From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Fri, 18 Jun 2010 23:10:20 +0000 (+0000)
Subject: Only run CoalesceExtSubRegs when we can expect LiveIntervalAnalysis to clean up
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=fe181f4848a8c774155b8d853c2f53f7e7679872;p=oota-llvm.git

Only run CoalesceExtSubRegs when we can expect LiveIntervalAnalysis to clean up
the inserted INSERT_SUBREGs after us.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106345 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index 048b6698a73..14102d1f3dd 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -1397,8 +1397,11 @@ bool TwoAddressInstructionPass::EliminateRegSequences() {
       MI->eraseFromParent();
     }
 
-    // Try coalescing some EXTRACT_SUBREG instructions.
-    CoalesceExtSubRegs(RealSrcs, DstReg);
+    // Try coalescing some EXTRACT_SUBREG instructions. This can create
+    // INSERT_SUBREG instructions that must have <undef> flags added by
+    // LiveIntervalAnalysis, so only run it when LiveVariables is available.
+    if (LV)
+      CoalesceExtSubRegs(RealSrcs, DstReg);
   }
 
   RegSequences.clear();