[llvm-commits] [llvm] r61075 - in /llvm/trunk: include/llvm/CodeGen/ScheduleDAG.h include/llvm/Target/TargetSubtarget.h lib/CodeGen/LatencyPriorityQueue.cpp lib/CodeGen/ScheduleDAGInstrs.cpp lib/Target/X86/X86Subtarget.cpp lib/Target/X86/X86Subtarget.h
Dan Gohman
gohman at apple.com
Mon Dec 15 19:35:02 PST 2008
Author: djg
Date: Mon Dec 15 21:35:01 2008
New Revision: 61075
URL: http://llvm.org/viewvc/llvm-project?rev=61075&view=rev
Log:
Add initial support for back-scheduling address computations,
especially in the case of addresses computed from loop induction
variables.
Modified:
llvm/trunk/include/llvm/CodeGen/ScheduleDAG.h
llvm/trunk/include/llvm/Target/TargetSubtarget.h
llvm/trunk/lib/CodeGen/LatencyPriorityQueue.cpp
llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp
llvm/trunk/lib/Target/X86/X86Subtarget.cpp
llvm/trunk/lib/Target/X86/X86Subtarget.h
Modified: llvm/trunk/include/llvm/CodeGen/ScheduleDAG.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/ScheduleDAG.h?rev=61075&r1=61074&r2=61075&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/ScheduleDAG.h (original)
+++ llvm/trunk/include/llvm/CodeGen/ScheduleDAG.h Mon Dec 15 21:35:01 2008
@@ -242,6 +242,7 @@
bool isPending : 1; // True once pending.
bool isAvailable : 1; // True once available.
bool isScheduled : 1; // True once scheduled.
+ bool isScheduleHigh : 1; // True if preferable to schedule high.
private:
bool isDepthCurrent : 1; // True if Depth is current.
bool isHeightCurrent : 1; // True if Height is current.
@@ -258,7 +259,7 @@
Latency(0), NumPreds(0), NumSuccs(0), NumPredsLeft(0), NumSuccsLeft(0),
isTwoAddress(false), isCommutable(false), hasPhysRegDefs(false),
isPending(false), isAvailable(false), isScheduled(false),
- isDepthCurrent(false), isHeightCurrent(false),
+ isScheduleHigh(false), isDepthCurrent(false), isHeightCurrent(false),
Depth(0), Height(0),
CopyDstRC(NULL), CopySrcRC(NULL) {}
@@ -269,7 +270,7 @@
Latency(0), NumPreds(0), NumSuccs(0), NumPredsLeft(0), NumSuccsLeft(0),
isTwoAddress(false), isCommutable(false), hasPhysRegDefs(false),
isPending(false), isAvailable(false), isScheduled(false),
- isDepthCurrent(false), isHeightCurrent(false),
+ isScheduleHigh(false), isDepthCurrent(false), isHeightCurrent(false),
Depth(0), Height(0),
CopyDstRC(NULL), CopySrcRC(NULL) {}
Modified: llvm/trunk/include/llvm/Target/TargetSubtarget.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Target/TargetSubtarget.h?rev=61075&r1=61074&r2=61075&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Target/TargetSubtarget.h (original)
+++ llvm/trunk/include/llvm/Target/TargetSubtarget.h Mon Dec 15 21:35:01 2008
@@ -29,6 +29,12 @@
TargetSubtarget();
public:
virtual ~TargetSubtarget();
+
+ /// getSpecialAddressLatency - For targets where it is beneficial to
+ /// backschedule instructions that compute addresses, return a value
+ /// indicating the number of scheduling cycles of backscheduling that
+ /// should be attempted.
+ virtual unsigned getSpecialAddressLatency() const { return 0; }
};
} // End llvm namespace
Modified: llvm/trunk/lib/CodeGen/LatencyPriorityQueue.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LatencyPriorityQueue.cpp?rev=61075&r1=61074&r2=61075&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/LatencyPriorityQueue.cpp (original)
+++ llvm/trunk/lib/CodeGen/LatencyPriorityQueue.cpp Mon Dec 15 21:35:01 2008
@@ -19,6 +19,14 @@
using namespace llvm;
bool latency_sort::operator()(const SUnit *LHS, const SUnit *RHS) const {
+ // The isScheduleHigh flag allows nodes with wraparound dependencies that
+ // cannot easily be modeled as edges with latencies to be scheduled as
+ // soon as possible in a top-down schedule.
