From: Dan Gohman <gohman@apple.com>
Date: Wed, 24 Sep 2008 23:44:12 +0000 (+0000)
Subject: Give LowerSubregs.cpp a top-level description.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=bd0f144cc2549e8c2f853ea0a914abd0aa29444f;p=oota-llvm.git

Give LowerSubregs.cpp a top-level description.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56596 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/LowerSubregs.cpp b/lib/CodeGen/LowerSubregs.cpp
index 00038d5c1c7..f9cef4ccfb7 100644
--- a/lib/CodeGen/LowerSubregs.cpp
+++ b/lib/CodeGen/LowerSubregs.cpp
@@ -6,6 +6,13 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// This file defines a MachineFunction pass which runs after register
+// allocation that turns subreg insert/extract instructions into register
+// copies, as needed. This ensures correct codegen even if the coalescer
+// isn't able to remove all subreg instructions.
+//
+//===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "lowersubregs"
 #include "llvm/CodeGen/Passes.h"