From 3ef2d60e95f320fe2377d62b1f460cae44f5fdbe Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Tue, 9 Sep 2008 21:44:23 +0000
Subject: [PATCH] Clear preference when it no longer makes sense.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56019 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SimpleRegisterCoalescing.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 6805c8d41c8..5a386dde068 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -1317,6 +1317,14 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
     }
   }
 
+  // If resulting interval has a preference that no longer fits because of subreg
+  // coalescing, just clear the preference.
+  if (ResDstInt->preference && (isExtSubReg || isInsSubReg)) {
+    const TargetRegisterClass *RC = mri_->getRegClass(ResDstInt->reg);
+    if (!RC->contains(ResDstInt->preference))
+      ResDstInt->preference = 0;
+  }
+
   DOUT << "\n\t\tJoined.  Result = "; ResDstInt->print(DOUT, tri_);
   DOUT << "\n";