It's not safe to remove SUBREG_TO_REG that looks like identity copies, e.g. movl %eax, %eax on x86-64 actually does a zero-extend.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52421 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LowerSubregs.cpp b/lib/CodeGen/LowerSubregs.cpp
index 296e6d4..e2e68d8 100644
--- a/lib/CodeGen/LowerSubregs.cpp
+++ b/lib/CodeGen/LowerSubregs.cpp
@@ -108,20 +108,15 @@
DOUT << "subreg: CONVERTING: " << *MI;
- if (DstSubReg == InsReg) {
- // No need to insert an identify copy instruction.
- DOUT << "subreg: eliminated!";
- } else {
- // Insert sub-register copy
- const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
- const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
- TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
+ // Insert sub-register copy
+ const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
+ const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
+ TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
+ MachineBasicBlock::iterator dMI = MI;
+ DOUT << "subreg: " << *(--dMI);
#endif
- }
DOUT << "\n";
MBB->remove(MI);