From 6fd78ec8a216f659ce7c0c9912bb81e29595fed9 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 10 Dec 2009 20:59:45 +0000
Subject: It's not safe to coalesce a move where src and dst registers have
 different subregister indices. e.g.: %reg16404:1<def> = MOV8rr
 %reg16412:2<kill>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91061 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SimpleRegisterCoalescing.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

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

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 94f17cec9b..5ebe557d1a 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -1317,7 +1317,13 @@ bool SimpleRegisterCoalescing::JoinCopy(CopyRec &TheCopy, bool &Again) {
                       "coalesced to another register.\n");
       return false;  // Not coalescable.
     }
-  } else if (!tii_->isMoveInstr(*CopyMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)){
+  } else if (tii_->isMoveInstr(*CopyMI, SrcReg, DstReg, SrcSubIdx, DstSubIdx)) {
+    if (SrcSubIdx && DstSubIdx && SrcSubIdx != DstSubIdx) {
+      // e.g. %reg16404:1<def> = MOV8rr %reg16412:2<kill>
+      Again = true;
+      return false;  // Not coalescable.
+    }
+  } else {
     llvm_unreachable("Unrecognized copy instruction!");
   }
 
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