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
This is a follow up to D118101, that added bexpfull to the test on instrprof-get-filename-merge-mode.c AIX, in order to get the
necessary symbols exported. But unfortunately the extra dependent symbols this exports actually cause segfaults, which is why
this isn't really recommended in the first place, so just use an actual export list.
Differential Revision: https://reviews.llvm.org/D118310
Use the `llvm-profdata show` command to verify debug info for profile correlation using the `--debug-info` option.
Reviewed By: kyulee
Differential Revision: https://reviews.llvm.org/D118181
There is no need to compress the names string when correlating with
debug info since InstrProfReader will immediately uncompress it anyway.
This also removes the dependency on zlib in this case.
Reviewed By: kyulee
Differential Revision: https://reviews.llvm.org/D118176
The AIX linker doesn't export any symbols by default, so an export list is usually used. Since clang doesn't have the tools to auto-generate an export list yet, just pass the linker an extra opt to tell it to export everything. This is generally not recommended for real shared libs, but is fine for the purpose of this test.
Differential Revision: https://reviews.llvm.org/D118101
Existing code tended to assume that counters had type `uint64_t` and
computed size from the number of counters. Fix this code to directly
compute the counters size in number of bytes where possible. When the
number of counters is needed, use `__llvm_profile_counter_entry_size()`
or `getCounterTypeSize()`. In a later diff these functions will depend
on the profile mode.
Change the meaning of `DataSize` and `CountersSize` to make them more clear.
* `DataSize` (`CountersSize`) - the size of the data (counter) section in bytes.
* `NumData` (`NumCounters`) - the number of data (counter) entries.
Reviewed By: kyulee
Differential Revision: https://reviews.llvm.org/D116179
When using debug info for profile correlation, avoid adding duplicate
functions in the synthetic Data section.
Before this patch, n duplicate function entries in the Data section would
cause counter values to be a factor of n larger. I built instrumented
clang with and without debug info correlation and got these summaries.
```
# With Debug Info Correlate
$ llvm-profdata show default.profdata
Instrumentation level: IR entry_first = 0
Total functions: 182530
Maximum function count: 52034
Maximum internal block count: 5763
# Without
$ llvm-profdata show default.profdata
Instrumentation level: IR entry_first = 0
Total functions: 183212
Maximum function count: 52034
Maximum internal block count: 5766
```
The slight difference in counts seem to be mostly from FileSystem and
Map functions and the difference in the number of instrumented functions
seems to come from missing debug info like destructors without source.
Reviewed By: kyulee
Differential Revision: https://reviews.llvm.org/D116051
There was a build failure on the `instrprof-debug-info-correlate.c` test
because zlib was missing so we need to require it to run the test.
Differential Revision: https://reviews.llvm.org/D115970
Extend `llvm-profdata` to read in a `.proflite` file and also a debug info file to generate a normal `.profdata` profile. This reduces the binary size by 8.4% when building an instrumented Clang binary without value profiling (164 MB vs 179 MB).
This work is part of the "lightweight instrumentation" RFC: https://groups.google.com/g/llvm-dev/c/r03Z6JoN7d4
This was first landed in https://reviews.llvm.org/D114566 but had to be reverted due to build errors.
Reviewed By: kyulee
Differential Revision: https://reviews.llvm.org/D115915
Extend `llvm-profdata` to read in a `.proflite` file and also a debug info file to generate a normal `.profdata` profile. This reduces the binary size by 8.4% when building an instrumented Clang binary without value profiling (164 MB vs 179 MB).
This work is part of the "lightweight instrumentation" RFC: https://groups.google.com/g/llvm-dev/c/r03Z6JoN7d4
Reviewed By: kyulee
Differential Revision: https://reviews.llvm.org/D114566
We are running `ls -lh` in gcov-execlp.c test in Posix folder.
However `-h` is not a POSIX option,ls on some POSIX system (eg: AIX)
may not support it.
This patch remove this option to avoid break.
Reviewed By: anhtuyen
Differential Revision: https://reviews.llvm.org/D111807
Some tests with binary IDs would fail with error: no profile can be merged.
This is because raw profiles could have unaligned headers when emitting binary
IDs. This means padding should be emitted after binary IDs are emitted to
ensure everything else is aligned. This patch adds padding after each binary ID
to ensure the next binary ID size is 8-byte aligned. This also adds extra
checks to ensure we aren't reading corrupted data when printing binary IDs.
Differential Revision: https://reviews.llvm.org/D110365
This test specifically checks that profiles are not mergeable if there's a
change in the CounterPtr in the profile header. The test manually changes
CounterPtr by explicitly calling memset on some offset into the profile file.
This test would fail if binary IDs were emitted because the offset calculation
does not take into account the binary ID sizes.
