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| author | Diego Novillo <dnovillo@google.com> | 2014-04-23 15:21:21 +0000 |
|---|---|---|
| committer | Diego Novillo <dnovillo@google.com> | 2014-04-23 15:21:21 +0000 |
| commit | ebb76662bed11638e10fed222d512cbc40e17db4 (patch) | |
| tree | db2ef1802e173f88efd57e8602279d33bc627fb3 /docs/UsersManual.rst | |
| parent | d6d7a5d1f65b1fecbd86e283aae907a2a41bcefb (diff) | |
| download | clang-ebb76662bed11638e10fed222d512cbc40e17db4.tar.gz clang-ebb76662bed11638e10fed222d512cbc40e17db4.tar.bz2 clang-ebb76662bed11638e10fed222d512cbc40e17db4.tar.xz | |
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git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206996 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/UsersManual.rst')
| -rw-r--r-- | docs/UsersManual.rst | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/docs/UsersManual.rst b/docs/UsersManual.rst index 2ea0f7b577..acf576317c 100644 --- a/docs/UsersManual.rst +++ b/docs/UsersManual.rst @@ -1180,11 +1180,20 @@ a. Source line offset. This number represents the line number defined. So, if the function has its header at line 280, the offset 13 is at line 293 in the file. + Note that this offset should never be a negative number. This could + happen in cases like macros. The debug machinery will register the + line number at the point of macro expansion. So, if the macro was + expanded in a line before the start of the function, the profile + converter should emit a 0 as the offset (this means that the optimizers + will not be able to associate a meaningful weight to the instructions + in the macro). + b. [OPTIONAL] Discriminator. This is used if the sampled program was compiled with DWARF discriminator support (http://wiki.dwarfstd.org/index.php?title=Path_Discriminators). - DWARF discriminators allow the compiler to distinguish between - multiple execution paths on the same source line location. + DWARF discriminators are unsigned integer values that allow the + compiler to distinguish between multiple execution paths on the + same source line location. For example, consider the line of code ``if (cond) foo(); else bar();``. If the predicate ``cond`` is true 80% of the time, then the edge |