#include "MCTargetDesc/ARMAddressingModes.h"
#include "Thumb2InstrInfo.h"
#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
{ ARM::t2LSLrr, 0, ARM::tLSLrr, 0, 0, 0, 1, 0,0, 1,0,1 },
{ ARM::t2LSRri, ARM::tLSRri, 0, 5, 0, 1, 0, 0,0, 1,0,1 },
{ ARM::t2LSRrr, 0, ARM::tLSRrr, 0, 0, 0, 1, 0,0, 1,0,1 },
- // FIXME: tMOVi8 and tMVN also partially update CPSR but they are less
- // likely to cause issue in the loop. As a size / performance workaround,
- // they are not marked as such.
- { ARM::t2MOVi, ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 0,0,0 },
- { ARM::t2MOVi16,ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 0,1,0 },
+ { ARM::t2MOVi, ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 1,0,0 },
+ { ARM::t2MOVi16,ARM::tMOVi8, 0, 8, 0, 1, 0, 0,0, 1,1,0 },
// FIXME: Do we need the 16-bit 'S' variant?
{ ARM::t2MOVr,ARM::tMOVr, 0, 0, 0, 0, 0, 1,0, 0,0,0 },
{ ARM::t2MUL, 0, ARM::tMUL, 0, 0, 0, 1, 0,0, 1,0,0 },
/// ReduceOpcodeMap - Maps wide opcode to index of entry in ReduceTable.
DenseMap<unsigned, unsigned> ReduceOpcodeMap;
- bool canAddPseudoFlagDep(MachineInstr *Def, MachineInstr *Use,
- bool IsSelfLoop);
+ bool canAddPseudoFlagDep(MachineInstr *Use, bool IsSelfLoop);
bool VerifyPredAndCC(MachineInstr *MI, const ReduceEntry &Entry,
bool is2Addr, ARMCC::CondCodes Pred,
const ReduceEntry &Entry);
bool ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
- const ReduceEntry &Entry, bool LiveCPSR,
- MachineInstr *CPSRDef, bool IsSelfLoop);
+ const ReduceEntry &Entry, bool LiveCPSR, bool IsSelfLoop);
/// ReduceTo2Addr - Reduce a 32-bit instruction to a 16-bit two-address
/// instruction.
bool ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
- const ReduceEntry &Entry,
- bool LiveCPSR, MachineInstr *CPSRDef,
+ const ReduceEntry &Entry, bool LiveCPSR,
bool IsSelfLoop);
/// ReduceToNarrow - Reduce a 32-bit instruction to a 16-bit
/// non-two-address instruction.
bool ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
- const ReduceEntry &Entry,
- bool LiveCPSR, MachineInstr *CPSRDef,
+ const ReduceEntry &Entry, bool LiveCPSR,
bool IsSelfLoop);
/// ReduceMI - Attempt to reduce MI, return true on success.
bool ReduceMI(MachineBasicBlock &MBB, MachineInstr *MI,
- bool LiveCPSR, MachineInstr *CPSRDef,
- bool IsSelfLoop);
+ bool LiveCPSR, bool IsSelfLoop);
/// ReduceMBB - Reduce width of instructions in the specified basic block.
bool ReduceMBB(MachineBasicBlock &MBB);
bool OptimizeSize;
bool MinimizeSize;
+
+ // Last instruction to define CPSR in the current block.
+ MachineInstr *CPSRDef;
+ // Was CPSR last defined by a high latency instruction?
+ // When CPSRDef is null, this refers to CPSR defs in predecessors.
+ bool HighLatencyCPSR;
+
+ struct MBBInfo {
+ // The flags leaving this block have high latency.
+ bool HighLatencyCPSR;
+ // Has this block been visited yet?
+ bool Visited;
+
+ MBBInfo() : HighLatencyCPSR(false), Visited(false) {}
+ };
+
+ SmallVector<MBBInfo, 8> BlockInfo;
};
char Thumb2SizeReduce::ID = 0;
}
return false;
}
+// Check for a likely high-latency flag def.
