1 //===-- PowerPCSubtarget.cpp - PPC Subtarget Information ------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the PPC specific subclass of TargetSubtargetInfo.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "PPCSubtarget.h"
14 #include "PPC.h"
15 #include "PPCRegisterInfo.h"
16 #include "PPCTargetMachine.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/CodeGen/MachineScheduler.h"
19 #include "llvm/IR/Attributes.h"
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/GlobalValue.h"
22 #include "llvm/Support/CommandLine.h"
23 #include "llvm/Support/TargetRegistry.h"
24 #include "llvm/Target/TargetMachine.h"
25 #include <cstdlib>
26 
27 using namespace llvm;
28 
29 #define DEBUG_TYPE "ppc-subtarget"
30 
31 #define GET_SUBTARGETINFO_TARGET_DESC
32 #define GET_SUBTARGETINFO_CTOR
33 #include "PPCGenSubtargetInfo.inc"
34 
35 static cl::opt<bool> UseSubRegLiveness("ppc-track-subreg-liveness",
36 cl::desc("Enable subregister liveness tracking for PPC"), cl::Hidden);
37 
38 static cl::opt<bool> QPXStackUnaligned("qpx-stack-unaligned",
39   cl::desc("Even when QPX is enabled the stack is not 32-byte aligned"),
40   cl::Hidden);
41 
42 PPCSubtarget &PPCSubtarget::initializeSubtargetDependencies(StringRef CPU,
43                                                             StringRef FS) {
44   initializeEnvironment();
45   initSubtargetFeatures(CPU, FS);
46   return *this;
47 }
48 
49 PPCSubtarget::PPCSubtarget(const Triple &TT, const std::string &CPU,
50                            const std::string &FS, const PPCTargetMachine &TM)
51     : PPCGenSubtargetInfo(TT, CPU, FS), TargetTriple(TT),
52       IsPPC64(TargetTriple.getArch() == Triple::ppc64 ||
53               TargetTriple.getArch() == Triple::ppc64le),
54       TM(TM), FrameLowering(initializeSubtargetDependencies(CPU, FS)),
55       InstrInfo(*this), TLInfo(TM, *this) {}
56 
57 void PPCSubtarget::initializeEnvironment() {
58   StackAlignment = 16;
59   DarwinDirective = PPC::DIR_NONE;
60   HasMFOCRF = false;
61   Has64BitSupport = false;
62   Use64BitRegs = false;
63   UseCRBits = false;
64   HasHardFloat = false;
65   HasAltivec = false;
66   HasSPE = false;
67   HasFPU = false;
68   HasQPX = false;
69   HasVSX = false;
70   HasP8Vector = false;
71   HasP8Altivec = false;
72   HasP8Crypto = false;
73   HasP9Vector = false;
74   HasP9Altivec = false;
75   HasFCPSGN = false;
76   HasFSQRT = false;
77   HasFRE = false;
78   HasFRES = false;
79   HasFRSQRTE = false;
80   HasFRSQRTES = false;
81   HasRecipPrec = false;
82   HasSTFIWX = false;
83   HasLFIWAX = false;
84   HasFPRND = false;
85   HasFPCVT = false;
86   HasISEL = false;
87   HasBPERMD = false;
88   HasExtDiv = false;
89   HasCMPB = false;
90   HasLDBRX = false;
91   IsBookE = false;
92   HasOnlyMSYNC = false;
93   IsPPC4xx = false;
94   IsPPC6xx = false;
95   IsE500 = false;
96   FeatureMFTB = false;
97   DeprecatedDST = false;
98   HasLazyResolverStubs = false;
99   HasICBT = false;
100   HasInvariantFunctionDescriptors = false;
101   HasPartwordAtomics = false;
102   HasDirectMove = false;
103   IsQPXStackUnaligned = false;
104   HasHTM = false;
105   HasFusion = false;
106   HasFloat128 = false;
107   IsISA3_0 = false;
108   UseLongCalls = false;
109   SecurePlt = false;
110   VectorsUseTwoUnits = false;
111   UsePPCPreRASchedStrategy = false;
112   UsePPCPostRASchedStrategy = false;
113 
114   HasPOPCNTD = POPCNTD_Unavailable;
115 }
116 
117 void PPCSubtarget::initSubtargetFeatures(StringRef CPU, StringRef FS) {
118   // Determine default and user specified characteristics
119   std::string CPUName = CPU;
120   if (CPUName.empty() || CPU == "generic") {
121     // If cross-compiling with -march=ppc64le without -mcpu
122     if (TargetTriple.getArch() == Triple::ppc64le)
123       CPUName = "ppc64le";
124     else
125       CPUName = "generic";
126   }
127 
128   // Initialize scheduling itinerary for the specified CPU.
