SystemZTargetMachine.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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,
26                                           CodeModel::Model CM,
27                                           CodeGenOpt::Level OL)
28  : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
29    Subtarget(TT, CPU, FS),
30    // Make sure that global data has at least 16 bits of alignment by default,
31    // so that we can refer to it using LARL.  We don't have any special
32    // requirements for stack variables though.
33    DL("E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-a:8:16-n32:64"),
34    InstrInfo(*this), TLInfo(*this), TSInfo(*this),
35    FrameLowering(*this, Subtarget) {
36  initAsmInfo();
37}
38
39namespace {
40/// SystemZ Code Generator Pass Configuration Options.
41class SystemZPassConfig : public TargetPassConfig {
42public:
43  SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
44    : TargetPassConfig(TM, PM) {}
45
46  SystemZTargetMachine &getSystemZTargetMachine() const {
47    return getTM<SystemZTargetMachine>();
48  }
49
50  void addIRPasses() override;
51  bool addInstSelector() override;
52  bool addPreSched2() override;
53  bool addPreEmitPass() override;
54};
55} // end anonymous namespace
56
57void SystemZPassConfig::addIRPasses() {
58  TargetPassConfig::addIRPasses();
59  addPass(createPartiallyInlineLibCallsPass());
60}
61
62bool SystemZPassConfig::addInstSelector() {
63  addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
64  return false;
65}
66
67bool SystemZPassConfig::addPreSched2() {
68  if (getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
69    addPass(&IfConverterID);
70  return true;
71}
72
73bool SystemZPassConfig::addPreEmitPass() {
74  // We eliminate comparisons here rather than earlier because some
75  // transformations can change the set of available CC values and we
76  // generally want those transformations to have priority.  This is
77  // especially true in the commonest case where the result of the comparison
78  // is used by a single in-range branch instruction, since we will then
79  // be able to fuse the compare and the branch instead.
80  //
81  // For example, two-address NILF can sometimes be converted into
82  // three-address RISBLG.  NILF produces a CC value that indicates whether
83  // the low word is zero, but RISBLG does not modify CC at all.  On the
84  // other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
85  // The CC value produced by NILL isn't useful for our purposes, but the
86  // value produced by RISBG can be used for any comparison with zero
87  // (not just equality).  So there are some transformations that lose
88  // CC values (while still being worthwhile) and others that happen to make
89  // the CC result more useful than it was originally.
90  //
91  // Another reason is that we only want to use BRANCH ON COUNT in cases
92  // where we know that the count register is not going to be spilled.
93  //
94  // Doing it so late makes it more likely that a register will be reused
95  // between the comparison and the branch, but it isn't clear whether
96  // preventing that would be a win or not.
97  if (getOptLevel() != CodeGenOpt::None)
98    addPass(createSystemZElimComparePass(getSystemZTargetMachine()));
99  if (getOptLevel() != CodeGenOpt::None)
100    addPass(createSystemZShortenInstPass(getSystemZTargetMachine()));
101  addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
102  return true;
103}
104
105TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
106  return new SystemZPassConfig(this, PM);
107}
108