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      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 
     15 using namespace llvm;
     16 
     17 extern "C" void LLVMInitializeSystemZTarget() {
     18   // Register the target.
     19   RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
     20 }
     21 
     22 SystemZTargetMachine::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 
     32 namespace {
     33 /// SystemZ Code Generator Pass Configuration Options.
     34 class SystemZPassConfig : public TargetPassConfig {
     35 public:
     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 
     50 void SystemZPassConfig::addIRPasses() {
     51   TargetPassConfig::addIRPasses();
     52   addPass(createPartiallyInlineLibCallsPass());
     53 }
     54 
     55 bool SystemZPassConfig::addInstSelector() {
     56   addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
     57   return false;
     58 }
     59 
     60 bool SystemZPassConfig::addPreSched2() {
     61   if (getOptLevel() != CodeGenOpt::None &&
     62       getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
     63     addPass(&IfConverterID);
     64   return true;
     65 }
     66 
     67 bool 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 
     99 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
    100   return new SystemZPassConfig(this, PM);
    101 }
    102