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/Support/TargetRegistry.h"
14 #include "llvm/Transforms/Scalar.h"
15 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
16 
17 using namespace llvm;
18 
19 extern "C" void LLVMInitializeSystemZTarget() {
20   // Register the target.
21   RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
22 }
23 
24 SystemZTargetMachine::SystemZTargetMachine(const Target &T, StringRef TT,
25                                            StringRef CPU, StringRef FS,
26                                            const TargetOptions &Options,
27                                            Reloc::Model RM, CodeModel::Model CM,
28                                            CodeGenOpt::Level OL)
29     // Make sure that global data has at least 16 bits of alignment by
30     // default, so that we can refer to it using LARL.  We don't have any
31     // special requirements for stack variables though.
32     : LLVMTargetMachine(T, "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64",
33                         TT, CPU, FS, Options, RM, CM, OL),
34       TLOF(make_unique<TargetLoweringObjectFileELF>()),
35       Subtarget(TT, CPU, FS, *this) {
36   initAsmInfo();
37 }
38 
39 SystemZTargetMachine::~SystemZTargetMachine() {}
40 
41 namespace {
42 /// SystemZ Code Generator Pass Configuration Options.
43 class SystemZPassConfig : public TargetPassConfig {
44 public:
45   SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
46     : TargetPassConfig(TM, PM) {}
47 
48   SystemZTargetMachine &getSystemZTargetMachine() const {
49     return getTM<SystemZTargetMachine>();
50   }
51 
52   void addIRPasses() override;
53   bool addInstSelector() override;
54   void addPreSched2() override;
55   void addPreEmitPass() override;
56 };
57 } // end anonymous namespace
58 
59 void SystemZPassConfig::addIRPasses() {
60   TargetPassConfig::addIRPasses();
61 }
62 
63 bool SystemZPassConfig::addInstSelector() {
64   addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
65 
66  if (getOptLevel() != CodeGenOpt::None)
67     addPass(createSystemZLDCleanupPass(getSystemZTargetMachine()));
68 
69   return false;
70 }
71 
72 void SystemZPassConfig::addPreSched2() {
73   if (getOptLevel() != CodeGenOpt::None &&
74       getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
75     addPass(&IfConverterID);
76 }
77 
78 void SystemZPassConfig::addPreEmitPass() {
79   // We eliminate comparisons here rather than earlier because some
80   // transformations can change the set of available CC values and we
81   // generally want those transformations to have priority.  This is
82   // especially true in the commonest case where the result of the comparison
83   // is used by a single in-range branch instruction, since we will then
84   // be able to fuse the compare and the branch instead.
85   //
86   // For example, two-address NILF can sometimes be converted into
87   // three-address RISBLG.  NILF produces a CC value that indicates whether
88   // the low word is zero, but RISBLG does not modify CC at all.  On the
89   // other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
90   // The CC value produced by NILL isn't useful for our purposes, but the
91   // value produced by RISBG can be used for any comparison with zero
92   // (not just equality).  So there are some transformations that lose
93   // CC values (while still being worthwhile) and others that happen to make
94   // the CC result more useful than it was originally.
95   //
96   // Another reason is that we only want to use BRANCH ON COUNT in cases
97   // where we know that the count register is not going to be spilled.
98   //
99   // Doing it so late makes it more likely that a register will be reused
100   // between the comparison and the branch, but it isn't clear whether
101   // preventing that would be a win or not.
102   if (getOptLevel() != CodeGenOpt::None)
103     addPass(createSystemZElimComparePass(getSystemZTargetMachine()), false);
104   if (getOptLevel() != CodeGenOpt::None)
105     addPass(createSystemZShortenInstPass(getSystemZTargetMachine()), false);
106   addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
107 }
108 
109 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
110   return new SystemZPassConfig(this, PM);
111 }
112 
113 TargetIRAnalysis SystemZTargetMachine::getTargetIRAnalysis() {
114   return TargetIRAnalysis([this](Function &F) {
115     return TargetTransformInfo(SystemZTTIImpl(this, F));
116   });
117 }
118