SystemZTargetMachine.cpp revision 66fbb4781841a8411a772b6909a7e0de182b896f 
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
14using namespace llvm;
15
16extern "C" void LLVMInitializeSystemZTarget() {
17  // Register the target.
18  RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
19}
20
21SystemZTargetMachine::SystemZTargetMachine(const Target &T, StringRef TT,
22                                           StringRef CPU, StringRef FS,
23                                           const TargetOptions &Options,
24                                           Reloc::Model RM,
25                                           CodeModel::Model CM,
26                                           CodeGenOpt::Level OL)
27  : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
28    Subtarget(TT, CPU, FS),
29    // Make sure that global data has at least 16 bits of alignment by default,
30    // so that we can refer to it using LARL.  We don't have any special
31    // requirements for stack variables though.
32    DL("E-p:64:64:64-i1:8:16-i8:8:16-i16:16-i32:32-i64:64"
33       "-f32:32-f64:64-f128:64-a0:8:16-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  virtual bool addInstSelector() LLVM_OVERRIDE;
51  virtual bool addPreSched2() LLVM_OVERRIDE;
52  virtual bool addPreEmitPass() LLVM_OVERRIDE;
53};
54} // end anonymous namespace
55
56bool SystemZPassConfig::addInstSelector() {
57  addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
58  return false;
59}
60
61bool SystemZPassConfig::addPreSched2() {
62  if (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  // Doing it so late makes it more likely that a register will be reused
86  // between the comparison and the branch, but it isn't clear whether
87  // preventing that would be a win or not.
88  if (getOptLevel() != CodeGenOpt::None)
89    addPass(createSystemZElimComparePass(getSystemZTargetMachine()));
90  addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
91  return true;
92}
93
94TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
95  return new SystemZPassConfig(this, PM);
96}
97