[Coverage][WebAssembly] Add initial support for WebAssembly/WASI (#111332)

Currently, WebAssembly/WASI target does not provide direct support for
code coverage.
This patch set fixes several issues

[Coverage][WebAssembly] Add initial support for WebAssembly/WASI (#111332)

Currently, WebAssembly/WASI target does not provide direct support for
code coverage.
This patch set fixes several issues to unlock the feature. The main
changes are:

1. Port `compiler-rt/lib/profile` to WebAssembly/WASI.
2. Adjust profile metadata sections for Wasm object file format.
- [CodeGen] Emit `__llvm_covmap` and `__llvm_covfun` as custom sections
instead of data segments.
- [lld] Align the interval space of custom sections at link time.
- [llvm-cov] Copy misaligned custom section data if the start address is
not aligned.
- [llvm-cov] Read `__llvm_prf_names` from data segments
3. [clang] Link with profile runtime libraries if requested

See each commit message for more details and rationale.
This is part of the effort to add code coverage support in Wasm target
of Swift toolchain.

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[InstrProfiling] No runtime registration for ELF, COFF, Mach-O and XCOFF (#77225)

Whether runtime registration is needed is not dependent on the OS but
the file format. For ELF, COFF, Mach-O or XCO

[InstrProfiling] No runtime registration for ELF, COFF, Mach-O and XCOFF (#77225)

Whether runtime registration is needed is not dependent on the OS but
the file format. For ELF, COFF, Mach-O or XCOFF, we can always use the
linker support. This is important for baremetal platforms such as RTOS
and UEFI platforms where there is no OS but we still don't want to use
runtime registration and rely on linker support instead.

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[PGO][AIX] Improve dummy var retention and allow -bcdtors:csect linking.

1) Use a static array of pointer to retain the dummy vars.
2) Associate liveness of the array with that of the runtime hook v

[PGO][AIX] Improve dummy var retention and allow -bcdtors:csect linking.

1) Use a static array of pointer to retain the dummy vars.
2) Associate liveness of the array with that of the runtime hook variable
__llvm_profile_runtime.
3) Perform the runtime initialization through the runtime hook variable.
4) Preserve the runtime hook variable using the -u linker flag.

Reviewed By: hubert.reinterpretcast

Differential Revision: https://reviews.llvm.org/D136192

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[InstrProf] Set prof global variables to internal linkage if adding a comdat

COFF has a verifier check that private global variables don't have a comdat of the same name.

Reviewed By: rnk

Differen

[InstrProf] Set prof global variables to internal linkage if adding a comdat

COFF has a verifier check that private global variables don't have a comdat of the same name.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D131043

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

[InstrProf] Mark __llvm_profile_runtime hidden to match libclang_rt.profile definition

Mark the symbol hidden to match INSTR_PROF_PROFILE_RUNTIME_VAR in compiler-rt.

Fixes second issue discussed at

[InstrProf] Mark __llvm_profile_runtime hidden to match libclang_rt.profile definition

Mark the symbol hidden to match INSTR_PROF_PROFILE_RUNTIME_VAR in compiler-rt.

Fixes second issue discussed at https://discourse.llvm.org/t/63090

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D128842

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Reland "[PS4/PS5][profiling] Go back to the old way of doing a runtime hook"

Profiling stopped working for us after D98061, which was largely a
Fuschia-specific patch but in one place used `isOSBinF

Reland "[PS4/PS5][profiling] Go back to the old way of doing a runtime hook"

Profiling stopped working for us after D98061, which was largely a
Fuschia-specific patch but in one place used `isOSBinFormatELF` to
make a decision. I'm adding a PS4/PS5 exception to that, so we can
get profiling to work again.

Differential Revision: https://reviews.llvm.org/D127506

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Revert "[PS4/PS5][profiling] Go back to the old way of doing a runtime hook"

This reverts commit 39fb84343ec5cf9081e236745490c65eb8a9fc31.

Pushed without verifying the test still works.

[PS4/PS5][profiling] Go back to the old way of doing a runtime hook

Profiling stopped working for us after D98061, which was largely a
Fuschia-specific patch but in one place used `isOSBinFormatELF`

[PS4/PS5][profiling] Go back to the old way of doing a runtime hook

Profiling stopped working for us after D98061, which was largely a
Fuschia-specific patch but in one place used `isOSBinFormatELF` to
make a decision. I'm adding a PS4/PS5 exception to that, so we can
get profiling to work again.