+static bool isHighLatencyCPSR(MachineInstr *Def) {
+ switch(Def->getOpcode()) {
+ case ARM::FMSTAT:
+ case ARM::tMUL:
+ return true;
+ }
+ return false;
+}
+
/// canAddPseudoFlagDep - For A9 (and other out-of-order) implementations,
/// the 's' 16-bit instruction partially update CPSR. Abort the
/// transformation to avoid adding false dependency on last CPSR setting
/// In this case it would have been ok to narrow the mul.w to muls since there
/// are indirect RAW dependency between the muls and the mul.w
bool
-Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Def, MachineInstr *Use,
- bool FirstInSelfLoop) {
+Thumb2SizeReduce::canAddPseudoFlagDep(MachineInstr *Use, bool FirstInSelfLoop) {
// Disable the check for -Oz (aka OptimizeForSizeHarder).
if (MinimizeSize || !STI->avoidCPSRPartialUpdate())
return false;
- if (!Def)
+ if (!CPSRDef)
// If this BB loops back to itself, conservatively avoid narrowing the
// first instruction that does partial flag update.
- return FirstInSelfLoop;
+ return HighLatencyCPSR || FirstInSelfLoop;
SmallSet<unsigned, 2> Defs;
- for (unsigned i = 0, e = Def->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = Def->getOperand(i);
+ for (unsigned i = 0, e = CPSRDef->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = CPSRDef->getOperand(i);
if (!MO.isReg() || MO.isUndef() || MO.isUse())
continue;
unsigned Reg = MO.getReg();
return false;
}
+ // If the current CPSR has high latency, try to avoid the false dependency.
+ if (HighLatencyCPSR)
+ return true;
+
+ // tMOVi8 usually doesn't start long dependency chains, and there are a lot
+ // of them, so always shrink them when CPSR doesn't have high latency.
+ if (Use->getOpcode() == ARM::t2MOVi ||
+ Use->getOpcode() == ARM::t2MOVi16)
+ return false;
+
// No read-after-write dependency. The narrowing will add false dependency.
return true;
}
bool
Thumb2SizeReduce::ReduceSpecial(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry,
- bool LiveCPSR, MachineInstr *CPSRDef,
- bool IsSelfLoop) {
+ bool LiveCPSR, bool IsSelfLoop) {
unsigned Opc = MI->getOpcode();
if (Opc == ARM::t2ADDri) {
// If the source register is SP, try to reduce to tADDrSPi, otherwise
// it's a normal reduce.
if (MI->getOperand(1).getReg() != ARM::SP) {
- if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop))
+ if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
- return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop);
+ return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
}
// Try to reduce to tADDrSPi.
unsigned Imm = MI->getOperand(2).getImm();
switch (Opc) {
default: break;
case ARM::t2ADDSri: {
- if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop))
+ if (ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
// fallthrough
}
case ARM::t2ADDSrr:
- return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop);
+ return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
}
}
break;
case ARM::t2UXTB:
case ARM::t2UXTH:
if (MI->getOperand(2).getImm() == 0)
- return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop);
+ return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
break;
case ARM::t2MOVi16:
// Can convert only 'pure' immediate operands, not immediates obtained as
// globals' addresses.
if (MI->getOperand(1).isImm())
- return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop);
+ return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
break;
case ARM::t2CMPrr: {
// Try to reduce to the lo-reg only version first. Why there are two
// source insn opcode. So for now, we hack a local entry record to use.
static const ReduceEntry NarrowEntry =
{ ARM::t2CMPrr,ARM::tCMPr, 0, 0, 0, 1, 1,2, 0, 0,1,0 };
- if (ReduceToNarrow(MBB, MI, NarrowEntry, LiveCPSR, CPSRDef, IsSelfLoop))
+ if (ReduceToNarrow(MBB, MI, NarrowEntry, LiveCPSR, IsSelfLoop))
return true;
- return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop);
+ return ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
}
}
return false;
bool
Thumb2SizeReduce::ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry,
- bool LiveCPSR, MachineInstr *CPSRDef,
- bool IsSelfLoop) {
+ bool LiveCPSR, bool IsSelfLoop) {
if (ReduceLimit2Addr != -1 && ((int)Num2Addrs >= ReduceLimit2Addr))
return false;
// Avoid adding a false dependency on partial flag update by some 16-bit
// instructions which has the 's' bit set.
if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
- canAddPseudoFlagDep(CPSRDef, MI, IsSelfLoop))
+ canAddPseudoFlagDep(MI, IsSelfLoop))
return false;
// Add the 16-bit instruction.
bool
Thumb2SizeReduce::ReduceToNarrow(MachineBasicBlock &MBB, MachineInstr *MI,
const ReduceEntry &Entry,
- bool LiveCPSR, MachineInstr *CPSRDef,
- bool IsSelfLoop) {
+ bool LiveCPSR, bool IsSelfLoop) {
if (ReduceLimit != -1 && ((int)NumNarrows >= ReduceLimit))
return false;
// Avoid adding a false dependency on partial flag update by some 16-bit
// instructions which has the 's' bit set.
if (Entry.PartFlag && NewMCID.hasOptionalDef() && HasCC &&
- canAddPseudoFlagDep(CPSRDef, MI, IsSelfLoop))
+ canAddPseudoFlagDep(MI, IsSelfLoop))
return false;
// Add the 16-bit instruction.
