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 namespace {
35 /// SystemZ Code Generator Pass Configuration Options.
36 class SystemZPassConfig : public TargetPassConfig {
37 public:
38   SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
39     : TargetPassConfig(TM, PM) {}
40 
41   SystemZTargetMachine &getSystemZTargetMachine() const {
42     return getTM<SystemZTargetMachine>();
43   }
44 
45   void addIRPasses() override;
46   bool addInstSelector() override;
47   bool addPreSched2() override;
48   bool addPreEmitPass() override;
49 };
50 } // end anonymous namespace
51 
52 void SystemZPassConfig::addIRPasses() {
53   TargetPassConfig::addIRPasses();
54 }
55 
56 bool SystemZPassConfig::addInstSelector() {
57   addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
58   return false;
59 }
60 
61 bool SystemZPassConfig::addPreSched2() {
62   if (getOptLevel() != CodeGenOpt::None &&
63       getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
64     addPass(&IfConverterID);
65   return true;
66 }
67 
68 bool SystemZPassConfig::addPreEmitPass() {
69   // We eliminate comparisons here rather than earlier because some
70   // transformations can change the set of available CC values and we
71   // generally want those transformations to have priority.  This is
72   // especially true in the commonest case where the result of the comparison
73   // is used by a single in-range branch instruction, since we will then
74   // be able to fuse the compare and the branch instead.
75   //
76   // For example, two-address NILF can sometimes be converted into
77   // three-address RISBLG.  NILF produces a CC value that indicates whether
78   // the low word is zero, but RISBLG does not modify CC at all.  On the
79   // other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
80   // The CC value produced by NILL isn't useful for our purposes, but the
81   // value produced by RISBG can be used for any comparison with zero
82   // (not just equality).  So there are some transformations that lose
83   // CC values (while still being worthwhile) and others that happen to make
84   // the CC result more useful than it was originally.
85   //
86   // Another reason is that we only want to use BRANCH ON COUNT in cases
87   // where we know that the count register is not going to be spilled.
88   //
89   // Doing it so late makes it more likely that a register will be reused
90   // between the comparison and the branch, but it isn't clear whether
91   // preventing that would be a win or not.
92   if (getOptLevel() != CodeGenOpt::None)
93     addPass(createSystemZElimComparePass(getSystemZTargetMachine()));
94   if (getOptLevel() != CodeGenOpt::None)
95     addPass(createSystemZShortenInstPass(getSystemZTargetMachine()));
96   addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
97   return true;
98 }
99 
100 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
101   return new SystemZPassConfig(this, PM);
102 }
103