llvm-6502/lib/Target/ARM/ARMSubtarget.cpp
Evan Cheng 53519f015e Last round of fixes for movw + movt global address codegen.
1. Fixed ARM pc adjustment.
2. Fixed dynamic-no-pic codegen
3. CSE of pc-relative load of global addresses.

It's now enabled by default for Darwin.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123991 91177308-0d34-0410-b5e6-96231b3b80d8
2011-01-21 18:55:51 +00:00

253 lines
7.7 KiB
C++

//===-- ARMSubtarget.cpp - ARM Subtarget Information ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the ARM specific subclass of TargetSubtarget.
//
//===----------------------------------------------------------------------===//
#include "ARMSubtarget.h"
#include "ARMGenSubtarget.inc"
#include "ARMBaseRegisterInfo.h"
#include "llvm/GlobalValue.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/ADT/SmallVector.h"
using namespace llvm;
static cl::opt<bool>
ReserveR9("arm-reserve-r9", cl::Hidden,
cl::desc("Reserve R9, making it unavailable as GPR"));
static cl::opt<bool>
DarwinUseMOVT("arm-darwin-use-movt", cl::init(true), cl::Hidden);
static cl::opt<bool>
StrictAlign("arm-strict-align", cl::Hidden,
cl::desc("Disallow all unaligned memory accesses"));
ARMSubtarget::ARMSubtarget(const std::string &TT, const std::string &FS,
bool isT)
: ARMArchVersion(V4)
, ARMProcFamily(Others)
, ARMFPUType(None)
, UseNEONForSinglePrecisionFP(false)
, SlowFPVMLx(false)
, SlowFPBrcc(false)
, IsThumb(isT)
, ThumbMode(Thumb1)
, NoARM(false)
, PostRAScheduler(false)
, IsR9Reserved(ReserveR9)
, UseMovt(false)
, HasFP16(false)
, HasD16(false)
, HasHardwareDivide(false)
, HasT2ExtractPack(false)
, HasDataBarrier(false)
, Pref32BitThumb(false)
, HasMPExtension(false)
, FPOnlySP(false)
, AllowsUnalignedMem(false)
, stackAlignment(4)
, CPUString("generic")
, TargetTriple(TT)
, TargetABI(ARM_ABI_APCS) {
// Default to soft float ABI
if (FloatABIType == FloatABI::Default)
FloatABIType = FloatABI::Soft;
// Determine default and user specified characteristics
// When no arch is specified either by CPU or by attributes, make the default
// ARMv4T.
const char *ARMArchFeature = "";
if (CPUString == "generic" && (FS.empty() || FS == "generic")) {
ARMArchVersion = V4T;
ARMArchFeature = ",+v4t";
}
// Set the boolean corresponding to the current target triple, or the default
// if one cannot be determined, to true.
unsigned Len = TT.length();
unsigned Idx = 0;
if (Len >= 5 && TT.substr(0, 4) == "armv")
Idx = 4;
else if (Len >= 6 && TT.substr(0, 5) == "thumb") {
IsThumb = true;
if (Len >= 7 && TT[5] == 'v')
Idx = 6;
}
if (Idx) {
unsigned SubVer = TT[Idx];
if (SubVer >= '7' && SubVer <= '9') {
ARMArchVersion = V7A;
ARMArchFeature = ",+v7a";
if (Len >= Idx+2 && TT[Idx+1] == 'm') {
ARMArchVersion = V7M;
ARMArchFeature = ",+v7m";
}
} else if (SubVer == '6') {
ARMArchVersion = V6;
ARMArchFeature = ",+v6";
if (Len >= Idx+3 && TT[Idx+1] == 't' && TT[Idx+2] == '2') {
ARMArchVersion = V6T2;
ARMArchFeature = ",+v6t2";
}
} else if (SubVer == '5') {
ARMArchVersion = V5T;
ARMArchFeature = ",+v5t";
if (Len >= Idx+3 && TT[Idx+1] == 't' && TT[Idx+2] == 'e') {
ARMArchVersion = V5TE;
ARMArchFeature = ",+v5te";
}
} else if (SubVer == '4') {
if (Len >= Idx+2 && TT[Idx+1] == 't') {
ARMArchVersion = V4T;
ARMArchFeature = ",+v4t";
} else {
ARMArchVersion = V4;
ARMArchFeature = "";
}
}
}
if (TT.find("eabi") != std::string::npos)
TargetABI = ARM_ABI_AAPCS;
// Parse features string. If the first entry in FS (the CPU) is missing,
// insert the architecture feature derived from the target triple. This is
// important for setting features that are implied based on the architecture