+ if (LHS->isScheduleHigh && !RHS->isScheduleHigh)
+ return false;
+ if (!LHS->isScheduleHigh && RHS->isScheduleHigh)
+ return true;
+
unsigned LHSNum = LHS->NodeNum;
unsigned RHSNum = RHS->NodeNum;
Modified: llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp?rev=61075&r1=61074&r2=61075&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp (original)
+++ llvm/trunk/lib/CodeGen/ScheduleDAGInstrs.cpp Mon Dec 15 21:35:01 2008
@@ -15,6 +15,7 @@
#define DEBUG_TYPE "sched-instrs"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
#include "llvm/CodeGen/PseudoSourceValue.h"
@@ -29,6 +30,59 @@
#include <map>
using namespace llvm;
+namespace {
+ class VISIBILITY_HIDDEN LoopDependencies {
+ const MachineLoopInfo &MLI;
+ const MachineDominatorTree &MDT;
+
+ public:
+ typedef std::map<unsigned, std::pair<const MachineOperand *, unsigned> >
+ LoopDeps;
+ LoopDeps Deps;
+
+ LoopDependencies(const MachineLoopInfo &mli,
+ const MachineDominatorTree &mdt) :
+ MLI(mli), MDT(mdt) {}
+
+ void VisitLoop(const MachineLoop *Loop) {
+ Deps.clear();
+ MachineBasicBlock *Header = Loop->getHeader();
+ SmallSet<unsigned, 8> LoopLiveIns;
+ for (MachineBasicBlock::livein_iterator LI = Header->livein_begin(),
+ LE = Header->livein_end(); LI != LE; ++LI)
+ LoopLiveIns.insert(*LI);
+
+ VisitRegion(MDT.getNode(Header), Loop, LoopLiveIns);
+ }
+
+ private:
+ void VisitRegion(const MachineDomTreeNode *Node,
+ const MachineLoop *Loop,
+ const SmallSet<unsigned, 8> &LoopLiveIns) {
+ MachineBasicBlock *MBB = Node->getBlock();
+ if (!Loop->contains(MBB)) return;
+
+ unsigned Count = 0;
+ for (MachineBasicBlock::const_iterator I = MBB->begin(), E = MBB->end();
+ I != E; ++I, ++Count) {
+ const MachineInstr *MI = I;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.isUse())
+ continue;
+ unsigned MOReg = MO.getReg();
+ if (LoopLiveIns.count(MOReg))
+ Deps.insert(std::make_pair(MOReg, std::make_pair(&MO, Count)));
+ }
+ }
+
+ const std::vector<MachineDomTreeNode*> &Children = Node->getChildren();
+ for (unsigned I = 0, E = Children.size(); I != E; ++I)
+ VisitRegion(Children[I], Loop, LoopLiveIns);
+ }
+ };
+}
+
ScheduleDAGInstrs::ScheduleDAGInstrs(MachineBasicBlock *bb,
const TargetMachine &tm,
const MachineLoopInfo &mli,
@@ -65,9 +119,27 @@
// all the work of the block is done before the terminator.
SUnit *Terminator = 0;
+ LoopDependencies LoopRegs(MLI, MDT);
+
+ // Track which regs are live into a loop, to help guide back-edge-aware
+ // scheduling.
+ SmallSet<unsigned, 8> LoopLiveInRegs;
+ if (MachineLoop *ML = MLI.getLoopFor(BB))
+ if (BB == ML->getLoopLatch()) {
+ MachineBasicBlock *Header = ML->getHeader();
+ for (MachineBasicBlock::livein_iterator I = Header->livein_begin(),
+ E = Header->livein_end(); I != E; ++I)
+ LoopLiveInRegs.insert(*I);
+ LoopRegs.VisitLoop(ML);
+ }
+
// Check to see if the scheduler cares about latencies.
bool UnitLatencies = ForceUnitLatencies();
+ // Ask the target if address-backscheduling is desirable, and if so how much.
+ unsigned SpecialAddressLatency =
+ TM.getSubtarget<TargetSubtarget>().getSpecialAddressLatency();
+
for (MachineBasicBlock::iterator MII = BB->end(), MIE = BB->begin();
MII != MIE; --MII) {
MachineInstr *MI = prior(MII);
@@ -118,7 +190,21 @@
for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
SUnit *UseSU = UseList[i];
if (UseSU != SU) {
- UseSU->addPred(SDep(SU, SDep::Data, DataLatency, Reg));
+ unsigned LDataLatency = DataLatency;
+ // Optionally add in a special extra latency for nodes that
+ // feed addresses.
+ // TODO: Do this for register aliases too.