Differential Revision: https://reviews.llvm.org/D127506

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[AIX][PGO] Enable linux style PGO on AIX

This patch switches the PGO implementation on AIX from using the runtime
registration-based section tracking to the __start_SECNAME/__stop_SECNAME
based. In

[AIX][PGO] Enable linux style PGO on AIX

This patch switches the PGO implementation on AIX from using the runtime
registration-based section tracking to the __start_SECNAME/__stop_SECNAME
based. In order to enable the recognition of __start_SECNAME/__stop_SECNAME
symbols in the AIX linker, the -bdbg:namedsects:ss needs to be used.

Reviewed By: jsji, MaskRay, davidxl

Differential Revision: https://reviews.llvm.org/D124857

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[AIX] Change the linkage of profiling counter/data to be private

We generate symbols like `profc`/`profd` for each function, and put them into csects.
When there are weak functions, we generate wea

[AIX] Change the linkage of profiling counter/data to be private

We generate symbols like `profc`/`profd` for each function, and put them into csects.
When there are weak functions, we generate weak symbols for the functions as well,
with ELF (and some others), linker (binder) will discard and only keep one copy of the weak symbols.

However, on AIX, the current binder can NOT discard the weak symbols if we put all of them into the same csect,
as binder can NOT discard a subset of a csect.

This creates a unique challenge for using those symbols to calculate some relative offsets.

This patch changed the linkage of `profc`/`profd` symbols to be private, so that all the profc/profd for each weak symbol will be *local* to objects, and all kept in the csect, so we won't have problem. Although only one of the counters will be used, all the pointer in the profd is correct.

The downside is that we won't be able to discard the duplicated counters and profile data,
but those can not be discarded even if we keep the weak linkage,
due to the binder limitation of not discarding a subsect of the csect either .

Reviewed By: Whitney, MaskRay

Differential Revision: https://reviews.llvm.org/D110422

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[InstrProfiling] Add one missing XCOFF line to profiling.ll

[InstrProfiling] Add AIX triple to more tests

Following patch of https://reviews.llvm.org/D108490.
Add AIX triples to tests in /Instrumentation/InstrProfiling/ to make
sure we can catch regressions

[InstrProfiling] Add AIX triple to more tests

Following patch of https://reviews.llvm.org/D108490.
Add AIX triples to tests in /Instrumentation/InstrProfiling/ to make
sure we can catch regressions earlier.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D109089

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[InstrProfiling] Use llvm.compiler.used if applicable for Mach-O

Similar to D97585.

D25456 used `S_ATTR_LIVE_SUPPORT` to ensure the data variable will be retained
or discarded as a unit with the co

[InstrProfiling] Use llvm.compiler.used if applicable for Mach-O

Similar to D97585.

D25456 used `S_ATTR_LIVE_SUPPORT` to ensure the data variable will be retained
or discarded as a unit with the counter variable, so llvm.compiler.used is
sufficient. It allows ld to dead strip unneeded profc and profd variables.

Reviewed By: vsk

Differential Revision: https://reviews.llvm.org/D105445

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[InstrProfiling][test] Combine profiling.ll and linkage.ll

The latter mostly covers the former.

Revert "[InstrProfiling] Make COFF use the ELF comdat scheme (drop link.exe compatibility)"

This reverts commit fbb8e772ec501a1b71643db90e9c6445e17d7cac.

Accidentally pushed.

[InstrProfiling] Make COFF use the ELF comdat scheme (drop link.exe compatibility)

The COFF specific `DataReferencedByCode` complexity (D103372 D103717) is due to
a link.exe limitation: an external

[InstrProfiling] Make COFF use the ELF comdat scheme (drop link.exe compatibility)

The COFF specific `DataReferencedByCode` complexity (D103372 D103717) is due to
a link.exe limitation: an external symbol in IMAGE_COMDAT_SELECT_ASSOCIATIVE is
not really dropped, so it can cause duplicate definition error.

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[InstrProfiling] Generate runtime hook for Fuchsia

When none of the translation units in the binary have been instrumented
we shouldn't need to link the profile runtime. However, because we pass
-u_

[InstrProfiling] Generate runtime hook for Fuchsia

When none of the translation units in the binary have been instrumented
we shouldn't need to link the profile runtime. However, because we pass
-u__llvm_profile_runtime on Linux and Fuchsia, the runtime would still
be pulled in and incur some overhead. On Fuchsia which uses runtime
counter relocation, it also means that we cannot reference the bias
variable unconditionally.

