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
I removed this test to unblock the ARM bots while looking into failures
(r374915), and am reinstating it now with a fix.
I believe the problem was that counter ptr address I used,
'\0\0\6\0\1\0\0\1', set the high bits of the pointer, not the low bits
like I wanted. On x86_64 this superficially looks like it tests r370826,
but it doesn't, as it would have been caught before r370826. However, on
ARM (or, 32-bit hosts more generally), I suspect the high bits were
cleared, and you get a 'valid' profile.
I verified that setting the *low* bits of the pointer does trigger the
new condition:
-// Note: The CounterPtr here is off-by-one. This should trigger a malformed profile error.
-RUN: printf '\0\0\6\0\1\0\0\1' >> %t.profraw
+// Note: The CounterPtr here is off-by-one.
+//
+// Octal '\11' is 9 in decimal: this should push CounterOffset to 1. As there are two counters,
+// the profile reader should error out.
+RUN: printf '\11\0\6\0\1\0\0\0' >> %t.profraw
This reverts commit c7cf5b3e4b918c9769fd760f28485b8d943ed968.
llvm-svn: 374927
There are a number arm bots failing after r374617 landed, and I'm not
sure why. It looks a bit like the error message llvm-profdata is
expected to print to stderr isn't flushed.
Weaken the test in an attempt to appease the arm bots: if this doesn't
work, that means that llvm-profdata is actually *not failing*, and that
will be a clear indication that some logic error is actually happening.
http://lab.llvm.org:8011/builders/clang-cmake-armv7-global-isel/builds/5604/
llvm-svn: 374792
The check needs to validate a counter offset before performing pointer
arithmetic with the (potentially corrupt) offset.
Found by UBSan's pointer overflow check.
rdar://54843625
Differential Revision: https://reviews.llvm.org/D66979
llvm-svn: 370826
Vedant Kumar