//
//===----------------------------------------------------------------------===//
//
-// Simple pass to fills delay slots with NOPs.
+// A pass that attempts to fill instructions with delay slots. If no
+// instructions can be moved into the delay slot then a NOP is placed there.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
using namespace llvm;
STATISTIC(FilledSlots, "Number of delay slots filled");
+namespace llvm {
+cl::opt<bool> DisableDelaySlotFiller(
+ "disable-mblaze-delay-filler",
+ cl::init(false),
+ cl::desc("Disable the MBlaze delay slot filter."),
+ cl::Hidden);
+}
+
namespace {
struct Filler : public MachineFunctionPass {
const TargetInstrInfo *TII;
static char ID;
- Filler(TargetMachine &tm)
+ Filler(TargetMachine &tm)
: MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()) { }
virtual const char *getPassName() const {
char Filler::ID = 0;
} // end of anonymous namespace
+static bool hasImmInstruction(MachineBasicBlock::iterator &candidate) {
+ // Any instruction with an immediate mode operand greater than
+ // 16-bits requires an implicit IMM instruction.
+ unsigned numOper = candidate->getNumOperands();
+ for (unsigned op = 0; op < numOper; ++op) {
+ MachineOperand &mop = candidate->getOperand(op);
+
+ // The operand requires more than 16-bits to represent.
+ if (mop.isImm() && (mop.getImm() < -0x8000 || mop.getImm() > 0x7fff))
+ return true;
+
+ // We must assume that unknown immediate values require more than
+ // 16-bits to represent.
+ if (mop.isGlobal() || mop.isSymbol() || mop.isJTI() || mop.isCPI())
+ return true;
+
+ // FIXME: we could probably check to see if the FP value happens
+ // to not need an IMM instruction. For now we just always
+ // assume that FP values do.
+ if (mop.isFPImm())
+ return true;
+ }
+
+ return false;
+}
+
+static unsigned getLastRealOperand(MachineBasicBlock::iterator &instr) {
+ switch (instr->getOpcode()) {
+ default: return instr->getNumOperands();
+
+ // These instructions have a variable number of operands but the first two
+ // are the "real" operands that we care about during hazard detection.
+ case MBlaze::BRLID:
+ case MBlaze::BRALID:
+ case MBlaze::BRLD:
+ case MBlaze::BRALD:
+ return 2;
+ }
+}
+
+static bool delayHasHazard(MachineBasicBlock::iterator &candidate,
+ MachineBasicBlock::iterator &slot) {
+ // Hazard check
+ MachineBasicBlock::iterator a = candidate;
+ MachineBasicBlock::iterator b = slot;
+ MCInstrDesc desc = candidate->getDesc();
+
+ // MBB layout:-
+ // candidate := a0 = operation(a1, a2)
+ // ...middle bit...
+ // slot := b0 = operation(b1, b2)
+
+ // Possible hazards:-/
+ // 1. a1 or a2 was written during the middle bit
+ // 2. a0 was read or written during the middle bit
+ // 3. a0 is one or more of {b0, b1, b2}
+ // 4. b0 is one or more of {a1, a2}
+ // 5. a accesses memory, and the middle bit
+ // contains a store operation.
+ bool a_is_memory = desc.mayLoad() || desc.mayStore();
+
+ // Determine the number of operands in the slot instruction and in the
+ // candidate instruction.
