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This adds a scheduling model for the POWER7 (P7) core, and enables the machine-instruction scheduler when targeting the P7. Scheduling for the P7, like earlier ooo PPC cores, requires considering both dispatch group hazards, and functional unit resources and latencies. These are both modeled in a combined itinerary. Dispatch group formation is still handled by the post-RA scheduler (which still needs to be updated for the P7, but nevertheless does a pretty good job). One interesting aspect of this change is that I've also enabled to use of AA duing CodeGen for the P7 (just as it is for the embedded cores). The benchmark results seem to support this decision (see below), and while this is normally useful for in-order cores, and not for ooo cores like the P7, I think that the dispatch slot hazards are enough like in-order resources to make the AA useful. Test suite significant performance differences (where negative is a speedup, and positive is a regression) vs. the current situation: MultiSource/Benchmarks/BitBench/drop3/drop3 with AA: N/A without AA: -28.7614% +/- 19.8356% (significantly against AA) MultiSource/Benchmarks/FreeBench/neural/neural with AA: -17.7406% +/- 11.2712% without AA: N/A (significantly in favor of AA) MultiSource/Benchmarks/SciMark2-C/scimark2 with AA: -11.2079% +/- 1.80543% without AA: -11.3263% +/- 2.79651% MultiSource/Benchmarks/TSVC/Symbolics-flt/Symbolics-flt with AA: -41.8649% +/- 17.0053% without AA: -34.5256% +/- 23.7072% MultiSource/Benchmarks/mafft/pairlocalalign with AA: 25.3016% +/- 17.8614% without AA: 38.6629% +/- 14.9391% (significantly in favor of AA) MultiSource/Benchmarks/sim/sim with AA: N/A without AA: 13.4844% +/- 7.18195% (significantly in favor of AA) SingleSource/Benchmarks/BenchmarkGame/Large/fasta with AA: 15.0664% +/- 6.70216% without AA: 12.7747% +/- 8.43043% SingleSource/Benchmarks/BenchmarkGame/puzzle with AA: 82.2713% +/- 26.3567% without AA: 75.7525% +/- 41.1842% SingleSource/Benchmarks/Misc/flops-2 with AA: -37.1621% +/- 20.7964% without AA: -35.2342% +/- 20.2999% (significantly in favor of AA) These are 99.5% confidence intervals from 5 runs per configuration. Regarding the choice to turn on AA during CodeGen, of these results, four seem significantly in favor of using AA, and one seems significantly against. I'm not making this decision based on these numbers alone, but these results seem consistent with results I have from other tests, and so I think that, on balance, using AA is a win. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195981 91177308-0d34-0410-b5e6-96231b3b80d8
221 lines
7.0 KiB
C++
221 lines
7.0 KiB
C++
//===-- PowerPCSubtarget.cpp - PPC Subtarget Information ------------------===//
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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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//
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// This file implements the PPC specific subclass of TargetSubtargetInfo.
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//
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//===----------------------------------------------------------------------===//
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#include "PPCSubtarget.h"
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#include "PPC.h"
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#include "PPCRegisterInfo.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineScheduler.h"
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#include "llvm/IR/Attributes.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/IR/Function.h"
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#include "llvm/Support/Host.h"
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#include "llvm/Support/TargetRegistry.h"
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#include "llvm/Target/TargetMachine.h"
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#include <cstdlib>
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#define GET_SUBTARGETINFO_TARGET_DESC
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#define GET_SUBTARGETINFO_CTOR
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#include "PPCGenSubtargetInfo.inc"
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using namespace llvm;
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PPCSubtarget::PPCSubtarget(const std::string &TT, const std::string &CPU,
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const std::string &FS, bool is64Bit)
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: PPCGenSubtargetInfo(TT, CPU, FS)
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, IsPPC64(is64Bit)
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, TargetTriple(TT) {
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initializeEnvironment();
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resetSubtargetFeatures(CPU, FS);
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}
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/// SetJITMode - This is called to inform the subtarget info that we are
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/// producing code for the JIT.
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void PPCSubtarget::SetJITMode() {
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// JIT mode doesn't want lazy resolver stubs, it knows exactly where
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// everything is. This matters for PPC64, which codegens in PIC mode without
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// stubs.
