Fix Bug 4657: register scavenger asserts with subreg lowering
When LowerSubregsInstructionPass::LowerInsert eliminates an INSERT_SUBREG
instriction because it is an identity copy, make sure that the same registers
are alive before and after the elimination.
When the super-register is marked <undef> this requires inserting an
IMPLICIT_DEF instruction to make sure the super register is live.
Fix a related bug where a kill flag on the inserted sub-register was not transferred properly.
Finally, clear the undef flag in MachineInstr::addRegisterKilled. Undef implies dead and kill implies live, so they cant both be valid.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@77989 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LowerSubregs.cpp b/lib/CodeGen/LowerSubregs.cpp
index 8572995..dfd666f 100644
--- a/lib/CodeGen/LowerSubregs.cpp
+++ b/lib/CodeGen/LowerSubregs.cpp
@@ -19,6 +19,7 @@
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
@@ -130,6 +131,7 @@
MII != MBB->end(); ++MII)
if (MII->killsRegister(DstReg, &TRI)) {
MII->addRegisterKilled(SuperReg, &TRI, /*AddIfNotFound=*/true);
+ DOUT << "\nsubreg: killed here: " << *MII;
break;
}
} else {
@@ -231,7 +233,7 @@
assert(DstReg == SrcReg && "insert_subreg not a two-address instruction?");
assert(SubIdx != 0 && "Invalid index for insert_subreg");
unsigned DstSubReg = TRI.getSubReg(DstReg, SubIdx);
-
+ assert(DstSubReg && "invalid subregister index for register");
assert(TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
"Insert superreg source must be in a physical register");
assert(TargetRegisterInfo::isPhysicalRegister(InsReg) &&
@@ -240,24 +242,45 @@
DOUT << "subreg: CONVERTING: " << *MI;
if (DstSubReg == InsReg) {
- // No need to insert an identify copy instruction.
- DOUT << "subreg: eliminated!";
+ // No need to insert an identity copy instruction. If the SrcReg was
+ // <undef>, we need to make sure it is alive by inserting an IMPLICIT_DEF
+ if (MI->getOperand(1).isUndef() && !MI->getOperand(0).isDead()) {
+ BuildMI(*MBB, MI, MI->getDebugLoc(),
+ TII.get(TargetInstrInfo::IMPLICIT_DEF), DstReg)
+ .addReg(InsReg, RegState::ImplicitKill);
+ } else {
+ DOUT << "subreg: eliminated!\n";
+ MBB->erase(MI);
+ return true;
+ }
} 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);
+ MachineBasicBlock::iterator CopyMI = MI;
+ --CopyMI;
+
// Transfer the kill/dead flags, if needed.
- if (MI->getOperand(0).isDead())
+ if (MI->getOperand(0).isDead()) {
TransferDeadFlag(MI, DstSubReg, TRI);
- if (MI->getOperand(1).isKill())
+ // Also add a SrcReg<imp-kill> of the super register.
+ CopyMI->addOperand(MachineOperand::CreateReg(DstReg, false, true, true));
+ } else if (MI->getOperand(1).isUndef()) {
+ // If SrcReg was marked <undef> we must make sure it is alive after this
+ // replacement. Add a SrcReg<imp-def> operand.
+ CopyMI->addOperand(MachineOperand::CreateReg(DstReg, true, true));
+ }
+
+ // Make sure the inserted register gets killed
+ if (MI->getOperand(2).isKill())
TransferKillFlag(MI, InsReg, TRI);
+ }
#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
+ MachineBasicBlock::iterator dMI = MI;
+ DOUT << "subreg: " << *(--dMI);
#endif
- }
DOUT << "\n";
MBB->erase(MI);