1 //===-- SystemZTargetMachine.cpp - Define TargetMachine for SystemZ -------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "SystemZTargetMachine.h"
11 #include "llvm/CodeGen/Passes.h"
12 #include "llvm/Support/TargetRegistry.h"
13 #include "llvm/Transforms/Scalar.h"
17 extern "C" void LLVMInitializeSystemZTarget() {
18 // Register the target.
19 RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
22 SystemZTargetMachine::SystemZTargetMachine(const Target &T, StringRef TT,
23 StringRef CPU, StringRef FS,
24 const TargetOptions &Options,
25 Reloc::Model RM, CodeModel::Model CM,
27 : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
28 Subtarget(TT, CPU, FS, *this) {
33 /// SystemZ Code Generator Pass Configuration Options.
34 class SystemZPassConfig : public TargetPassConfig {
36 SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
37 : TargetPassConfig(TM, PM) {}
39 SystemZTargetMachine &getSystemZTargetMachine() const {
40 return getTM<SystemZTargetMachine>();
43 void addIRPasses() override;
44 bool addInstSelector() override;
45 bool addPreSched2() override;
46 bool addPreEmitPass() override;
48 } // end anonymous namespace
50 void SystemZPassConfig::addIRPasses() {
51 TargetPassConfig::addIRPasses();
54 bool SystemZPassConfig::addInstSelector() {
55 addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
59 bool SystemZPassConfig::addPreSched2() {
60 if (getOptLevel() != CodeGenOpt::None &&
61 getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
62 addPass(&IfConverterID);
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.
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.
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.
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()));
98 TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
99 return new SystemZPassConfig(this, PM);