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HasLazyResolverStubs = false;
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// Calls to external functions need to use indirect calls
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IsJITCodeModel = true;
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}
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void PPCSubtarget::resetSubtargetFeatures(const MachineFunction *MF) {
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AttributeSet FnAttrs = MF->getFunction()->getAttributes();
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Attribute CPUAttr = FnAttrs.getAttribute(AttributeSet::FunctionIndex,
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"target-cpu");
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Attribute FSAttr = FnAttrs.getAttribute(AttributeSet::FunctionIndex,
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"target-features");
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std::string CPU =
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!CPUAttr.hasAttribute(Attribute::None) ? CPUAttr.getValueAsString() : "";
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std::string FS =
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!FSAttr.hasAttribute(Attribute::None) ? FSAttr.getValueAsString() : "";
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if (!FS.empty()) {
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initializeEnvironment();
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resetSubtargetFeatures(CPU, FS);
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}
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}
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void PPCSubtarget::initializeEnvironment() {
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StackAlignment = 16;
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DarwinDirective = PPC::DIR_NONE;
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HasMFOCRF = false;
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Has64BitSupport = false;
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Use64BitRegs = false;
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HasAltivec = false;
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HasQPX = false;
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HasFCPSGN = false;
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HasFSQRT = false;
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HasFRE = false;
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HasFRES = false;
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HasFRSQRTE = false;
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HasFRSQRTES = false;
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HasRecipPrec = false;
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HasSTFIWX = false;
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HasLFIWAX = false;
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HasFPRND = false;
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HasFPCVT = false;
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HasISEL = false;
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HasPOPCNTD = false;
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HasLDBRX = false;
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IsBookE = false;
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DeprecatedMFTB = false;
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DeprecatedDST = false;
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HasLazyResolverStubs = false;
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IsJITCodeModel = false;
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}
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void PPCSubtarget::resetSubtargetFeatures(StringRef CPU, StringRef FS) {
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// Determine default and user specified characteristics
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std::string CPUName = CPU;
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if (CPUName.empty())
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CPUName = "generic";
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#if (defined(__APPLE__) || defined(__linux__)) && \
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(defined(__ppc__) || defined(__powerpc__))
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if (CPUName == "generic")
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CPUName = sys::getHostCPUName();
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#endif
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// Initialize scheduling itinerary for the specified CPU.
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InstrItins = getInstrItineraryForCPU(CPUName);
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// Make sure 64-bit features are available when CPUname is generic
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std::string FullFS = FS;
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// If we are generating code for ppc64, verify that options make sense.
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if (IsPPC64) {
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Has64BitSupport = true;
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// Silently force 64-bit register use on ppc64.
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Use64BitRegs = true;
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if (!FullFS.empty())
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FullFS = "+64bit," + FullFS;
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else
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FullFS = "+64bit";
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}
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// Parse features string.
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ParseSubtargetFeatures(CPUName, FullFS);
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// If the user requested use of 64-bit regs, but the cpu selected doesn't
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// support it, ignore.
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if (use64BitRegs() && !has64BitSupport())
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Use64BitRegs = false;
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// Set up darwin-specific properties.
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if (isDarwin())
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HasLazyResolverStubs = true;
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// QPX requires a 32-byte aligned stack. Note that we need to do this if
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// we're compiling for a BG/Q system regardless of whether or not QPX
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// is enabled because external functions will assume this alignment.
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if (hasQPX() || isBGQ())
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StackAlignment = 32;
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// Determine endianness.
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IsLittleEndian = (TargetTriple.getArch() == Triple::ppc64le);
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}
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/// hasLazyResolverStub - Return true if accesses to the specified global have
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/// to go through a dyld lazy resolution stub. This means that an extra load
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/// is required to get the address of the global.
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bool PPCSubtarget::hasLazyResolverStub(const GlobalValue *GV,
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const TargetMachine &TM) const {
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// We never have stubs if HasLazyResolverStubs=false or if in static mode.
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if (!HasLazyResolverStubs || TM.getRelocationModel() == Reloc::Static)
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return false;
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// If symbol visibility is hidden, the extra load is not needed if
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// the symbol is definitely defined in the current translation unit.
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bool isDecl = GV->isDeclaration() && !GV->isMaterializable();
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if (GV->hasHiddenVisibility() && !isDecl && !GV->hasCommonLinkage())
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return false;
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return GV->hasWeakLinkage() || GV->hasLinkOnceLinkage() ||
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GV->hasCommonLinkage() || isDecl;
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}
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bool PPCSubtarget::enablePostRAScheduler(
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CodeGenOpt::Level OptLevel,
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TargetSubtargetInfo::AntiDepBreakMode& Mode,
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RegClassVector& CriticalPathRCs) const {
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Mode = TargetSubtargetInfo::ANTIDEP_ALL;
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CriticalPathRCs.clear();
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if (isPPC64())
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CriticalPathRCs.push_back(&PPC::G8RCRegClass);
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else
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CriticalPathRCs.push_back(&PPC::GPRCRegClass);
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return OptLevel >= CodeGenOpt::Default;
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}
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// Embedded cores need aggressive scheduling (and some others also benefit).
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static bool needsAggressiveScheduling(unsigned Directive) {
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switch (Directive) {
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default: return false;
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case PPC::DIR_440:
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case PPC::DIR_A2:
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case PPC::DIR_E500mc:
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case PPC::DIR_E5500:
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case PPC::DIR_PWR7:
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return true;
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}
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}
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bool PPCSubtarget::enableMachineScheduler() const {
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// Enable MI scheduling for the embedded cores.
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// FIXME: Enable this for all cores (some additional modeling
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// may be necessary).
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return needsAggressiveScheduling(DarwinDirective);
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}
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void PPCSubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
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MachineInstr *begin,
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MachineInstr *end,
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unsigned NumRegionInstrs) const {
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if (needsAggressiveScheduling(DarwinDirective)) {
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Policy.OnlyTopDown = false;
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Policy.OnlyBottomUp = false;
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}
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// Spilling is generally expensive on all PPC cores, so always enable
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// register-pressure tracking.
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Policy.ShouldTrackPressure = true;
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}
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bool PPCSubtarget::useAA() const {
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// Use AA during code generation for the embedded cores.
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return needsAggressiveScheduling(DarwinDirective);
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}
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