This change modifies the InstrProfiling pass to pull in the profile
runtime only when needed by declaring the __llvm_profile_runtime symbol
in the translation unit only when needed. For now we restrict this only
for Fuchsia, but this can be later expanded to other platforms. This
approach was already used prior to 9a041a75221ca, but we changed it
to always generate the __llvm_profile_runtime due to a TAPI limitation,
but that limitation may no longer apply, and it certainly doesn't apply
on platforms like Fuchsia.

Differential Revision: https://reviews.llvm.org/D98061

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[InstrProfiling] Make CountersPtr in __profd_ relative

Change `CountersPtr` in `__profd_` to a label difference, which is a link-time
constant. On ELF, when linking a shared object, this requires th

[InstrProfiling] Make CountersPtr in __profd_ relative

Change `CountersPtr` in `__profd_` to a label difference, which is a link-time
constant. On ELF, when linking a shared object, this requires that `__profc_` is
either private or linkonce/linkonce_odr hidden. On COFF, we need D104564 so that
`.quad a-b` (64-bit label difference) can lower to a 32-bit PC-relative relocation.

```
# ELF: R_X86_64_PC64 (PC-relative)
.quad .L__profc_foo-.L__profd_foo

# Mach-O: a pair of 8-byte X86_64_RELOC_UNSIGNED and X86_64_RELOC_SUBTRACTOR
.quad l___profc_foo-l___profd_foo

# COFF: we actually use IMAGE_REL_AMD64_REL32/IMAGE_REL_ARM64_REL32 so
# the high 32-bit value is zero even if .L__profc_foo < .L__profd_foo
# As compensation, we truncate CountersDelta in the header so that
# __llvm_profile_merge_from_buffer and llvm-profdata reader keep working.
.quad .L__profc_foo-.L__profd_foo
```

(Note: link.exe sorts `.lprfc` before `.lprfd` even if the object writer
has `.lprfd` before `.lprfc`, so we cannot work around by reordering
`.lprfc` and `.lprfd`.)

With this change, a stage 2 (`-DLLVM_TARGETS_TO_BUILD=X86 -DLLVM_BUILD_INSTRUMENTED=IR`)
`ld -pie` linked clang is 1.74% smaller due to fewer R_X86_64_RELATIVE relocations.
```
% readelf -r pie | awk '$3~/R.*/{s[$3]++} END {for (k in s) print k, s[k]}'
R_X86_64_JUMP_SLO 331
R_X86_64_TPOFF64 2
R_X86_64_RELATIVE 476059 # was: 607712
R_X86_64_64 2616
R_X86_64_GLOB_DAT 31
```

The absolute function address (used by llvm-profdata to collect indirect call
targets) can be converted to relative as well, but is not done in this patch.

Differential Revision: https://reviews.llvm.org/D104556

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[InstrProfiling] If no value profiling, make data variable private and (for Windows) use one comdat

`__profd_*` variables are referenced by code only when value profiling is
enabled. If disabled (e.

[InstrProfiling] If no value profiling, make data variable private and (for Windows) use one comdat

`__profd_*` variables are referenced by code only when value profiling is
enabled. If disabled (e.g. default -fprofile-instr-generate), the symbols just
waste space on ELF/Mach-O. We change the comdat symbol from `__profd_*` to
`__profc_*` because an internal symbol does not provide deduplication features
on COFF. The choice doesn't matter on ELF.

(In -DLLVM_BUILD_INSTRUMENTED_COVERAGE=on build, there is now no `__profd_*` symbols.)

On Windows this enables further optimization. We are no longer affected by the
link.exe limitation: an external symbol in IMAGE_COMDAT_SELECT_ASSOCIATIVE can
cause duplicate definition error.
https://lists.llvm.org/pipermail/llvm-dev/2021-May/150758.html
We can thus use llvm.compiler.used instead of llvm.used like ELF (D97585).
This avoids many `/INCLUDE:` directives in `.drectve`.

Here is rnk's measurement for Chrome:
```
This reduced object file size of base_unittests.exe, compiled with coverage, optimizations, and gmlt debug info by 10%:

#BEFORE

$ find . -iname '*.obj' | xargs du -b | awk '{ sum += $1 } END { print sum}'
1047758867

$ du -cksh base_unittests.exe
82M base_unittests.exe
82M total

# AFTER

$ find . -iname '*.obj' | xargs du -b | awk '{ sum += $1 } END { print sum}'
937886499

$ du -cksh base_unittests.exe
78M base_unittests.exe
78M total
```

The change is NFC for Mach-O.

