//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "regalloc"
#include "llvm/CodeGen/VirtRegMap.h"
#include "LiveDebugVariables.h"
#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SparseSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
#include <algorithm>
using namespace llvm;
+#define DEBUG_TYPE "regalloc"
+
STATISTIC(NumSpillSlots, "Number of spill slots allocated");
STATISTIC(NumIdCopies, "Number of identity moves eliminated after rewriting");
bool VirtRegMap::runOnMachineFunction(MachineFunction &mf) {
MRI = &mf.getRegInfo();
- TII = mf.getTarget().getInstrInfo();
- TRI = mf.getTarget().getRegisterInfo();
+ TII = mf.getSubtarget().getInstrInfo();
+ TRI = mf.getSubtarget().getRegisterInfo();
MF = &mf;
Virt2PhysMap.clear();
SlotIndexes *Indexes;
LiveIntervals *LIS;
VirtRegMap *VRM;
+ SparseSet<unsigned> PhysRegs;
void rewrite();
void addMBBLiveIns();
static char ID;
VirtRegRewriter() : MachineFunctionPass(ID) {}
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ void getAnalysisUsage(AnalysisUsage &AU) const override;
- virtual bool runOnMachineFunction(MachineFunction&);
+ bool runOnMachineFunction(MachineFunction&) override;
};
} // end anonymous namespace
bool VirtRegRewriter::runOnMachineFunction(MachineFunction &fn) {
MF = &fn;
TM = &MF->getTarget();
- TRI = TM->getRegisterInfo();
- TII = TM->getInstrInfo();
+ TRI = MF->getSubtarget().getRegisterInfo();
+ TII = MF->getSubtarget().getInstrInfo();
MRI = &MF->getRegInfo();
Indexes = &getAnalysis<SlotIndexes>();
LIS = &getAnalysis<LiveIntervals>();
SmallVector<unsigned, 8> SuperKills;
SmallPtrSet<const MachineInstr *, 4> NoReturnInsts;
+ // Here we have a SparseSet to hold which PhysRegs are actually encountered
+ // in the MF we are about to iterate over so that later when we call
+ // setPhysRegUsed, we are only doing it for physRegs that were actually found
+ // in the program and not for all of the possible physRegs for the given
+ // target architecture. If the target has a lot of physRegs, then for a small
+ // program there will be a significant compile time reduction here.
+ PhysRegs.clear();
+ PhysRegs.setUniverse(TRI->getNumRegs());
+
+ // The function with uwtable should guarantee that the stack unwinder
+ // can unwind the stack to the previous frame. Thus, we can't apply the
+ // noreturn optimization if the caller function has uwtable attribute.
+ bool HasUWTable = MF->getFunction()->hasFnAttribute(Attribute::UWTable);
+
for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
MBBI != MBBE; ++MBBI) {
DEBUG(MBBI->print(dbgs(), Indexes));
MachineInstr *MI = MII;
++MII;
- // Check if this instruction is a call to a noreturn function.
- // If so, all the definitions set by this instruction can be ignored.
- if (IsExitBB && MI->isCall())
+ // Check if this instruction is a call to a noreturn function. If this
+ // is a call to noreturn function and we don't need the stack unwinding
+ // functionality (i.e. this function does not have uwtable attribute and
+ // the callee function has the nounwind attribute), then we can ignore
+ // the definitions set by this instruction.
+ if (!HasUWTable && IsExitBB && MI->isCall()) {
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
MachineOperand &MO = *MOI;
if (!MO.isGlobal())
continue;
const Function *Func = dyn_cast<Function>(MO.getGlobal());
- if (!Func || !Func->hasFnAttribute(Attribute::NoReturn))
+ if (!Func || !Func->hasFnAttribute(Attribute::NoReturn) ||
+ // We need to keep correct unwind information
+ // even if the function will not return, since the
+ // runtime may need it.
+ !Func->hasFnAttribute(Attribute::NoUnwind))
continue;
NoReturnInsts.insert(MI);
break;
}
+ }
for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
MOE = MI->operands_end(); MOI != MOE; ++MOI) {
if (MO.isRegMask())
MRI->addPhysRegsUsedFromRegMask(MO.getRegMask());
+ // If we encounter a VirtReg or PhysReg then get at the PhysReg and add
+ // it to the physreg bitset. Later we use only the PhysRegs that were
+ // actually encountered in the MF to populate the MRI's used physregs.
+ if (MO.isReg() && MO.getReg())
+ PhysRegs.insert(
+ TargetRegisterInfo::isVirtualRegister(MO.getReg()) ?
+ VRM->getPhys(MO.getReg()) :
+ MO.getReg());
+
if (!MO.isReg() || !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
continue;
unsigned VirtReg = MO.getReg();
// Tell MRI about physical registers in use.
if (NoReturnInsts.empty()) {
- for (unsigned Reg = 1, RegE = TRI->getNumRegs(); Reg != RegE; ++Reg)
- if (!MRI->reg_nodbg_empty(Reg))
- MRI->setPhysRegUsed(Reg);
+ for (SparseSet<unsigned>::iterator
+ RegI = PhysRegs.begin(), E = PhysRegs.end(); RegI != E; ++RegI)
+ if (!MRI->reg_nodbg_empty(*RegI))
+ MRI->setPhysRegUsed(*RegI);
} else {
- for (unsigned Reg = 1, RegE = TRI->getNumRegs(); Reg != RegE; ++Reg) {
+ for (SparseSet<unsigned>::iterator
+ I = PhysRegs.begin(), E = PhysRegs.end(); I != E; ++I) {
+ unsigned Reg = *I;
if (MRI->reg_nodbg_empty(Reg))
continue;
// Check if this register has a use that will impact the rest of the
// code. Uses in debug and noreturn instructions do not impact the
// generated code.
- for (MachineRegisterInfo::reg_nodbg_iterator It =
- MRI->reg_nodbg_begin(Reg),
- EndIt = MRI->reg_nodbg_end(); It != EndIt; ++It) {
- if (!NoReturnInsts.count(&(*It))) {
+ for (MachineInstr &It : MRI->reg_nodbg_instructions(Reg)) {
+ if (!NoReturnInsts.count(&It)) {
MRI->setPhysRegUsed(Reg);
break;
}
}
}
}
+
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