Coverage: Document how to collect a profile without a filesystem

The profiling runtime was designed to work without static initializers
or a a filesystem (see 117cf2bd1ff585f9754b5f30f5a4cfd65b230bb

Coverage: Document how to collect a profile without a filesystem

The profiling runtime was designed to work without static initializers
or a a filesystem (see 117cf2bd1ff585f9754b5f30f5a4cfd65b230bbf and
others). The no-static-initializers part was already documented but this
part got missed before.

Differential Revision: https://reviews.llvm.org/D101000

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[docs/Coverage] Document -show-region-summary

As a drive-by, fix the section in the clang docs about the number of
statistics visible in a report.

[docs/Coverage] Answer FAQ about optimization

Revert "Support for instrumenting only selected files or functions"

This reverts commit 4edf35f11a9e20bd5df3cb47283715f0ff38b751 because
the test fails on Windows bots.

Support for instrumenting only selected files or functions

This change implements support for applying profile instrumentation
only to selected files or functions. The implementation uses the
saniti

Support for instrumenting only selected files or functions

This change implements support for applying profile instrumentation
only to selected files or functions. The implementation uses the
sanitizer special case list format to select which files and functions
to instrument, and relies on the new noprofile IR attribute to exclude
functions from instrumentation.

Differential Revision: https://reviews.llvm.org/D94820

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[Coverage] Add support for Branch Coverage in LLVM Source-Based Code Coverage

This is an enhancement to LLVM Source-Based Code Coverage in clang to track how
many times individual branch-generating

[Coverage] Add support for Branch Coverage in LLVM Source-Based Code Coverage

This is an enhancement to LLVM Source-Based Code Coverage in clang to track how
many times individual branch-generating conditions are taken (evaluate to TRUE)
and not taken (evaluate to FALSE). Individual conditions may comprise larger
boolean expressions using boolean logical operators. This functionality is
very similar to what is supported by GCOV except that it is very closely
anchored to the ASTs.

Differential Revision: https://reviews.llvm.org/D84467

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[profile] Add %t LLVM_PROFILE_FILE option to substitute $TMPDIR

Add support for expanding the %t filename specifier in LLVM_PROFILE_FILE
to the TMPDIR environment variable. This is supported on all

[profile] Add %t LLVM_PROFILE_FILE option to substitute $TMPDIR

Add support for expanding the %t filename specifier in LLVM_PROFILE_FILE
to the TMPDIR environment variable. This is supported on all platforms.

On Darwin, TMPDIR is used to specify a temporary application-specific
scratch directory. When testing apps on remote devices, it can be
challenging for the host device to determine the correct TMPDIR, so it's
helpful to have the runtime do this work.

rdar://68524185

Differential Revision: https://reviews.llvm.org/D87332

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fix some typos to cycle bots

[profile] Support counter relocation at runtime

This is an alternative to the continous mode that was implemented in
D68351. This mode relies on padding and the ability to mmap a file over
the exist

[profile] Support counter relocation at runtime

This is an alternative to the continous mode that was implemented in
D68351. This mode relies on padding and the ability to mmap a file over
the existing mapping which is generally only available on POSIX systems
and isn't suitable for other platforms.

This change instead introduces the ability to relocate counters at
runtime using a level of indirection. On every counter access, we add a
bias to the counter address. This bias is stored in a symbol that's
provided by the profile runtime and is initially set to zero, meaning no
relocation. The runtime can mmap the profile into memory at abitrary
location, and set bias to the offset between the original and the new
counter location, at which point every subsequent counter access will be
to the new location, which allows updating profile directly akin to the
continous mode.

The advantage of this implementation is that doesn't require any special
OS support. The disadvantage is the extra overhead due to additional
instructions required for each counter access (overhead both in terms of
binary size and performance) plus duplication of counters (i.e. one copy
in the binary itself and another copy that's mmapped).

Differential Revision: https://reviews.llvm.org/D69740

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[Coverage] Emit a gap region to cover switch bodies

Emit a gap region beginning where the switch body begins. This sets line
execution counts in the areas between non-overlapping cases to 0.

This a

[Coverage] Emit a gap region to cover switch bodies

Emit a gap region beginning where the switch body begins. This sets line
execution counts in the areas between non-overlapping cases to 0.

This also removes some special handling of the first case in a switch:
these are now treated like any other case.

This does not resolve an outstanding issue with case statement regions
that do not end when a region is terminated. But it should address
llvm.org/PR44011.

