From bd0f144cc2549e8c2f853ea0a914abd0aa29444f Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Wed, 24 Sep 2008 23:44:12 +0000
Subject: Give LowerSubregs.cpp a top-level description.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56596 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/LowerSubregs.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'lib/CodeGen/LowerSubregs.cpp')

diff --git a/lib/CodeGen/LowerSubregs.cpp b/lib/CodeGen/LowerSubregs.cpp
index 00038d5c1c..f9cef4ccfb 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"
-- 
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