129   InstrItins = getInstrItineraryForCPU(CPUName);
130 
131   // Parse features string.
132   ParseSubtargetFeatures(CPUName, FS);
133 
134   // If the user requested use of 64-bit regs, but the cpu selected doesn't
135   // support it, ignore.
136   if (IsPPC64 && has64BitSupport())
137     Use64BitRegs = true;
138 
139   // Set up darwin-specific properties.
140   if (isDarwin())
141     HasLazyResolverStubs = true;
142 
143   if (TargetTriple.isOSNetBSD() || TargetTriple.isOSOpenBSD())
144     SecurePlt = true;
145 
146   if (HasSPE && IsPPC64)
147     report_fatal_error( "SPE is only supported for 32-bit targets.\n", false);
148   if (HasSPE && (HasAltivec || HasQPX || HasVSX || HasFPU))
149     report_fatal_error(
150         "SPE and traditional floating point cannot both be enabled.\n", false);
151 
152   // If not SPE, set standard FPU
153   if (!HasSPE)
154     HasFPU = true;
155 
156   // QPX requires a 32-byte aligned stack. Note that we need to do this if
157   // we're compiling for a BG/Q system regardless of whether or not QPX
158   // is enabled because external functions will assume this alignment.
159   IsQPXStackUnaligned = QPXStackUnaligned;
160   StackAlignment = getPlatformStackAlignment();
161 
162   // Determine endianness.
163   // FIXME: Part of the TargetMachine.
164   IsLittleEndian = (TargetTriple.getArch() == Triple::ppc64le);
165 }
166 
167 /// Return true if accesses to the specified global have to go through a dyld
168 /// lazy resolution stub.  This means that an extra load is required to get the
169 /// address of the global.
170 bool PPCSubtarget::hasLazyResolverStub(const GlobalValue *GV) const {
171   if (!HasLazyResolverStubs)
172     return false;
173   if (!TM.shouldAssumeDSOLocal(*GV->getParent(), GV))
174     return true;
175   // 32 bit macho has no relocation for a-b if a is undefined, even if b is in
176   // the section that is being relocated. This means we have to use o load even
177   // for GVs that are known to be local to the dso.
178   if (GV->isDeclarationForLinker() || GV->hasCommonLinkage())
179     return true;
180   return false;
181 }
182 
183 bool PPCSubtarget::enableMachineScheduler() const {
184   return true;
185 }
186 
187 // This overrides the PostRAScheduler bit in the SchedModel for each CPU.
188 bool PPCSubtarget::enablePostRAScheduler() const { return true; }
189 
190 PPCGenSubtargetInfo::AntiDepBreakMode PPCSubtarget::getAntiDepBreakMode() const {
191   return TargetSubtargetInfo::ANTIDEP_ALL;
192 }
193 
194 void PPCSubtarget::getCriticalPathRCs(RegClassVector &CriticalPathRCs) const {
195   CriticalPathRCs.clear();
196   CriticalPathRCs.push_back(isPPC64() ?
197                             &PPC::G8RCRegClass : &PPC::GPRCRegClass);
198 }
199 
200 void PPCSubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
201                                        unsigned NumRegionInstrs) const {
202   // The GenericScheduler that we use defaults to scheduling bottom up only.
203   // We want to schedule from both the top and the bottom and so we set
204   // OnlyBottomUp to false.
205   // We want to do bi-directional scheduling since it provides a more balanced
206   // schedule leading to better performance.
207   Policy.OnlyBottomUp = false;
208   // Spilling is generally expensive on all PPC cores, so always enable
209   // register-pressure tracking.
210   Policy.ShouldTrackPressure = true;
211 }
212 
213 bool PPCSubtarget::useAA() const {
214   return true;
215 }
216 
217 bool PPCSubtarget::enableSubRegLiveness() const {
218   return UseSubRegLiveness;
219 }
220 
221 unsigned char
222 PPCSubtarget::classifyGlobalReference(const GlobalValue *GV) const {
223   // Note that currently we don't generate non-pic references.
224   // If a caller wants that, this will have to be updated.
225 
226   // Large code model always uses the TOC even for local symbols.
227   if (TM.getCodeModel() == CodeModel::Large)
228     return PPCII::MO_PIC_FLAG | PPCII::MO_NLP_FLAG;
229 
230   if (TM.shouldAssumeDSOLocal(*GV->getParent(), GV))
231     return PPCII::MO_PIC_FLAG;
232   return PPCII::MO_PIC_FLAG | PPCII::MO_NLP_FLAG;
233 }
234 
235 bool PPCSubtarget::isELFv2ABI() const { return TM.isELFv2ABI(); }
236 bool PPCSubtarget::isPPC64() const { return TM.isPPC64(); }
237