1 //===-- SystemZTargetMachine.cpp - Define TargetMachine for SystemZ -------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "SystemZTargetMachine.h"
11 #include "SystemZTargetTransformInfo.h"
12 #include "llvm/CodeGen/Passes.h"
13 #include "llvm/CodeGen/TargetPassConfig.h"
14 #include "llvm/Support/TargetRegistry.h"
15 #include "llvm/Transforms/Scalar.h"
16 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
17 
18 using namespace llvm;
19 
20 extern cl::opt<bool> MISchedPostRA;
21 extern "C" void LLVMInitializeSystemZTarget() {
22   // Register the target.
23   RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
24 }
25 
26 // Determine whether we use the vector ABI.
27 static bool UsesVectorABI(StringRef CPU, StringRef FS) {
28   // We use the vector ABI whenever the vector facility is avaiable.
29   // This is the case by default if CPU is z13 or later, and can be
30   // overridden via "[+-]vector" feature string elements.
31   bool VectorABI = true;
32   if (CPU.empty() || CPU == "generic" ||
33       CPU == "z10" || CPU == "z196" || CPU == "zEC12")
34     VectorABI = false;
35 
36   SmallVector<StringRef, 3> Features;
37   FS.split(Features, ',', -1, false /* KeepEmpty */);
38   for (auto &Feature : Features) {
39     if (Feature == "vector" || Feature == "+vector")
40       VectorABI = true;
41     if (Feature == "-vector")
42       VectorABI = false;
43   }
44 
45   return VectorABI;
46 }
47 
48 static std::string computeDataLayout(const Triple &TT, StringRef CPU,
49                                      StringRef FS) {
50   bool VectorABI = UsesVectorABI(CPU, FS);
51   std::string Ret = "";
52 
53   // Big endian.
54   Ret += "E";
55 
56   // Data mangling.
57   Ret += DataLayout::getManglingComponent(TT);
58 
59   // Make sure that global data has at least 16 bits of alignment by
60   // default, so that we can refer to it using LARL.  We don't have any
61   // special requirements for stack variables though.
62   Ret += "-i1:8:16-i8:8:16";
63 
64   // 64-bit integers are naturally aligned.
65   Ret += "-i64:64";
66 
67   // 128-bit floats are aligned only to 64 bits.
68   Ret += "-f128:64";
69 
70   // When using the vector ABI, 128-bit vectors are also aligned to 64 bits.
71   if (VectorABI)
72     Ret += "-v128:64";
73 
74   // We prefer 16 bits of aligned for all globals; see above.
75   Ret += "-a:8:16";
76 
77   // Integer registers are 32 or 64 bits.
78   Ret += "-n32:64";
79 
80   return Ret;
81 }
82 
83 SystemZTargetMachine::SystemZTargetMachine(const Target &T, const Triple &TT,
84                                            StringRef CPU, StringRef FS,
85                                            const TargetOptions &Options,
86                                            Reloc::Model RM, CodeModel::Model CM,
87                                            CodeGenOpt::Level OL)
88     : LLVMTargetMachine(T, computeDataLayout(TT, CPU, FS), TT, CPU, FS, Options,
89                         RM, CM, OL),
90       TLOF(make_unique<TargetLoweringObjectFileELF>()),
91       Subtarget(TT, CPU, FS, *this) {
92   initAsmInfo();
93 }
94 
95 SystemZTargetMachine::~SystemZTargetMachine() {}
96 
97 namespace {
98 /// SystemZ Code Generator Pass Configuration Options.
99 class SystemZPassConfig : public TargetPassConfig {
100 public:
101   SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
102     : TargetPassConfig(TM, PM) {}
103 
104   SystemZTargetMachine &getSystemZTargetMachine() const {
105     return getTM<SystemZTargetMachine>();
106   }
107 
108   void addIRPasses() override;
109   bool addInstSelector() override;
110   void addPreSched2() override;
111   void addPreEmitPass() override;
112 };
113 } // end anonymous namespace
114 
115 void SystemZPassConfig::addIRPasses() {
116   TargetPassConfig::addIRPasses();
117 }
118 
119 bool SystemZPassConfig::addInstSelector() {
120   addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
121 
122  if (getOptLevel() != CodeGenOpt::None)
123     addPass(createSystemZLDCleanupPass(getSystemZTargetMachine()));
124 
125   return false;
126 }
127 
128 void SystemZPassConfig::addPreSched2() {
129   if (getOptLevel() != CodeGenOpt::None)
130     addPass(&IfConverterID);
131 }
132 
133 void SystemZPassConfig::addPreEmitPass() {
134 
135   // Do instruction shortening before compare elimination because some
136   // vector instructions will be shortened into opcodes that compare
137   // elimination recognizes.
138   if (getOptLevel() != CodeGenOpt::None)
139     addPass(createSystemZShortenInstPass(getSystemZTargetMachine()), false);
140 
141   // We eliminate comparisons here rather than earlier because some
142   // transformations can change the set of available CC values and we
143   // generally want those transformations to have priority.  This is
144   // especially true in the commonest case where the result of the comparison
145   // is used by a single in-range branch instruction, since we will then
146   // be able to fuse the compare and the branch instead.
147   //
148   // For example, two-address NILF can sometimes be converted into
149   // three-address RISBLG.  NILF produces a CC value that indicates whether
150   // the low word is zero, but RISBLG does not modify CC at all.  On the
151   // other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
152   // The CC value produced by NILL isn't useful for our purposes, but the
153   // value produced by RISBG can be used for any comparison with zero
154   // (not just equality).  So there are some transformations that lose
155   // CC values (while still being worthwhile) and others that happen to make
156   // the CC result more useful than it was originally.
157   //
158   // Another reason is that we only want to use BRANCH ON COUNT in cases
159   // where we know that the count register is not going to be spilled.
160   //
161   // Doing it so late makes it more likely that a register will be reused
162   // between the comparison and the branch, but it isn't clear whether
163   // preventing that would be a win or not.
164   if (getOptLevel() != CodeGenOpt::None)
165     addPass(createSystemZElimComparePass(getSystemZTargetMachine()), false);
166   addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
167 
168   // Do final scheduling after all other optimizations, to get an
169   // optimal input for the decoder (branch relaxation must happen
170   // after block placement).
171   if (getOptLevel() != CodeGenOpt::None) {
172     if (MISchedPostRA)
173       addPass(&PostMachineSchedulerID);
174     else
175       addPass(&PostRASchedulerID);
176   }
177 }
178 
179 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
180   return new SystemZPassConfig(this, PM);
181 }
182 
183 TargetIRAnalysis SystemZTargetMachine::getTargetIRAnalysis() {
184   return TargetIRAnalysis([this](const Function &F) {
185     return TargetTransformInfo(SystemZTTIImpl(this, F));
186   });
187 }
188