TwoAddressInstructionPass doesn't really know how to merge live intervals when
lowering REG_SEQUENCE instructions.
Insert copies for REG_SEQUENCE sources not killed to avoid breaking later passes.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@104146 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index fdecc5f..21e5a5a 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -1275,9 +1275,10 @@
if (!Seen.insert(SrcReg) ||
MI->getParent() != DefMI->getParent() ||
+ !MI->getOperand(i).isKill() ||
HasOtherRegSequenceUses(SrcReg, MI, MRI)) {
// REG_SEQUENCE cannot have duplicated operands, add a copy.
- // Also add an copy if the source if live-in the block. We don't want
+ // Also add an copy if the source is live-in the block. We don't want
// to end up with a partial-redef of a livein, e.g.
// BB0:
// reg1051:10<def> =
@@ -1287,6 +1288,10 @@
// BB2:
// reg1051:9<def> =
// LiveIntervalAnalysis won't like it.
+ //
+ // If the REG_SEQUENCE doesn't kill its source, keeping live variables
+ // correctly up to date becomes very difficult. Insert a copy.
+ //
const TargetRegisterClass *RC = MRI->getRegClass(SrcReg);
unsigned NewReg = MRI->createVirtualRegister(RC);
MachineBasicBlock::iterator InsertLoc = MI;