+ const unsigned aend = getLastRealOperand(a);
+ const unsigned bend = getLastRealOperand(b);
+
+ // Check hazards type 1, 2 and 5 by scanning the middle bit
+ MachineBasicBlock::iterator m = a;
+ for (++m; m != b; ++m) {
+ for (unsigned aop = 0; aop<aend; ++aop) {
+ bool aop_is_reg = a->getOperand(aop).isReg();
+ if (!aop_is_reg) continue;
+
+ bool aop_is_def = a->getOperand(aop).isDef();
+ unsigned aop_reg = a->getOperand(aop).getReg();
+
+ const unsigned mend = getLastRealOperand(m);
+ for (unsigned mop = 0; mop<mend; ++mop) {
+ bool mop_is_reg = m->getOperand(mop).isReg();
+ if (!mop_is_reg) continue;
+
+ bool mop_is_def = m->getOperand(mop).isDef();
+ unsigned mop_reg = m->getOperand(mop).getReg();
+
+ if (aop_is_def && (mop_reg == aop_reg))
+ return true; // Hazard type 2, because aop = a0
+ else if (mop_is_def && (mop_reg == aop_reg))
+ return true; // Hazard type 1, because aop in {a1, a2}
+ }
+ }
+
+ // Check hazard type 5
+ if (a_is_memory && m->getDesc().mayStore())
+ return true;
+ }
+
+ // Check hazard type 3 & 4
+ for (unsigned aop = 0; aop<aend; ++aop) {
+ if (a->getOperand(aop).isReg()) {
+ unsigned aop_reg = a->getOperand(aop).getReg();
+
+ for (unsigned bop = 0; bop<bend; ++bop) {
+ if (b->getOperand(bop).isReg() && !b->getOperand(bop).isImplicit()) {
+ unsigned bop_reg = b->getOperand(bop).getReg();
+ if (aop_reg == bop_reg)
+ return true;
+ }
+ }
+ }
+ }
+
+ return false;
+}
+
+static bool isDelayFiller(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator candidate) {
+ if (candidate == MBB.begin())
+ return false;
+
+ MCInstrDesc brdesc = (--candidate)->getDesc();
+ return (brdesc.hasDelaySlot());
+}
+
+static bool hasUnknownSideEffects(MachineBasicBlock::iterator &I) {
+ if (!I->hasUnmodeledSideEffects())
+ return false;
+
+ unsigned op = I->getOpcode();
+ if (op == MBlaze::ADDK || op == MBlaze::ADDIK ||
+ op == MBlaze::ADDC || op == MBlaze::ADDIC ||
+ op == MBlaze::ADDKC || op == MBlaze::ADDIKC ||
+ op == MBlaze::RSUBK || op == MBlaze::RSUBIK ||
+ op == MBlaze::RSUBC || op == MBlaze::RSUBIC ||
+ op == MBlaze::RSUBKC || op == MBlaze::RSUBIKC)
+ return false;
+
+ return true;
+}
+
+static MachineBasicBlock::iterator
+findDelayInstr(MachineBasicBlock &MBB,MachineBasicBlock::iterator slot) {
+ MachineBasicBlock::iterator I = slot;
+ while (true) {
+ if (I == MBB.begin())
+ break;
+
+ --I;
+ MCInstrDesc desc = I->getDesc();
+ if (desc.hasDelaySlot() || desc.isBranch() || isDelayFiller(MBB,I) ||
+ desc.isCall() || desc.isReturn() || desc.isBarrier() ||
+ hasUnknownSideEffects(I))
+ break;
+
+ if (hasImmInstruction(I) || delayHasHazard(I,slot))
+ continue;
+
+ return I;
+ }
+
+ return MBB.end();
+}
+
/// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
/// Currently, we fill delay slots with NOPs. We assume there is only one
/// delay slot per delayed instruction.
bool Changed = false;
for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I)
if (I->getDesc().hasDelaySlot()) {
+ MachineBasicBlock::iterator D = MBB.end();
MachineBasicBlock::iterator J = I;
- ++J;
- BuildMI(MBB, J, I->getDebugLoc(), TII->get(MBlaze::NOP));
+
+ if (!DisableDelaySlotFiller)
+ D = findDelayInstr(MBB,I);
+
++FilledSlots;
Changed = true;
+
+ if (D == MBB.end())
+ BuildMI(MBB, ++J, I->getDebugLoc(), TII->get(MBlaze::NOP));
+ else
+ MBB.splice(++J, &MBB, D);
}
return Changed;
}
projects / oota-llvm.git / blobdiff