Differential Revision: https://reviews.llvm.org/D70571

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[profile] Support online merging with continuous sync mode

Make it possible to use online profile merging ("%m" mode) with
continuous sync ("%c" mode).

To implement this, the merged profile is lock

[profile] Support online merging with continuous sync mode

Make it possible to use online profile merging ("%m" mode) with
continuous sync ("%c" mode).

To implement this, the merged profile is locked in the runtime
initialization step and either a) filled out for the first time or b)
checked for compatibility. Then, the profile can simply be mmap()'d with
MAP_SHARED set. With the mmap() in place, counter updates from every
process which uses an image are mapped onto the same set of physical
pages assigned by the filesystem cache. After the mmap() is set up, the
profile is unlocked.

Differential Revision: https://reviews.llvm.org/D69586

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[profile] Add a mode to continuously sync counter updates to a file

Add support for continuously syncing profile counter updates to a file.

The motivation for this is that programs do not always ex

[profile] Add a mode to continuously sync counter updates to a file

Add support for continuously syncing profile counter updates to a file.

The motivation for this is that programs do not always exit cleanly. On
iOS, for example, programs are usually killed via a signal from the OS.
Running atexit() handlers after catching a signal is unreliable, so some
method for progressively writing out profile data is necessary.

The approach taken here is to mmap() the `__llvm_prf_cnts` section onto
a raw profile. To do this, the linker must page-align the counter and
data sections, and the runtime must ensure that counters are mapped to a
page-aligned offset within a raw profile.

Continuous mode is (for the moment) incompatible with the online merging
mode. This limitation is lifted in https://reviews.llvm.org/D69586.

Continuous mode is also (for the moment) incompatible with value
profiling, as I'm not sure whether there is interest in this and the
implementation may be tricky.

As I have not been able to test extensively on non-Darwin platforms,
only Darwin support is included for the moment. However, continuous mode
may "just work" without modification on Linux and some UNIX-likes. AIUI
the default value for the GNU linker's `--section-alignment` flag is set
to the page size on many systems. This appears to be true for LLD as
well, as its `no_nmagic` option is on by default. Continuous mode will
not "just work" on Fuchsia or Windows, as it's not possible to mmap() a
section on these platforms. There is a proposal to add a layer of
indirection to the profile instrumentation to support these platforms.

rdar://54210980

Differential Revision: https://reviews.llvm.org/D68351

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Update our URLs in clang doc to use https

llvm-svn: 346101

[docs] Coverage: Improve the wording a bit

llvm-svn: 305745

[docs] Coverage: document issue with the BFD linker

llvm-svn: 305743

[docs] coverage: Clarify which flags enable gcov-style profiling (NFC)

Point out that --coverage and -ftest-coverage, which is what most people
are used to, do not enable clang's frontend based cove

[docs] coverage: Clarify which flags enable gcov-style profiling (NFC)

Point out that --coverage and -ftest-coverage, which is what most people
are used to, do not enable clang's frontend based coverage pass.

Suggested by Benn Bolay!

llvm-svn: 294626

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Clarify how to forward-declare __llvm_profile symbols.

llvm-svn: 293065

[docs] Touch up the coverage docs some more

llvm-svn: 282169

[docs] Extend the code coverage docs some more

Flesh out the section on interpreting coverage reports, mention the
coverage export feature, and add notes on how to build llvm with
coverage turned on

[docs] Extend the code coverage docs some more

Flesh out the section on interpreting coverage reports, mention the
coverage export feature, and add notes on how to build llvm with
coverage turned on.

llvm-svn: 281988

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[docs] Touch up the code coverage doc

llvm-svn: 281881

[docs] Coverage: Reference the new -output-dir option

llvm-svn: 277081

[docs] Mention some new options in llvm-cov

llvm-svn: 277080

fix two typos in the doc

llvm-svn: 274447

[Docs] More warning fixes to unbreak the docs buildbot.

A number of warnings still remain, but these were the last of the
"unlexable code"-related ones (AFAICT).

I changed a few examples in docs/Us

[Docs] More warning fixes to unbreak the docs buildbot.

A number of warnings still remain, but these were the last of the
"unlexable code"-related ones (AFAICT).

I changed a few examples in docs/UsersManual.rst to showcase
-Wextra-tokens because it's already documented (-Wmultichar isn't), and
the sphinx C lexer apparently can't handle char literals like 'ab'. It
seemed like a better overall approach than just marking the code blocks
as none or console.

llvm-svn: 273232

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[docs] Coverage: Document the profile merge pool specifier

llvm-svn: 272604