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