steps/8/logs/stdio

[TypeProf][InstrPGO] Introduce raw and instr profile format change for type profiling. (#81691)

* Raw profile format
- Header: records the byte size of compressed vtable names, and the
number of p

[TypeProf][InstrPGO] Introduce raw and instr profile format change for type profiling. (#81691)

* Raw profile format
- Header: records the byte size of compressed vtable names, and the
number of profiled vtable entries (call it `VTableProfData`). Header
also records padded bytes of each section.
- Payload: adds a section for compressed vtable names, and a section to
store `VTableProfData`. Both sections are padded so the size is a
multiple of 8.
* Indexed profile format
- Header: records the byte offset of compressed vtable names.
- Payload: adds a section to store compressed vtable names. This section
is used by `llvm-profdata` to show the list of vtables profiled for an
instrumented site.

[The originally reviewed
patch](https://github.com/llvm/llvm-project/pull/66825) will have
profile reader/write change and llvm-profdata change.
- To ensure this PR has all the necessary profile format change along
with profile version bump, created a copy of the originally reviewed
patch in https://github.com/llvm/llvm-project/pull/80761. The copy
doesn't have profile format change, but it has the set of tests which
covers type profile generation, profile read and profile merge. Tests
pass there.

rfc in
https://discourse.llvm.org/t/rfc-dynamic-type-profiling-and-optimizations-in-llvm/74600

---------

Co-authored-by: modiking <modiking213@gmail.com>

show more ...

[Profile] Add binary profile correlation for code coverage. (#69493)

## Motivation
Since we don't need the metadata sections at runtime, we can somehow
offload them from memory at runtime. Initial

[Profile] Add binary profile correlation for code coverage. (#69493)

## Motivation
Since we don't need the metadata sections at runtime, we can somehow
offload them from memory at runtime. Initially, I explored [debug info
correlation](https://discourse.llvm.org/t/instrprofiling-lightweight-instrumentation/59113),
which is used for PGO with value profiling disabled. However, it
currently only works with DWARF and it's be hard to add such artificial
debug info for every function in to CodeView which is used on Windows.
So, offloading profile metadata sections at runtime seems to be a
platform independent option.

## Design
The idea is to use new section names for profile name and data sections
and mark them as metadata sections. Under this mode, the new sections
are non-SHF_ALLOC in ELF. So, they are not loaded into memory at runtime
and can be stripped away as a post-linking step. After the process
exits, the generated raw profiles will contains only headers + counters.
llvm-profdata can be used correlate raw profiles with the unstripped
binary to generate indexed profile.

