1 //===-- PPCHazardRecognizers.cpp - PowerPC Hazard Recognizer Impls --------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by Chris Lattner and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements hazard recognizers for scheduling on PowerPC processors.
12 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "sched"
15 #include "PPCHazardRecognizers.h"
17 #include "llvm/Support/Debug.h"
22 //===----------------------------------------------------------------------===//
23 // PowerPC 970 Hazard Recognizer
25 // This models the dispatch group formation of the PPC970 processor. Dispatch
26 // groups are bundles of up to five instructions that can contain up to two ALU
27 // (aka FXU) ops, two FPU ops, two Load/Store ops, one CR op, one VALU op, one
28 // VPERM op, and one BRANCH op. If the code contains more instructions in a
29 // sequence than the dispatch group can contain (e.g. three loads in a row) the
30 // processor terminates the dispatch group early, wasting execution resources.
32 // In addition to these restrictions, there are a number of other restrictions:
33 // some instructions, e.g. branches, are required to be the last instruction in
34 // a group. Additionally, only branches can issue in the 5th (last) slot.
36 // Finally, there are a number of "structural" hazards on the PPC970. These
37 // conditions cause large performance penalties due to misprediction, recovery,
38 // and replay logic that has to happen. These cases include setting a CTR and
39 // branching through it in the same dispatch group, and storing to an address,
40 // then loading from the same address within a dispatch group. To avoid these
41 // conditions, we insert no-op instructions when appropriate.
43 // FIXME: This is missing some significant cases:
44 // -1. Handle all of the instruction types in GetInstrType.
45 // 0. Handling of instructions that must be the first/last in a group.
46 // 1. Modeling of microcoded instructions.
47 // 2. Handling of cracked instructions.
48 // 3. Handling of serialized operations.
49 // 4. Handling of the esoteric cases in "Resource-based Instruction Grouping",
50 // e.g. integer divides that only execute in the second slot.
53 void PPCHazardRecognizer970::EndDispatchGroup() {
54 DEBUG(std::cerr << "=== Start of dispatch group\n");
56 NumFXU = NumLSU = NumFPU = 0;
57 HasCR = HasVALU = HasVPERM = false;
60 // Structural hazard info.
62 StorePtr1 = StorePtr2 = SDOperand();
67 PPCHazardRecognizer970::PPC970InstrType
68 PPCHazardRecognizer970::GetInstrType(unsigned Opcode) {
69 if (Opcode < ISD::BUILTIN_OP_END)
71 Opcode -= ISD::BUILTIN_OP_END;
74 case PPC::FMRSD: return PseudoInst; // Usually coallesced away.
99 /// StartBasicBlock - Initiate a new dispatch group.
100 void PPCHazardRecognizer970::StartBasicBlock() {
104 /// isLoadOfStoredAddress - If we have a load from the previously stored pointer
105 /// as indicated by StorePtr1/StorePtr2/StoreSize, return true.
106 bool PPCHazardRecognizer970::
107 isLoadOfStoredAddress(unsigned LoadSize, SDOperand Ptr1, SDOperand Ptr2) const {
108 // Handle exact and commuted addresses.
109 if (Ptr1 == StorePtr1 && Ptr2 == StorePtr2)
111 if (Ptr2 == StorePtr1 && Ptr1 == StorePtr2)
114 // Okay, we don't have an exact match, if this is an indexed offset, see if we
115 // have overlap (which happens during fp->int conversion for example).
116 if (StorePtr2 == Ptr2) {
117 if (ConstantSDNode *StoreOffset = dyn_cast<ConstantSDNode>(StorePtr1))
118 if (ConstantSDNode *LoadOffset = dyn_cast<ConstantSDNode>(Ptr1)) {
119 // Okay the base pointers match, so we have [c1+r] vs [c2+r]. Check to
120 // see if the load and store actually overlap.
121 int StoreOffs = StoreOffset->getValue();
122 int LoadOffs = LoadOffset->getValue();
123 if (StoreOffs < LoadOffs) {
124 if (int(StoreOffs+StoreSize) > LoadOffs) return true;
126 if (int(LoadOffs+LoadSize) > StoreOffs) return true;
133 /// getHazardType - We return hazard for any non-branch instruction that would
134 /// terminate terminate the dispatch group. We turn NoopHazard for any
135 /// instructions that wouldn't terminate the dispatch group that would cause a
137 HazardRecognizer::HazardType PPCHazardRecognizer970::
138 getHazardType(SDNode *Node) {
139 PPC970InstrType InstrType = GetInstrType(Node->getOpcode());
140 if (InstrType == PseudoInst) return NoHazard;
141 unsigned Opcode = Node->getOpcode()-ISD::BUILTIN_OP_END;
144 default: assert(0 && "Unknown instruction type!");
145 case FXU: if (NumFXU == 2) return Hazard;
147 case LSU_LD: if (NumLSU == 2) return Hazard;
148 case FPU: if (NumFPU == 2) return Hazard;
149 case CR: if (HasCR) return Hazard;
150 case VALU: if (HasVALU) return Hazard;
151 case VPERM: if (HasVPERM) return Hazard;
155 // We can only issue a branch as the last instruction in a group.
156 if (NumIssued == 4 && InstrType != BR)
159 // Do not allow MTCTR and BCTRL to be in the same dispatch group.
160 if (HasCTRSet && Opcode == PPC::BCTRL)
163 // If this is a load following a store, make sure it's not to the same or
164 // overlapping address.
165 if (InstrType == LSU_LD && StoreSize) {
168 default: assert(0 && "Unknown load!");
172 case PPC::LWZ: LoadSize = 4; break;
173 case PPC::LFD: LoadSize = 8; break;
176 if (isLoadOfStoredAddress(LoadSize,
177 Node->getOperand(0), Node->getOperand(1)))
184 void PPCHazardRecognizer970::EmitInstruction(SDNode *Node) {
185 PPC970InstrType InstrType = GetInstrType(Node->getOpcode());
186 if (InstrType == PseudoInst) return;
187 unsigned Opcode = Node->getOpcode()-ISD::BUILTIN_OP_END;
189 // Update structural hazard information.
190 if (Opcode == PPC::MTCTR) HasCTRSet = true;
192 // Track the address stored to.
193 if (InstrType == LSU_ST) {
194 StorePtr1 = Node->getOperand(1);
195 StorePtr2 = Node->getOperand(2);
197 default: assert(0 && "Unknown store instruction!");
198 case PPC::STFD: StoreSize = 8; break;
199 case PPC::STW: StoreSize = 4; break;
204 default: assert(0 && "Unknown instruction type!");
205 case FXU: ++NumFXU; break;
207 case LSU_ST: ++NumLSU; break;
208 case FPU: ++NumFPU; break;
209 case CR: HasCR = true; break;
210 case VALU: HasVALU = true; break;
211 case VPERM: HasVPERM = true; break;
212 case BR: NumIssued = 4; return; // ends a d-group.
220 void PPCHazardRecognizer970::AdvanceCycle() {
221 assert(NumIssued < 5 && "Illegal dispatch group!");
227 void PPCHazardRecognizer970::EmitNoop() {