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       // Make sure that global data has at least 16 bits of alignment by
31       // default, so that we can refer to it using LARL.  We don't have any
32       // special 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       Subtarget(TT, CPU, FS, *this) {
35   initAsmInfo();
36 }
37 
38 SystemZTargetMachine::~SystemZTargetMachine() {}
39 
40 namespace {
41 /// SystemZ Code Generator Pass Configuration Options.
42 class SystemZPassConfig : public TargetPassConfig {
43 public:
44   SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
45     : TargetPassConfig(TM, PM) {}
46 
47   SystemZTargetMachine &getSystemZTargetMachine() const {
48     return getTM<SystemZTargetMachine>();
49   }
50 
51   void addIRPasses() override;
52   bool addInstSelector() override;
53   void addPreSched2() override;
54   void addPreEmitPass() override;
55 };
56 } // end anonymous namespace
57 
58 void SystemZPassConfig::addIRPasses() {
59   TargetPassConfig::addIRPasses();
60 }
61 
62 bool SystemZPassConfig::addInstSelector() {
63   addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
64   return false;
65 }
66 
67 void SystemZPassConfig::addPreSched2() {
68   if (getOptLevel() != CodeGenOpt::None &&
69       getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
70     addPass(&IfConverterID);
71 }
72 
73 void 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()), false);
99   if (getOptLevel() != CodeGenOpt::None)
100     addPass(createSystemZShortenInstPass(getSystemZTargetMachine()), false);
101   addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
102 }
103 
104 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
105   return new SystemZPassConfig(this, PM);
106 }
107