Today symbol names generated for machine basic block sections use a
unary encoding to reduce bloat. This is essential when every basic block
in the binary is assigned a symbol however with basic block clusters
(rG05192e585ce175b55f2a26b83b4ed7882785c8e6) when we only need to
generate a few non-temporary symbols we can assign more descriptive
names making them more user friendly. With this change -
Cold cluster section for function foo is named "foo.cold"
Exception cluster section for function foo is named "foo.eh"
Other cluster sections identified by their ids are named "foo.ID"
Using this format works well with existing tools. It will demangle as
expected and works with existing symbolizers, profilers and debuggers
out of the box.
$ c++filt _Z3foov.cold
foo() [clone .cold]
$ c++filt _Z3foov.eh
foo() [clone .eh]
$c++filt _Z3foov.1234
foo() [clone 1234]
Tests for basicblock-sections are updated with some cleanup where
appropriate.
Differential Revision: https://reviews.llvm.org/D79221
Summary:
Instead of adding a ".unlikely" or ".eh" suffix for machine basic blocks,
this change updates the behaviour to use an appropriate prefix
instead. This allows lld to group basic block sections together
when -z,keep-text-section-prefix is specified and matches the behaviour
observed in gcc.
Reviewers: tmsriram, mtrofin, efriedma
Reviewed By: tmsriram, efriedma
Subscribers: eli.friedman, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78742
in the same section.
This allows specifying BasicBlock clusters like the following example:
!foo
!!0 1 2
!!4
This places basic blocks 0, 1, and 2 in one section in this order, and
places basic block #4 in a single section of its own.
This is the second patch in a series of patches to enable basic block
sections support.
This patch adds support for:
* Creating direct jumps at the end of basic blocks that have fall
through instructions.
* New pass, bbsections-prepare, that analyzes placement of basic blocks
in sections.
* Actual placing of a basic block in a unique section with special
handling of exception handling blocks.
* Supports placing a subset of basic blocks in a unique section.
* Support for MIR serialization and deserialization with basic block
sections.
Parent patch : D68063
Differential Revision: https://reviews.llvm.org/D73674