}
bool Thumb2SizeReduce::ReduceMI(MachineBasicBlock &MBB, MachineInstr *MI,
- bool LiveCPSR, MachineInstr *CPSRDef,
- bool IsSelfLoop) {
+ bool LiveCPSR, bool IsSelfLoop) {
unsigned Opcode = MI->getOpcode();
DenseMap<unsigned, unsigned>::iterator OPI = ReduceOpcodeMap.find(Opcode);
if (OPI == ReduceOpcodeMap.end())
// Don't attempt normal reductions on "special" cases for now.
if (Entry.Special)
- return ReduceSpecial(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop);
+ return ReduceSpecial(MBB, MI, Entry, LiveCPSR, IsSelfLoop);
// Try to transform to a 16-bit two-address instruction.
if (Entry.NarrowOpc2 &&
- ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop))
+ ReduceTo2Addr(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
// Try to transform to a 16-bit non-two-address instruction.
if (Entry.NarrowOpc1 &&
- ReduceToNarrow(MBB, MI, Entry, LiveCPSR, CPSRDef, IsSelfLoop))
+ ReduceToNarrow(MBB, MI, Entry, LiveCPSR, IsSelfLoop))
return true;
return false;
// Yes, CPSR could be livein.
bool LiveCPSR = MBB.isLiveIn(ARM::CPSR);
- MachineInstr *CPSRDef = 0;
MachineInstr *BundleMI = 0;
+ CPSRDef = 0;
+ HighLatencyCPSR = false;
+
+ // Check predecessors for the latest CPSRDef.
+ bool HasBackEdges = false;
+ for (MachineBasicBlock::pred_iterator
+ I = MBB.pred_begin(), E = MBB.pred_end(); I != E; ++I) {
+ const MBBInfo &PInfo = BlockInfo[(*I)->getNumber()];
+ if (!PInfo.Visited) {
+ // Since blocks are visited in RPO, this must be a back-edge.
+ HasBackEdges = true;
+ continue;
+ }
+ if (PInfo.HighLatencyCPSR) {
+ HighLatencyCPSR = true;
+ break;
+ }
+ }
+
// If this BB loops back to itself, conservatively avoid narrowing the
// first instruction that does partial flag update.
bool IsSelfLoop = MBB.isSuccessor(&MBB);
BundleMI = MI;
continue;
}
+ if (MI->isDebugValue())
+ continue;
LiveCPSR = UpdateCPSRUse(*MI, LiveCPSR);
// Does NextMII belong to the same bundle as MI?
bool NextInSameBundle = NextMII != E && NextMII->isBundledWithPred();
- if (ReduceMI(MBB, MI, LiveCPSR, CPSRDef, IsSelfLoop)) {
+ if (ReduceMI(MBB, MI, LiveCPSR, IsSelfLoop)) {
Modified = true;
MachineBasicBlock::instr_iterator I = prior(NextMII);
MI = &*I;
if (MI->isCall()) {
// Calls don't really set CPSR.
CPSRDef = 0;
+ HighLatencyCPSR = false;
IsSelfLoop = false;
} else if (DefCPSR) {
// This is the last CPSR defining instruction.
CPSRDef = MI;
+ HighLatencyCPSR = isHighLatencyCPSR(CPSRDef);
IsSelfLoop = false;
}
}
+ MBBInfo &Info = BlockInfo[MBB.getNumber()];
+ Info.HighLatencyCPSR = HighLatencyCPSR;
+ Info.Visited = true;
return Modified;
}
MinimizeSize = FnAttrs.hasAttribute(AttributeSet::FunctionIndex,
Attribute::MinSize);
+ BlockInfo.clear();
+ BlockInfo.resize(MF.getNumBlockIDs());
+
+ // Visit blocks in reverse post-order so LastCPSRDef is known for all
+ // predecessors.
+ ReversePostOrderTraversal<MachineFunction*> RPOT(&MF);
bool Modified = false;
- for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
- Modified |= ReduceMBB(*I);
+ for (ReversePostOrderTraversal<MachineFunction*>::rpo_iterator
+ I = RPOT.begin(), E = RPOT.end(); I != E; ++I)
+ Modified |= ReduceMBB(**I);
return Modified;
}
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