This patch updates the test to use types provided in profile/InstrProfData.inc
to make it more resistant to profile layout changes.
Differential Revision: https://reviews.llvm.org/D110277
We've been seeing this test return 31 instead of 32 for the "functions"
line in this test on our AArch64 bots.
One possible cause is some of the children not finishing in time
before the llvm-profdata commands are run, if the machine is heavily loaded.
Wait for all the children to finish before exiting the parent.
Reviewed By: zequanwu
Differential Revision: https://reviews.llvm.org/D109222
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
Newer Xcode toolchains ship a new otool implementation that prints out
section contents in a slightly different way than otool-classic. Specify
"-V" to otool to get the expected test output.
Differential Revision: https://reviews.llvm.org/D108929
Replace D107203, because __llvm_profile_set_file_object is usually used when the
process doesn't have permission to open/create file. That patch trying to copy
from old profile to new profile contradicts with the usage.
Differential Revision: https://reviews.llvm.org/D108242
This fixes support for merging profiles which broke as a consequence
of e50a38840dc3db5813f74b1cd2e10e6d984d0e67. The issue was missing
adjustment in merge logic to account for the binary IDs which are
now included in the raw profile just after header.
In addition, this change also:
* Includes the version in module signature that's used for merging
to avoid accidental attempts to merge incompatible profiles.
* Moves the binary IDs size field after version field in the header
as was suggested in the review.
Differential Revision: https://reviews.llvm.org/D107143
This fixes support for merging profiles which broke as a consequence
of e50a38840dc3db5813f74b1cd2e10e6d984d0e67. The issue was missing
adjustment in merge logic to account for the binary IDs which are
now included in the raw profile just after header.
In addition, this change also:
* Includes the version in module signature that's used for merging
to avoid accidental attempts to merge incompatible profiles.
* Moves the binary IDs size field after version field in the header
as was suggested in the review.
Differential Revision: https://reviews.llvm.org/D107143
This fixes support for merging profiles which broke as a consequence
of e50a38840dc3db5813f74b1cd2e10e6d984d0e67. The issue was missing
adjustment in merge logic to account for the binary IDs which are
now included in the raw profile just after header.
In addition, this change also:
* Includes the version in module signature that's used for merging
to avoid accidental attempts to merge incompatible profiles.
* Moves the binary IDs size field after version field in the header
as was suggested in the review.
Differential Revision: https://reviews.llvm.org/D107143
Revert "[profile] Change linkage type of a compiler-rt func"
This reverts commits f984ac2715f71c38a7872fa2c2ad535b3d4fa285 and
467c7191249b76abff33853b1692a77f327c2422 because it broke some builds.
The __llvm_prf_names section uses SHF_GNU_RETAIN. However, GNU ld before 2015-10
(https://sourceware.org/bugzilla/show_bug.cgi?id=19161) neither supports it nor
retains __llvm_prf_names according to __start___llvm_prf_names. So --gc-sections
does not work on such old GNU ld.
This is not a problem for gold and sufficiently new lld.
This mostly follows LLVM's InstrProfReader.cpp error handling.
Previously, attempting to merge corrupted profile data would result in
crashes. See https://crbug.com/1216811#c4.
Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D104050
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
This reduces the size of chrome.dll.pdb built with optimizations,
coverage, and line table info from 4,690,210,816 to 2,181,128,192, which
makes it possible to fit under the 4GB limit.
This change can greatly reduce binary size in coverage builds, which do
not need value profiling. IR PGO builds are unaffected. There is a minor
behavior change for frontend PGO.
PGO and coverage both use InstrProfiling to create profile data with
counters. PGO records the address of each function in the __profd_
global. It is used later to map runtime function pointer values back to
source-level function names. Coverage does not appear to use this
information.
Recording the address of every function with code coverage drastically
increases code size. Consider this program:
void foo();
void bar();
inline void inlineMe(int x) {
if (x > 0)
foo();
else
bar();
}
int getVal();
int main() { inlineMe(getVal()); }
With code coverage, the InstrProfiling pass runs before inlining, and it
captures the address of inlineMe in the __profd_ global. This greatly
increases code size, because now the compiler can no longer delete
trivial code.
One downside to this approach is that users of frontend PGO must apply
the -mllvm -enable-value-profiling flag globally in TUs that enable PGO.
Otherwise, some inline virtual method addresses may not be recorded and
will not be able to be promoted. My assumption is that this mllvm flag
is not popular, and most frontend PGO users don't enable it.
Differential Revision: https://reviews.llvm.org/D102818
If there are no counters, an mmap() of the counters section would fail
due to the size argument being too small (EINVAL).
rdar://78175925
Differential Revision: https://reviews.llvm.org/D102735
