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llvm-svn: 206996
This commit is contained in:
Diego Novillo 2014-04-23 15:21:21 +00:00
parent 8ebff32487
commit 897c59ce09
1 changed files with 11 additions and 2 deletions
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13
clang/docs/UsersManual.rst
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@ -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 defined. So, if the function has its header at line 280, the offset
13 is at line 293 in the file. 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 b. [OPTIONAL] Discriminator. This is used if the sampled program
was compiled with DWARF discriminator support was compiled with DWARF discriminator support
(http://wiki.dwarfstd.org/index.php?title=Path_Discriminators). (http://wiki.dwarfstd.org/index.php?title=Path_Discriminators).
DWARF discriminators allow the compiler to distinguish between DWARF discriminators are unsigned integer values that allow the
multiple execution paths on the same source line location. 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();``. 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 If the predicate ``cond`` is true 80% of the time, then the edge