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   bool addPreSched2() override;
50   bool 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 bool SystemZPassConfig::addPreSched2() {
64   if (getOptLevel() != CodeGenOpt::None &&
65       getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
66     addPass(&IfConverterID);
67   return true;
68 }
69 
70 bool SystemZPassConfig::addPreEmitPass() {
71   // We eliminate comparisons here rather than earlier because some
72   // transformations can change the set of available CC values and we
73   // generally want those transformations to have priority.  This is
74   // especially true in the commonest case where the result of the comparison
75   // is used by a single in-range branch instruction, since we will then
76   // be able to fuse the compare and the branch instead.
77   //
78   // For example, two-address NILF can sometimes be converted into
79   // three-address RISBLG.  NILF produces a CC value that indicates whether
80   // the low word is zero, but RISBLG does not modify CC at all.  On the
81   // other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
82   // The CC value produced by NILL isn't useful for our purposes, but the
83   // value produced by RISBG can be used for any comparison with zero
84   // (not just equality).  So there are some transformations that lose
85   // CC values (while still being worthwhile) and others that happen to make
86   // the CC result more useful than it was originally.
87   //
88   // Another reason is that we only want to use BRANCH ON COUNT in cases
89   // where we know that the count register is not going to be spilled.
90   //
91   // Doing it so late makes it more likely that a register will be reused
92   // between the comparison and the branch, but it isn't clear whether
93   // preventing that would be a win or not.
94   if (getOptLevel() != CodeGenOpt::None)
95     addPass(createSystemZElimComparePass(getSystemZTargetMachine()));
96   if (getOptLevel() != CodeGenOpt::None)
97     addPass(createSystemZShortenInstPass(getSystemZTargetMachine()));
98   addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
99   return true;
100 }
101 
102 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
103   return new SystemZPassConfig(this, PM);
104 }
105