llvm-6502/lib/Target/PowerPC/PPCHazardRecognizers.cpp

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//===-- PPCHazardRecognizers.cpp - PowerPC Hazard Recognizer Impls --------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Chris Lattner and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements hazard recognizers for scheduling on PowerPC processors.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "sched"
#include "PPCHazardRecognizers.h"
#include "PPC.h"
#include "PPCInstrInfo.h"
#include "llvm/Support/Debug.h"
#include <iostream>
using namespace llvm;
//===----------------------------------------------------------------------===//
// PowerPC 970 Hazard Recognizer
//
// This models the dispatch group formation of the PPC970 processor. Dispatch
// groups are bundles of up to five instructions that can contain various mixes
// of instructions. The PPC970 can dispatch a peak of 4 non-branch and one
// branch instruction per-cycle.
//
// There are a number of restrictions to dispatch group formation: some
// instructions can only be issued in the first slot of a dispatch group, & some
// instructions fill an entire dispatch group. Additionally, only branches can
// issue in the 5th (last) slot.
//
// Finally, there are a number of "structural" hazards on the PPC970. These
// conditions cause large performance penalties due to misprediction, recovery,
// and replay logic that has to happen. These cases include setting a CTR and
// branching through it in the same dispatch group, and storing to an address,
// then loading from the same address within a dispatch group. To avoid these
// conditions, we insert no-op instructions when appropriate.
//
// FIXME: This is missing some significant cases:
// 1. Modeling of microcoded instructions.
// 2. Handling of serialized operations.
// 3. Handling of the esoteric cases in "Resource-based Instruction Grouping".
//
PPCHazardRecognizer970::PPCHazardRecognizer970(const TargetInstrInfo &tii)
: TII(tii) {
EndDispatchGroup();
}
void PPCHazardRecognizer970::EndDispatchGroup() {
DEBUG(std::cerr << "=== Start of dispatch group\n");
NumIssued = 0;
// Structural hazard info.
HasCTRSet = false;
NumStores = 0;
}
PPCII::PPC970_Unit
PPCHazardRecognizer970::GetInstrType(unsigned Opcode,
bool &isFirst, bool &isSingle,
bool &isCracked,
bool &isLoad, bool &isStore) {
if (Opcode < ISD::BUILTIN_OP_END) {
isFirst = isSingle = isCracked = isLoad = isStore = false;
return PPCII::PPC970_Pseudo;
}
Opcode -= ISD::BUILTIN_OP_END;
const TargetInstrDescriptor &TID = TII.get(Opcode);
isLoad = TID.Flags & M_LOAD_FLAG;
isStore = TID.Flags & M_STORE_FLAG;
unsigned TSFlags = TID.TSFlags;
isFirst = TSFlags & PPCII::PPC970_First;
isSingle = TSFlags & PPCII::PPC970_Single;
isCracked = TSFlags & PPCII::PPC970_Cracked;
return (PPCII::PPC970_Unit)(TSFlags & PPCII::PPC970_Mask);
}
/// isLoadOfStoredAddress - If we have a load from the previously stored pointer
/// as indicated by StorePtr1/StorePtr2/StoreSize, return true.
bool PPCHazardRecognizer970::
isLoadOfStoredAddress(unsigned LoadSize, SDOperand Ptr1, SDOperand Ptr2) const {
for (unsigned i = 0, e = NumStores; i != e; ++i) {
// Handle exact and commuted addresses.
if (Ptr1 == StorePtr1[i] && Ptr2 == StorePtr2[i])
return true;
if (Ptr2 == StorePtr1[i] && Ptr1 == StorePtr2[i])
return true;
// Okay, we don't have an exact match, if this is an indexed offset, see if
// we have overlap (which happens during fp->int conversion for example).
if (StorePtr2[i] == Ptr2) {
if (ConstantSDNode *StoreOffset = dyn_cast<ConstantSDNode>(StorePtr1[i]))
if (ConstantSDNode *LoadOffset = dyn_cast<ConstantSDNode>(Ptr1)) {
// Okay the base pointers match, so we have [c1+r] vs [c2+r]. Check
// to see if the load and store actually overlap.
int StoreOffs = StoreOffset->getValue();
int LoadOffs = LoadOffset->getValue();
if (StoreOffs < LoadOffs) {
if (int(StoreOffs+StoreSize[i]) > LoadOffs) return true;
} else {
if (int(LoadOffs+LoadSize) > StoreOffs) return true;
}
}
}
}
return false;
}
/// getHazardType - We return hazard for any non-branch instruction that would
/// terminate terminate the dispatch group. We turn NoopHazard for any
/// instructions that wouldn't terminate the dispatch group that would cause a
/// pipeline flush.