Reviewed By: davidxl, rnk

Differential Revision: https://reviews.llvm.org/D103372

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Revert "[InstrProfiling] If no value profiling, make data variable private and (for Windows) use one comdat"

This reverts commit a14fc749aab2c8e1a45d19d512255ebfc69357c3.
Breaks check-profile on mac

Revert "[InstrProfiling] If no value profiling, make data variable private and (for Windows) use one comdat"

This reverts commit a14fc749aab2c8e1a45d19d512255ebfc69357c3.
Breaks check-profile on macOS. See https://reviews.llvm.org/D103372 for details.

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[InstrProfiling] If no value profiling, make data variable private and (for Windows) use one comdat

`__profd_*` variables are referenced by code only when value profiling is
enabled. If disabled (e.

[InstrProfiling] If no value profiling, make data variable private and (for Windows) use one comdat

`__profd_*` variables are referenced by code only when value profiling is
enabled. If disabled (e.g. default -fprofile-instr-generate), the symbols just
waste space on ELF/Mach-O. We change the comdat symbol from `__profd_*` to
`__profc_*` because an internal symbol does not provide deduplication features
on COFF. The choice doesn't matter on ELF.

(In -DLLVM_BUILD_INSTRUMENTED_COVERAGE=on build, there is now no `__profd_*` symbols.)

On Windows this enables further optimization. We are no longer affected by the
link.exe limitation: an external symbol in IMAGE_COMDAT_SELECT_ASSOCIATIVE can
cause duplicate definition error.
https://lists.llvm.org/pipermail/llvm-dev/2021-May/150758.html
We can thus use llvm.compiler.used instead of llvm.used like ELF (D97585).
This avoids many `/INCLUDE:` directives in `.drectve`.

Here is rnk's measurement for Chrome:
```
This reduced object file size of base_unittests.exe, compiled with coverage, optimizations, and gmlt debug info by 10%:

#BEFORE

$ find . -iname '*.obj' | xargs du -b | awk '{ sum += $1 } END { print sum}'
1047758867

$ du -cksh base_unittests.exe
82M base_unittests.exe
82M total

# AFTER

$ find . -iname '*.obj' | xargs du -b | awk '{ sum += $1 } END { print sum}'
937886499

$ du -cksh base_unittests.exe
78M base_unittests.exe
78M total
```

Reviewed By: davidxl, rnk

Differential Revision: https://reviews.llvm.org/D103372

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[InstrProfiling] Delete linkage/visibility toggling for Windows

The linkage/visibility of `__profn_*` variables are derived
from the profiled functions.

extern_weak => linkonce
available_ex

[InstrProfiling] Delete linkage/visibility toggling for Windows

The linkage/visibility of `__profn_*` variables are derived
from the profiled functions.

extern_weak => linkonce
available_externally => linkonce_odr
internal => private
extern => private
_ => unchanged

The linkage/visibility of `__profc_*`/`__profd_*` variables are derived from
`__profn_*` with linkage/visibility wrestling for Windows.

The changes can be folded to the following without changing semantics.

```
if (TT.isOSBinFormatCOFF() && !NeedComdat) {
Linkage = GlobalValue::InternalLinkage;
Visibility = GlobalValue::DefaultVisibility;
}
```

That said, I think we can just delete the code block.

An extern/internal function will now use private `__profc_*`/`__profd_*`
variables, instead of internal ones. This saves some symbol table entries.

A non-comdat {linkonce,weak}_odr function will now use hidden external
`__profc_*`/`__profd_*` variables instead of internal ones. There is potential
object file size increase because such symbols need `/INCLUDE:` directives.
However such non-comdat functions are rare (note that non-comdat weak
definitions don't prevent duplicate definition error).

The behavior changes match ELF.

Reviewed By: rnk

Differential Revision: https://reviews.llvm.org/D103355

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[InstrProfiling][test] Improve tests

[InstrProfiling][test] Fix stale tests

* Change linkage/visibility of __profn_ variables to match the reality
* alwaysinline.ll: Add "EnableValueProfiling", otherwise it doesn't test available_exter

[InstrProfiling][test] Fix stale tests

* Change linkage/visibility of __profn_ variables to match the reality
* alwaysinline.ll: Add "EnableValueProfiling", otherwise it doesn't test available_externally alwaysinline.
* Delete PR23499.ll - covered by other comdat tests.

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