[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

8 files changed, 23 insertions, 9 deletions

diff --git a/llvm/test/tools/llvm-profdata/Inputs/c-general.profraw b/llvm/test/tools/llvm-profdata/Inputs/c-general.profraw
index 332d11b140f..c453d806770 100644
--- a/llvm/test/tools/llvm-profdata/Inputs/c-general.profraw
+++ b/llvm/test/tools/llvm-profdata/Inputs/c-general.profraw
diff --git a/llvm/test/tools/llvm-profdata/c-general.test b/llvm/test/tools/llvm-profdata/c-general.test
index ed4e61962e4..d4ed384ad60 100644
--- a/llvm/test/tools/llvm-profdata/c-general.test
+++ b/llvm/test/tools/llvm-profdata/c-general.test
@@ -5,7 +5,7 @@ $ SRC=path/to/llvm
 $ CFE=$SRC/tools/clang
 $ TESTDIR=$SRC/test/tools/llvm-profdata
 $ CFE_TESTDIR=$CFE/test/Profile
-$ clang -o a.out -fprofile-instr-generate $CFE_TESTDIR/c-general.c
+$ clang -o a.out -fprofile-instr-generate $CFE_TESTDIR/c-general.c -mllvm -enable-name-compression=false
 $ LLVM_PROFILE_FILE=$TESTDIR/Inputs/c-general.profraw ./a.out
 
 RUN: llvm-profdata show %p/Inputs/c-general.profraw -o - | FileCheck %s
@@ -14,7 +14,7 @@ RUN: llvm-profdata show %p/Inputs/c-general.profraw -o - --function=switches | F
 
 SWITCHES-LABEL: Counters:
 SWITCHES-NEXT:   switches:
-SWITCHES-NEXT:     Hash: 0x2618e4f23f2e8daa
+SWITCHES-NEXT:     Hash: 0xa50a07f391ae4be5
 SWITCHES-NEXT:     Counters: 19
 SWITCHES-NEXT:     Function count: 1
 SWITCHES-LABEL: Functions shown: 1
diff --git a/llvm/test/tools/llvm-profdata/malformed-ptr-to-counter-array.test b/llvm/test/tools/llvm-profdata/malformed-ptr-to-counter-array.test
index c355bdcbdea..bad4eb30182 100644
--- a/llvm/test/tools/llvm-profdata/malformed-ptr-to-counter-array.test
+++ b/llvm/test/tools/llvm-profdata/malformed-ptr-to-counter-array.test
@@ -10,9 +10,11 @@
 // INSTR_PROF_RAW_HEADER(uint64_t, ValueKindLast, IPVK_Last)
 