## Data
For chromium base_unittests with code coverage on linux, the binary size
overhead due to instrumentation reduced from 64M to 38.8M (39.4%) and
the raw profile files size reduce from 128M to 68M (46.9%)
```
$ bloaty out/cov/base_unittests.stripped -- out/no-cov/base_unittests.stripped
FILE SIZE VM SIZE
-------------- --------------
+121% +30.4Mi +121% +30.4Mi .text
[NEW] +14.6Mi [NEW] +14.6Mi __llvm_prf_data
[NEW] +10.6Mi [NEW] +10.6Mi __llvm_prf_names
[NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts
+95% +1.75Mi +95% +1.75Mi .eh_frame
+108% +400Ki +108% +400Ki .eh_frame_hdr
+9.5% +211Ki +9.5% +211Ki .rela.dyn
+9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro
+5.0% +87.3Ki +5.0% +87.3Ki .rodata
[ = ] 0 +13% +47.0Ki .bss
+40% +1.78Ki +40% +1.78Ki .got
+12% +1.49Ki +12% +1.49Ki .gcc_except_table
[ = ] 0 +65% +1.23Ki .relro_padding
+62% +1.20Ki [ = ] 0 [Unmapped]
+13% +448 +19% +448 .init_array
+8.8% +192 [ = ] 0 [ELF Section Headers]
+0.0% +136 +0.0% +80 [7 Others]
+0.1% +96 +0.1% +96 .dynsym
+1.2% +96 +1.2% +96 .rela.plt
+1.5% +80 +1.2% +64 .plt
[ = ] 0 -99.2% -3.68Ki [LOAD #5 [RW]]
+195% +64.0Mi +194% +64.0Mi TOTAL
$ bloaty out/cov-cor/base_unittests.stripped -- out/no-cov/base_unittests.stripped
FILE SIZE VM SIZE
-------------- --------------
+121% +30.4Mi +121% +30.4Mi .text
[NEW] +5.86Mi [NEW] +5.86Mi __llvm_prf_cnts
+95% +1.75Mi +95% +1.75Mi .eh_frame
+108% +400Ki +108% +400Ki .eh_frame_hdr
+9.5% +211Ki +9.5% +211Ki .rela.dyn
+9.2% +95.0Ki +9.2% +95.0Ki .data.rel.ro
+5.0% +87.3Ki +5.0% +87.3Ki .rodata
[ = ] 0 +13% +47.0Ki .bss
+40% +1.78Ki +40% +1.78Ki .got
+12% +1.49Ki +12% +1.49Ki .gcc_except_table
+13% +448 +19% +448 .init_array
+0.1% +96 +0.1% +96 .dynsym
+1.2% +96 +1.2% +96 .rela.plt
+1.2% +64 +1.2% +64 .plt
+2.9% +64 [ = ] 0 [ELF Section Headers]
+0.0% +40 +0.0% +40 .data
+1.2% +32 +1.2% +32 .got.plt
+0.0% +24 +0.0% +8 [5 Others]
[ = ] 0 -22.9% -872 [LOAD #5 [RW]]
-74.5% -1.44Ki [ = ] 0 [Unmapped]
[ = ] 0 -76.5% -1.45Ki .relro_padding
+118% +38.8Mi +117% +38.8Mi TOTAL
```

A few things to note:
1. llvm-profdata doesn't support filter raw profiles by binary id yet,
so when a raw profile doesn't belongs to the binary being digested by
llvm-profdata, merging will fail. Once this is implemented,
llvm-profdata should be able to only merge raw profiles with the same
binary id as the binary and discard the rest (with mismatched/missing
binary id). The workflow I have in mind is to have scripts invoke
llvm-profdata to get all binary ids for all raw profiles, and
selectively choose the raw pnrofiles with matching binary id and the
binary to llvm-profdata for merging.
2. Note: In COFF, currently they are still loaded into memory but not
used. I didn't do it in this patch because I noticed that `.lcovmap` and
`.lcovfunc` are loaded into memory. A separate patch will address it.
3. This should works with PGO when value profiling is disabled as debug
info correlation currently doing, though I haven't tested this yet.

show more ...

[PGO][InstrProf][test] Convert to opaque pointers and fix some stale tests

[test] Migrate legacy InstrProfiling tests to new PM

[InstrProf] Add single byte coverage mode

Use the llvm flag `-pgo-function-entry-coverage` to create single byte "counters" to track functions coverage. This mode has significantly less size overhea

[InstrProf] Add single byte coverage mode

Use the llvm flag `-pgo-function-entry-coverage` to create single byte "counters" to track functions coverage. This mode has significantly less size overhead in both code and data because
* We mark a function as "covered" with a store instead of an increment which generally requires fewer assembly instructions
* We use a single byte per function rather than 8 bytes per block

The trade off of course is that this mode only tells you if a function has been covered. This is useful, for example, to detect dead code.

When combined with debug info correlation [0] we are able to create an instrumented Clang binary that is only 150M (the vanilla Clang binary is 143M). That is an overhead of 7M (4.9%) compared to the default instrumentation (without value profiling) which has an overhead of 31M (21.7%).

[0] https://groups.google.com/g/llvm-dev/c/r03Z6JoN7d4

Reviewed By: kyulee

Differential Revision: https://reviews.llvm.org/D116180

show more ...