+ if (SpecialAddressLatency != 0 && !UnitLatencies) {
+ MachineInstr *UseMI = UseSU->getInstr();
+ const TargetInstrDesc &UseTID = UseMI->getDesc();
+ int RegUseIndex = UseMI->findRegisterUseOperandIdx(Reg);
+ assert(RegUseIndex >= 0 && "UseMI doesn's use register!");
+ if ((UseTID.mayLoad() || UseTID.mayStore()) &&
+ (unsigned)RegUseIndex < UseTID.getNumOperands() &&
+ UseTID.OpInfo[RegUseIndex].isLookupPtrRegClass())
+ LDataLatency += SpecialAddressLatency;
+ }
+ UseSU->addPred(SDep(SU, SDep::Data, LDataLatency, Reg));
}
}
for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
@@ -130,6 +216,51 @@
}
}
+ // If a def is going to wrap back around to the top of the loop,
+ // backschedule it.
+ // TODO: Blocks in loops without terminators can benefit too.
+ if (!UnitLatencies && Terminator && DefList.empty()) {
+ LoopDependencies::LoopDeps::iterator I = LoopRegs.Deps.find(Reg);
+ if (I != LoopRegs.Deps.end()) {
+ const MachineOperand *UseMO = I->second.first;
+ unsigned Count = I->second.second;
+ const MachineInstr *UseMI = UseMO->getParent();
+ unsigned UseMOIdx = UseMO - &UseMI->getOperand(0);
+ const TargetInstrDesc &UseTID = UseMI->getDesc();
+ // TODO: If we knew the total depth of the region here, we could
+ // handle the case where the whole loop is inside the region but
+ // is large enough that the isScheduleHigh trick isn't needed.
+ if (UseMOIdx < UseTID.getNumOperands()) {
+ // Currently, we only support scheduling regions consisting of
+ // single basic blocks. Check to see if the instruction is in
+ // the same region by checking to see if it has the same parent.
+ if (UseMI->getParent() != MI->getParent()) {
+ unsigned Latency = SU->Latency;
+ if (UseTID.OpInfo[UseMOIdx].isLookupPtrRegClass())
+ Latency += SpecialAddressLatency;
+ // This is a wild guess as to the portion of the latency which
+ // will be overlapped by work done outside the current
+ // scheduling region.
+ Latency -= std::min(Latency, Count);
+ // Add the artifical edge.
+ Terminator->addPred(SDep(SU, SDep::Order, Latency,
+ /*Reg=*/0, /*isNormalMemory=*/false,
+ /*isMustAlias=*/false,
+ /*isArtificial=*/true));
+ } else if (SpecialAddressLatency > 0 &&
+ UseTID.OpInfo[UseMOIdx].isLookupPtrRegClass()) {
+ // The entire loop body is within the current scheduling region
+ // and the latency of this operation is assumed to be greater
+ // than the latency of the loop.
+ // TODO: Recursively mark data-edge predecessors as
+ // isScheduleHigh too.
+ SU->isScheduleHigh = true;
+ }
+ }
+ LoopRegs.Deps.erase(I);
+ }
+ }
+
UseList.clear();
if (!MO.isDead())
DefList.clear();
Modified: llvm/trunk/lib/Target/X86/X86Subtarget.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86Subtarget.cpp?rev=61075&r1=61074&r2=61075&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86Subtarget.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86Subtarget.cpp Mon Dec 15 21:35:01 2008
@@ -93,6 +93,17 @@
return 0;
}
+/// getSpecialAddressLatency - For targets where it is beneficial to
+/// backschedule instructions that compute addresses, return a value
+/// indicating the number of scheduling cycles of backscheduling that
+/// should be attempted.
+unsigned X86Subtarget::getSpecialAddressLatency() const {
+ // For x86 out-of-order targets, back-schedule address computations so
+ // that loads and stores aren't blocked.
+ // This value was chosen arbitrarily.
+ return 200;
+}
+
/// GetCpuIDAndInfo - Execute the specified cpuid and return the 4 values in the
/// specified arguments. If we can't run cpuid on the host, return true.
bool X86::GetCpuIDAndInfo(unsigned value, unsigned *rEAX, unsigned *rEBX,
Modified: llvm/trunk/lib/Target/X86/X86Subtarget.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86Subtarget.h?rev=61075&r1=61074&r2=61075&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86Subtarget.h (original)
+++ llvm/trunk/lib/Target/X86/X86Subtarget.h Mon Dec 15 21:35:01 2008
@@ -191,6 +191,12 @@
/// memset with zero passed as the second argument. Otherwise it
/// returns null.
const char *getBZeroEntry() const;
+
+ /// getSpecialAddressLatency - For targets where it is beneficial to
+ /// backschedule instructions that compute addresses, return a value
+ /// indicating the number of scheduling cycles of backscheduling that
+ /// should be attempted.
+ unsigned getSpecialAddressLatency() const;
};
namespace X86 {
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