// version.
std::string FSWithArch;
if (FS.empty())
FSWithArch = std::string(ARMArchFeature);
else if (FS.find(',') == 0)
FSWithArch = std::string(ARMArchFeature) + FS;
else
FSWithArch = FS;
CPUString = ParseSubtargetFeatures(FSWithArch, CPUString);
// After parsing Itineraries, set ItinData.IssueWidth.
computeIssueWidth();
// Thumb2 implies at least V6T2.
if (ARMArchVersion >= V6T2)
ThumbMode = Thumb2;
else if (ThumbMode >= Thumb2)
ARMArchVersion = V6T2;
if (isAAPCS_ABI())
stackAlignment = 8;
if (!isTargetDarwin())
UseMovt = hasV6T2Ops();
else {
IsR9Reserved = ReserveR9 | (ARMArchVersion < V6);
UseMovt = DarwinUseMOVT && hasV6T2Ops();
}
if (!isThumb() || hasThumb2())
PostRAScheduler = true;
// v6+ may or may not support unaligned mem access depending on the system
// configuration.
if (!StrictAlign && hasV6Ops() && isTargetDarwin())
AllowsUnalignedMem = true;
}
/// GVIsIndirectSymbol - true if the GV will be accessed via an indirect symbol.
bool
ARMSubtarget::GVIsIndirectSymbol(const GlobalValue *GV,
Reloc::Model RelocM) const {
if (RelocM == Reloc::Static)
return false;
// Materializable GVs (in JIT lazy compilation mode) do not require an extra
// load from stub.
bool isDecl = GV->isDeclaration() && !GV->isMaterializable();
if (!isTargetDarwin()) {
// Extra load is needed for all externally visible.
if (GV->hasLocalLinkage() || GV->hasHiddenVisibility())
return false;
return true;
} else {
if (RelocM == Reloc::PIC_) {
// If this is a strong reference to a definition, it is definitely not
// through a stub.
if (!isDecl && !GV->isWeakForLinker())
return false;
// Unless we have a symbol with hidden visibility, we have to go through a
// normal $non_lazy_ptr stub because this symbol might be resolved late.
if (!GV->hasHiddenVisibility()) // Non-hidden $non_lazy_ptr reference.
return true;
// If symbol visibility is hidden, we have a stub for common symbol
// references and external declarations.
if (isDecl || GV->hasCommonLinkage())
// Hidden $non_lazy_ptr reference.
return true;
return false;
} else {
// If this is a strong reference to a definition, it is definitely not
// through a stub.
if (!isDecl && !GV->isWeakForLinker())
return false;
// Unless we have a symbol with hidden visibility, we have to go through a
// normal $non_lazy_ptr stub because this symbol might be resolved late.
if (!GV->hasHiddenVisibility()) // Non-hidden $non_lazy_ptr reference.
return true;
}
}
return false;
}
unsigned ARMSubtarget::getMispredictionPenalty() const {
// If we have a reasonable estimate of the pipeline depth, then we can
// estimate the penalty of a misprediction based on that.
if (isCortexA8())
return 13;
else if (isCortexA9())
return 8;
// Otherwise, just return a sensible default.
return 10;
}
void ARMSubtarget::computeIssueWidth() {
unsigned allStage1Units = 0;
for (const InstrItinerary *itin = InstrItins.Itineraries;
itin->FirstStage != ~0U; ++itin) {
const InstrStage *IS = InstrItins.Stages + itin->FirstStage;
allStage1Units |= IS->getUnits();
}
InstrItins.IssueWidth = 0;
while (allStage1Units) {
++InstrItins.IssueWidth;
// clear the lowest bit
allStage1Units ^= allStage1Units & ~(allStage1Units - 1);
}
assert(InstrItins.IssueWidth <= 2 && "itinerary bug, too many stage 1 units");
}
bool ARMSubtarget::enablePostRAScheduler(
CodeGenOpt::Level OptLevel,
TargetSubtarget::AntiDepBreakMode& Mode,
RegClassVector& CriticalPathRCs) const {
Mode = TargetSubtarget::ANTIDEP_CRITICAL;
CriticalPathRCs.clear();
CriticalPathRCs.push_back(&ARM::GPRRegClass);
return PostRAScheduler && OptLevel >= CodeGenOpt::Default;
}