 RUN: printf '\201rforpl\377' > %t.profraw
-RUN: printf '\4\0\0\0\0\0\0\0' >> %t.profraw
+RUN: printf '\5\0\0\0\0\0\0\0' >> %t.profraw
 RUN: printf '\1\0\0\0\0\0\0\0' >> %t.profraw
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t.profraw
 RUN: printf '\2\0\0\0\0\0\0\0' >> %t.profraw
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t.profraw
 RUN: printf '\10\0\0\0\0\0\0\0' >> %t.profraw
 RUN: printf '\0\0\6\0\1\0\0\0' >> %t.profraw
 RUN: printf '\0\0\6\0\2\0\0\0' >> %t.profraw
diff --git a/llvm/test/tools/llvm-profdata/raw-32-bits-be.test b/llvm/test/tools/llvm-profdata/raw-32-bits-be.test
index d6e1daa1655..cebd25a07f4 100644
--- a/llvm/test/tools/llvm-profdata/raw-32-bits-be.test
+++ b/llvm/test/tools/llvm-profdata/raw-32-bits-be.test
@@ -1,7 +1,9 @@
 RUN: printf '\377lprofR\201' > %t
-RUN: printf '\0\0\0\0\0\0\0\4' >> %t
+RUN: printf '\0\0\0\0\0\0\0\5' >> %t
 RUN: printf '\0\0\0\0\0\0\0\2' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\0\0\0\0\0\0\0\3' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\0\0\0\0\0\0\0\20' >> %t
 RUN: printf '\0\0\0\0\1\0\0\0' >> %t
 RUN: printf '\0\0\0\0\2\0\0\0' >> %t
diff --git a/llvm/test/tools/llvm-profdata/raw-32-bits-le.test b/llvm/test/tools/llvm-profdata/raw-32-bits-le.test
index cd36aafc9ad..a176f80ec95 100644
--- a/llvm/test/tools/llvm-profdata/raw-32-bits-le.test
+++ b/llvm/test/tools/llvm-profdata/raw-32-bits-le.test
@@ -1,7 +1,9 @@
 RUN: printf '\201Rforpl\377' > %t
-RUN: printf '\4\0\0\0\0\0\0\0' >> %t
+RUN: printf '\5\0\0\0\0\0\0\0' >> %t
 RUN: printf '\2\0\0\0\0\0\0\0' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\3\0\0\0\0\0\0\0' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\20\0\0\0\0\0\0\0' >> %t
 RUN: printf '\0\0\0\1\0\0\0\0' >> %t
 RUN: printf '\0\0\0\2\0\0\0\0' >> %t
diff --git a/llvm/test/tools/llvm-profdata/raw-64-bits-be.test b/llvm/test/tools/llvm-profdata/raw-64-bits-be.test
index 75cc84d6886..c679207102e 100644
--- a/llvm/test/tools/llvm-profdata/raw-64-bits-be.test
+++ b/llvm/test/tools/llvm-profdata/raw-64-bits-be.test
@@ -1,7 +1,9 @@
 RUN: printf '\377lprofr\201' > %t
-RUN: printf '\0\0\0\0\0\0\0\4' >> %t
+RUN: printf '\0\0\0\0\0\0\0\5' >> %t
 RUN: printf '\0\0\0\0\0\0\0\2' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\0\0\0\0\0\0\0\3' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\0\0\0\0\0\0\0\20' >> %t
 RUN: printf '\0\0\0\1\0\4\0\0' >> %t
 RUN: printf '\0\0\0\2\0\4\0\0' >> %t
diff --git a/llvm/test/tools/llvm-profdata/raw-64-bits-le.test b/llvm/test/tools/llvm-profdata/raw-64-bits-le.test
index d8a9c9a7586..8e179a87162 100644
--- a/llvm/test/tools/llvm-profdata/raw-64-bits-le.test
+++ b/llvm/test/tools/llvm-profdata/raw-64-bits-le.test
@@ -1,7 +1,9 @@
 RUN: printf '\201rforpl\377' > %t
-RUN: printf '\4\0\0\0\0\0\0\0' >> %t
+RUN: printf '\5\0\0\0\0\0\0\0' >> %t
 RUN: printf '\2\0\0\0\0\0\0\0' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\3\0\0\0\0\0\0\0' >> %t
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t
 RUN: printf '\20\0\0\0\0\0\0\0' >> %t
 RUN: printf '\0\0\4\0\1\0\0\0' >> %t
 RUN: printf '\0\0\4\0\2\0\0\0' >> %t
diff --git a/llvm/test/tools/llvm-profdata/raw-two-profiles.test b/llvm/test/tools/llvm-profdata/raw-two-profiles.test
index a377375c176..9cd8a8c7b00 100644
--- a/llvm/test/tools/llvm-profdata/raw-two-profiles.test
+++ b/llvm/test/tools/llvm-profdata/raw-two-profiles.test
@@ -1,7 +1,9 @@
 RUN: printf '\201rforpl\377' > %t-foo.profraw
-RUN: printf '\4\0\0\0\0\0\0\0' >> %t-foo.profraw
+RUN: printf '\5\0\0\0\0\0\0\0' >> %t-foo.profraw
 RUN: printf '\1\0\0\0\0\0\0\0' >> %t-foo.profraw
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t-foo.profraw
 RUN: printf '\1\0\0\0\0\0\0\0' >> %t-foo.profraw
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t-foo.profraw
 RUN: printf '\10\0\0\0\0\0\0\0' >> %t-foo.profraw
 RUN: printf '\0\0\4\0\1\0\0\0' >> %t-foo.profraw
 RUN: printf '\0\0\4\0\2\0\0\0' >> %t-foo.profraw
@@ -18,9 +20,11 @@ RUN: printf '\023\0\0\0\0\0\0\0' >> %t-foo.profraw
 RUN: printf '\3\0foo\0\0\0' >> %t-foo.profraw
 
 RUN: printf '\201rforpl\377' > %t-bar.profraw
-RUN: printf '\4\0\0\0\0\0\0\0' >> %t-bar.profraw
+RUN: printf '\5\0\0\0\0\0\0\0' >> %t-bar.profraw
 RUN: printf '\1\0\0\0\0\0\0\0' >> %t-bar.profraw
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t-bar.profraw
 RUN: printf '\2\0\0\0\0\0\0\0' >> %t-bar.profraw
+RUN: printf '\0\0\0\0\0\0\0\0' >> %t-bar.profraw
 RUN: printf '\10\0\0\0\0\0\0\0' >> %t-bar.profraw
 RUN: printf '\0\0\6\0\1\0\0\0' >> %t-bar.profraw
 RUN: printf '\0\0\6\0\2\0\0\0' >> %t-bar.profraw