src/llvm/lib/Target/SystemZ/SystemZTargetMachine.cpp

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