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Fix Bug 4657: register scavenger asserts with subreg lowering

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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
This commit is contained in:
Jakob Stoklund Olesen
2009-08-03 20:08:18 +00:00
parent ea1c9b7bac
commit 980daea857
3 changed files with 62 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/CodeGen/LowerSubregs.cpp
+31 -8
View File
@@ -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 @@ bool LowerSubregsInstructionPass::LowerExtract(MachineInstr *MI) {
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 @@ bool LowerSubregsInstructionPass::LowerInsert(MachineInstr *MI) {
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 @@ bool LowerSubregsInstructionPass::LowerInsert(MachineInstr *MI) {
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);