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9379557478
This patch just uses a peephole test for "add; compare; branch" sequences within a single block. The IR optimizers already convert loops to decrement-and-branch-on-nonzero form in some cases, so even this simplistic test triggers many times during a clang bootstrap and projects/test-suite run. It looks like there are still cases where we need to more strongly prefer branches on nonzero though. E.g. I saw a case where a loop that started out with a check for 0 ended up with a check for -1. I'll try to look at that sometime. I ended up adding the Reference class because MachineInstr::readsRegister() doesn't check for subregisters (by design, as far as I could tell). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187723 91177308-0d34-0410-b5e6-96231b3b80d8
100 lines
4.0 KiB
C++
100 lines
4.0 KiB
C++
//===-- SystemZTargetMachine.cpp - Define TargetMachine for SystemZ -------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "SystemZTargetMachine.h"
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#include "llvm/CodeGen/Passes.h"
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#include "llvm/Support/TargetRegistry.h"
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using namespace llvm;
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extern "C" void LLVMInitializeSystemZTarget() {
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// Register the target.
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RegisterTargetMachine<SystemZTargetMachine> X(TheSystemZTarget);
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}
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SystemZTargetMachine::SystemZTargetMachine(const Target &T, StringRef TT,
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StringRef CPU, StringRef FS,
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const TargetOptions &Options,
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Reloc::Model RM,
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CodeModel::Model CM,
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CodeGenOpt::Level OL)
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: LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
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Subtarget(TT, CPU, FS),
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// Make sure that global data has at least 16 bits of alignment by default,
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// so that we can refer to it using LARL. We don't have any special
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// requirements for stack variables though.
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DL("E-p:64:64:64-i1:8:16-i8:8:16-i16:16-i32:32-i64:64"
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"-f32:32-f64:64-f128:64-a0:8:16-n32:64"),
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InstrInfo(*this), TLInfo(*this), TSInfo(*this),
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FrameLowering(*this, Subtarget) {
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initAsmInfo();
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}
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namespace {
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/// SystemZ Code Generator Pass Configuration Options.
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class SystemZPassConfig : public TargetPassConfig {
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public:
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SystemZPassConfig(SystemZTargetMachine *TM, PassManagerBase &PM)
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: TargetPassConfig(TM, PM) {}
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SystemZTargetMachine &getSystemZTargetMachine() const {
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return getTM<SystemZTargetMachine>();
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}
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virtual bool addInstSelector() LLVM_OVERRIDE;
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virtual bool addPreSched2() LLVM_OVERRIDE;
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virtual bool addPreEmitPass() LLVM_OVERRIDE;
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};
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} // end anonymous namespace
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bool SystemZPassConfig::addInstSelector() {
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addPass(createSystemZISelDag(getSystemZTargetMachine(), getOptLevel()));
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return false;
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}
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bool SystemZPassConfig::addPreSched2() {
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if (getSystemZTargetMachine().getSubtargetImpl()->hasLoadStoreOnCond())
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addPass(&IfConverterID);
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return true;
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}
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bool SystemZPassConfig::addPreEmitPass() {
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// We eliminate comparisons here rather than earlier because some
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// transformations can change the set of available CC values and we
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// generally want those transformations to have priority. This is
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// especially true in the commonest case where the result of the comparison
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// is used by a single in-range branch instruction, since we will then
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// be able to fuse the compare and the branch instead.
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//
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// For example, two-address NILF can sometimes be converted into
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// three-address RISBLG. NILF produces a CC value that indicates whether
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// the low word is zero, but RISBLG does not modify CC at all. On the
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// other hand, 64-bit ANDs like NILL can sometimes be converted to RISBG.
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// The CC value produced by NILL isn't useful for our purposes, but the
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// value produced by RISBG can be used for any comparison with zero
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// (not just equality). So there are some transformations that lose
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// CC values (while still being worthwhile) and others that happen to make
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// the CC result more useful than it was originally.
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//
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// Another reason is that we only want to use BRANCH ON COUNT in cases
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// where we know that the count register is not going to be spilled.
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//
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// Doing it so late makes it more likely that a register will be reused
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// between the comparison and the branch, but it isn't clear whether
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// preventing that would be a win or not.
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if (getOptLevel() != CodeGenOpt::None)
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addPass(createSystemZElimComparePass(getSystemZTargetMachine()));
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addPass(createSystemZLongBranchPass(getSystemZTargetMachine()));
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return true;
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}
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TargetPassConfig *SystemZTargetMachine::createPassConfig(PassManagerBase &PM) {
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return new SystemZPassConfig(this, PM);
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}
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