SystemZTargetMachine.cpp revision cd81d94322a39503e4a3e87b6ee03d4fcb3465fb 
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 "llvm/CodeGen/Passes.h"
12#include "llvm/Support/TargetRegistry.h"
13#include "llvm/Transforms/Scalar.h"
14
15using namespace llvm;
16
17extern "C" void LLVMInitializeSystemZTarget() {
18  // Register the target.
19  RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
20}
21
22SystemZTargetMachine::SystemZTargetMachine(const Target &T, StringRef TT,
23                                           StringRef CPU, StringRef FS,
24                                           const TargetOptions &Options,
25                                           Reloc::Model RM, CodeModel::Model CM,
26                                           CodeGenOpt::Level OL)
27    : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
28      Subtarget(TT, CPU, FS, *this) {
29  initAsmInfo();
30}
31
32namespace {
33/// SystemZ Code Generator Pass Configuration Options.
34class SystemZPassConfig : public TargetPassConfig {
35public:
36  SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
37    : TargetPassConfig(TM, PM) {}
38
39  SystemZTargetMachine &getSystemZTargetMachine() const {
40    return getTM<SystemZTargetMachine>();
41  }
42
43  void addIRPasses() override;
44  bool addInstSelector() override;
45  bool addPreSched2() override;
46  bool addPreEmitPass() override;
47};
48} // end anonymous namespace
49
50void SystemZPassConfig::addIRPasses() {
51  TargetPassConfig::addIRPasses();
52  addPass(createPartiallyInlineLibCallsPass());
53}
54
55bool SystemZPassConfig::addInstSelector() {
56  addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
57  return false;
58}
59
60bool SystemZPassConfig::addPreSched2() {
61  if (getOptLevel() != CodeGenOpt::None &&
62      getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
63    addPass(&IfConverterID);
64  return true;
65}
66
67bool SystemZPassConfig::addPreEmitPass() {
68  // We eliminate comparisons here rather than earlier because some
69  // transformations can change the set of available CC values and we
70  // generally want those transformations to have priority.  This is
71  // especially true in the commonest case where the result of the comparison
72  // is used by a single in-range branch instruction, since we will then
73  // be able to fuse the compare and the branch instead.
74  //
75  // For example, two-address NILF can sometimes be converted into
76  // three-address RISBLG.  NILF produces a CC value that indicates whether
77  // the low word is zero, but RISBLG does not modify CC at all.  On the
78  // other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
79  // The CC value produced by NILL isn't useful for our purposes, but the
80  // value produced by RISBG can be used for any comparison with zero
81  // (not just equality).  So there are some transformations that lose
82  // CC values (while still being worthwhile) and others that happen to make
83  // the CC result more useful than it was originally.
84  //
85  // Another reason is that we only want to use BRANCH ON COUNT in cases
86  // where we know that the count register is not going to be spilled.
87  //
88  // Doing it so late makes it more likely that a register will be reused
89  // between the comparison and the branch, but it isn't clear whether
90  // preventing that would be a win or not.
91  if (getOptLevel() != CodeGenOpt::None)
92    addPass(createSystemZElimComparePass(getSystemZTargetMachine()));
93  if (getOptLevel() != CodeGenOpt::None)
94    addPass(createSystemZShortenInstPass(getSystemZTargetMachine()));
95  addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
96  return true;
97}
98
99TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
100  return new SystemZPassConfig(this, PM);
101}
102