[llvm] 2256b35 - Explain the symbols of basic block clusters with an example in the header comments.
Rahman Lavaee via llvm-commits
llvm-commits at lists.llvm.org
Fri Jul 30 12:08:27 PDT 2021
Author: Rahman Lavaee
Date: 2021-07-30T12:08:04-07:00
New Revision: 2256b359d7937b734fd66c9a48b30b10fa441db3
URL: https://github.com/llvm/llvm-project/commit/2256b359d7937b734fd66c9a48b30b10fa441db3
DIFF: https://github.com/llvm/llvm-project/commit/2256b359d7937b734fd66c9a48b30b10fa441db3.diff
LOG: Explain the symbols of basic block clusters with an example in the header comments.
This prevents from confusion with the ``labels`` option.
Reviewed By: snehasish
Differential Revision: https://reviews.llvm.org/D107128
Added:
Modified:
llvm/lib/CodeGen/BasicBlockSections.cpp
Removed:
################################################################################
diff --git a/llvm/lib/CodeGen/BasicBlockSections.cpp b/llvm/lib/CodeGen/BasicBlockSections.cpp
index 1a6eed272ca2..c1901bc46d72 100644
--- a/llvm/lib/CodeGen/BasicBlockSections.cpp
+++ b/llvm/lib/CodeGen/BasicBlockSections.cpp
@@ -21,9 +21,21 @@
// clusters of basic blocks. Every cluster will be emitted into a separate
// section with its basic blocks sequenced in the given order. To get the
// optimized performance, the clusters must form an optimal BB layout for the
-// function. Every cluster's section is labeled with a symbol to allow the
-// linker to reorder the sections in any arbitrary sequence. A global order of
-// these sections would encapsulate the function layout.
+// function. We insert a symbol at the beginning of every cluster's section to
+// allow the linker to reorder the sections in any arbitrary sequence. A global
+// order of these sections would encapsulate the function layout.
+// For example, consider the following clusters for a function foo (consisting
+// of 6 basic blocks 0, 1, ..., 5).
+//
+// 0 2
+// 1 3 5
+//
+// * Basic blocks 0 and 2 are placed in one section with symbol `foo`
+// referencing the beginning of this section.
+// * Basic blocks 1, 3, 5 are placed in a separate section. A new symbol
+// `foo.__part.1` will reference the beginning of this section.
+// * Basic block 4 (note that it is not referenced in the list) is placed in
+// one section, and a new symbol `foo.cold` will point to it.
//
// There are a couple of challenges to be addressed:
//
More information about the llvm-commits
mailing list