HazardRecognizer::HazardType PPCHazardRecognizer970::
getHazardType(SDNode *Node) {
bool isFirst, isSingle, isCracked, isLoad, isStore;
PPCII::PPC970_Unit InstrType =
GetInstrType(Node->getOpcode(), isFirst, isSingle, isCracked,
isLoad, isStore);
if (InstrType == PPCII::PPC970_Pseudo) return NoHazard;
unsigned Opcode = Node->getOpcode()-ISD::BUILTIN_OP_END;
// We can only issue a PPC970_First/PPC970_Single instruction (such as
// crand/mtspr/etc) if this is the first cycle of the dispatch group.
if (NumIssued != 0 && (isFirst || isSingle))
return Hazard;
// If this instruction is cracked into two ops by the decoder, we know that
// it is not a branch and that it cannot issue if 3 other instructions are
// already in the dispatch group.
if (isCracked && NumIssued > 2)
return Hazard;
switch (InstrType) {
default: assert(0 && "Unknown instruction type!");
case PPCII::PPC970_FXU:
case PPCII::PPC970_LSU:
case PPCII::PPC970_FPU:
case PPCII::PPC970_VALU:
case PPCII::PPC970_VPERM:
// We can only issue a branch as the last instruction in a group.
if (NumIssued == 4) return Hazard;
break;
case PPCII::PPC970_CRU:
// We can only issue a CR instruction in the first two slots.
if (NumIssued >= 2) return Hazard;
break;
case PPCII::PPC970_BRU:
break;
}
// Do not allow MTCTR and BCTRL to be in the same dispatch group.
if (HasCTRSet && Opcode == PPC::BCTRL)
return NoopHazard;
// If this is a load following a store, make sure it's not to the same or
// overlapping address.
if (isLoad && NumStores) {
unsigned LoadSize;
switch (Opcode) {
default: assert(0 && "Unknown load!");
case PPC::LBZ:
case PPC::LBZX:
case PPC::LBZ8:
case PPC::LBZX8:
case PPC::LVEBX:
LoadSize = 1;
break;
case PPC::LHA:
case PPC::LHAX:
case PPC::LHZ:
case PPC::LHZX:
case PPC::LVEHX:
case PPC::LHBRX:
case PPC::LHA8:
case PPC::LHAX8:
case PPC::LHZ8:
case PPC::LHZX8:
LoadSize = 2;
break;
case PPC::LFS:
case PPC::LFSX:
case PPC::LWZ:
case PPC::LWZX:
case PPC::LWZU:
case PPC::LWA:
case PPC::LWAX:
case PPC::LVEWX:
case PPC::LWBRX:
case PPC::LWZ8:
case PPC::LWZX8:
LoadSize = 4;
break;
case PPC::LFD:
case PPC::LFDX:
case PPC::LD:
case PPC::LDX:
LoadSize = 8;
break;
case PPC::LVX:
LoadSize = 16;
break;
}
if (isLoadOfStoredAddress(LoadSize,
Node->getOperand(0), Node->getOperand(1)))
return NoopHazard;
}
return NoHazard;
}
void PPCHazardRecognizer970::EmitInstruction(SDNode *Node) {
bool isFirst, isSingle, isCracked, isLoad, isStore;
PPCII::PPC970_Unit InstrType =
GetInstrType(Node->getOpcode(), isFirst, isSingle, isCracked,
isLoad, isStore);
if (InstrType == PPCII::PPC970_Pseudo) return;
unsigned Opcode = Node->getOpcode()-ISD::BUILTIN_OP_END;
// Update structural hazard information.
if (Opcode == PPC::MTCTR) HasCTRSet = true;
// Track the address stored to.
if (isStore) {
unsigned ThisStoreSize;
switch (Opcode) {
default: assert(0 && "Unknown store instruction!");
case PPC::STB:
case PPC::STBX:
case PPC::STB8:
case PPC::STBX8:
case PPC::STVEBX:
ThisStoreSize = 1;
break;
case PPC::STH:
case PPC::STHX:
case PPC::STH8:
case PPC::STHX8:
case PPC::STVEHX:
case PPC::STHBRX:
ThisStoreSize = 2;
break;
case PPC::STFS:
case PPC::STFSX:
case PPC::STWU:
case PPC::STWX:
case PPC::STWUX:
case PPC::STW:
case PPC::STW8:
case PPC::STWX8:
case PPC::STVEWX:
case PPC::STFIWX:
case PPC::STWBRX:
ThisStoreSize = 4;
break;
case PPC::STD_32:
case PPC::STDX_32:
case PPC::STD:
case PPC::STFD:
case PPC::STFDX:
case PPC::STDX:
case PPC::STDUX:
ThisStoreSize = 8;
break;
case PPC::STVX:
ThisStoreSize = 16;
break;
}
StoreSize[NumStores] = ThisStoreSize;
StorePtr1[NumStores] = Node->getOperand(1);
StorePtr2[NumStores] = Node->getOperand(2);
++NumStores;
}
if (InstrType == PPCII::PPC970_BRU || isSingle)
NumIssued = 4; // Terminate a d-group.
++NumIssued;
// If this instruction is cracked into two ops by the decoder, remember that
// we issued two pieces.
if (isCracked)
++NumIssued;
if (NumIssued == 5)
EndDispatchGroup();
}
void PPCHazardRecognizer970::AdvanceCycle() {
assert(NumIssued < 5 && "Illegal dispatch group!");
++NumIssued;
if (NumIssued == 5)
EndDispatchGroup();
}
void PPCHazardRecognizer970::EmitNoop() {
AdvanceCycle();
}