Fix a register scavenger crash when dealing with undefined subregs.

The LowerSubregs pass needs to preserve implicit def operands attached to
EXTRACT_SUBREG instructions when it replaces those instructions with copies.

llvm-svn: 107189

1 files changed, 18 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LowerSubregs.cpp b/llvm/lib/CodeGen/LowerSubregs.cpp
index 78d8de4b672..2dfd07f7f23 100644
--- a/llvm/lib/CodeGen/LowerSubregs.cpp
+++ b/llvm/lib/CodeGen/LowerSubregs.cpp
@@ -62,6 +62,7 @@ namespace {
     void TransferKillFlag(MachineInstr *MI, unsigned SrcReg,
                           const TargetRegisterInfo *TRI,
                           bool AddIfNotFound = false);
+    void TransferImplicitDefs(MachineInstr *MI);
   };
 
   char LowerSubregsInstructionPass::ID = 0;
@@ -104,6 +105,22 @@ LowerSubregsInstructionPass::TransferKillFlag(MachineInstr *MI,
   }
 }
 
+/// TransferImplicitDefs - MI is a pseudo-instruction, and the lowered
+/// replacement instructions immediately precede it.  Copy any implicit-def
+/// operands from MI to the replacement instruction.
+void
+LowerSubregsInstructionPass::TransferImplicitDefs(MachineInstr *MI) {
+  MachineBasicBlock::iterator CopyMI = MI;
+  --CopyMI;
+
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    MachineOperand &MO = MI->getOperand(i);
+    if (!MO.isReg() || !MO.isImplicit() || MO.isUse())
+      continue;
+    CopyMI->addOperand(MachineOperand::CreateReg(MO.getReg(), true, true));
+  }
+}
+
 bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
   MachineBasicBlock *MBB = MI->getParent();
 
@@ -149,6 +166,7 @@ bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
       TransferDeadFlag(MI, DstReg, TRI);
     if (MI->getOperand(1).isKill())
       TransferKillFlag(MI, SuperReg, TRI, true);
+    TransferImplicitDefs(MI);
     DEBUG({
         MachineBasicBlock::iterator dMI = MI;
         dbgs() << "subreg: " << *(--dMI);