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llvm-6502/lib/Target/X86/X86Subtarget.cpp
Preston Gurd 2e2efd9600 Generic Bypass Slow Div 
- CodeGenPrepare pass for identifying div/rem ops
- Backend specifies the type mapping using addBypassSlowDivType
- Enabled only for Intel Atom with O2 32-bit -> 8-bit
- Replace IDIV with instructions which test its value and use DIVB if the value
is positive and less than 256.
- In the case when the quotient and remainder of a divide are used a DIV
and a REM instruction will be present in the IR. In the non-Atom case
they are both lowered to IDIVs and CSE removes the redundant IDIV instruction,
using the quotient and remainder from the first IDIV. However,
due to this optimization CSE is not able to eliminate redundant
IDIV instructions because they are located in different basic blocks.
This is overcome by calculating both the quotient (DIV) and remainder (REM)
in each basic block that is inserted by the optimization and reusing the result
values when a subsequent DIV or REM instruction uses the same operands.
- Test cases check for the presents of the optimization when calculating
either the quotient, remainder,  or both.

Patch by Tyler Nowicki!



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163150 91177308-0d34-0410-b5e6-96231b3b80d8
2012-09-04 18:22:17 +00:00

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14 KiB
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//===-- X86Subtarget.cpp - X86 Subtarget Information ----------------------===//
//
// 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 X86 specific subclass of TargetSubtargetInfo.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "subtarget"
#include "X86Subtarget.h"
#include "X86InstrInfo.h"
#include "llvm/GlobalValue.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Host.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#define GET_SUBTARGETINFO_TARGET_DESC
#define GET_SUBTARGETINFO_CTOR
#include "X86GenSubtargetInfo.inc"
using namespace llvm;
#if defined(_MSC_VER)
#include <intrin.h>
#endif
/// ClassifyBlockAddressReference - Classify a blockaddress reference for the
/// current subtarget according to how we should reference it in a non-pcrel
/// context.
unsigned char X86Subtarget::
ClassifyBlockAddressReference() const {
if (isPICStyleGOT()) // 32-bit ELF targets.
return X86II::MO_GOTOFF;
if (isPICStyleStubPIC()) // Darwin/32 in PIC mode.
return X86II::MO_PIC_BASE_OFFSET;
// Direct static reference to label.
return X86II::MO_NO_FLAG;
}
/// ClassifyGlobalReference - Classify a global variable reference for the
/// current subtarget according to how we should reference it in a non-pcrel
/// context.
unsigned char X86Subtarget::
ClassifyGlobalReference(const GlobalValue *GV, const TargetMachine &TM) const {
// DLLImport only exists on windows, it is implemented as a load from a
// DLLIMPORT stub.
if (GV->hasDLLImportLinkage())
return X86II::MO_DLLIMPORT;
// Determine whether this is a reference to a definition or a declaration.
// Materializable GVs (in JIT lazy compilation mode) do not require an extra
// load from stub.
bool isDecl = GV->hasAvailableExternallyLinkage();
if (GV->isDeclaration() && !GV->isMaterializable())
isDecl = true;
// X86-64 in PIC mode.
if (isPICStyleRIPRel()) {
// Large model never uses stubs.
if (TM.getCodeModel() == CodeModel::Large)
return X86II::MO_NO_FLAG;
if (isTargetDarwin()) {
// If symbol visibility is hidden, the extra load is not needed if
// target is x86-64 or the symbol is definitely defined in the current
// translation unit.
if (GV->hasDefaultVisibility() &&
(isDecl || GV->isWeakForLinker()))
return X86II::MO_GOTPCREL;
} else if (!isTargetWin64()) {
assert(isTargetELF() && "Unknown rip-relative target");
// Extra load is needed for all externally visible.
if (!GV->hasLocalLinkage() && GV->hasDefaultVisibility())
return X86II::MO_GOTPCREL;
}
return X86II::MO_NO_FLAG;
}
if (isPICStyleGOT()) { // 32-bit ELF targets.
// Extra load is needed for all externally visible.
if (GV->hasLocalLinkage() || GV->hasHiddenVisibility())
return X86II::MO_GOTOFF;
return X86II::MO_GOT;
}
if (isPICStyleStubPIC()) { // Darwin/32 in PIC mode.
// Determine whether we have a stub reference and/or whether the reference
// is relative to the PIC base or not.
// If this is a strong reference to a definition, it is definitely not
// through a stub.
if (!isDecl && !GV->isWeakForLinker())
return X86II::MO_PIC_BASE_OFFSET;
// 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 X86II::MO_DARWIN_NONLAZY_PIC_BASE;
// 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 X86II::MO_DARWIN_HIDDEN_NONLAZY_PIC_BASE;
}
// Otherwise, no stub.
return X86II::MO_PIC_BASE_OFFSET;
}
if (isPICStyleStubNoDynamic()) { // Darwin/32 in -mdynamic-no-pic mode.
// Determine whether we have a stub reference.
// If this is a strong reference to a definition, it is definitely not
// through a stub.
if (!isDecl && !GV->isWeakForLinker())
return X86II::MO_NO_FLAG;
// 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 X86II::MO_DARWIN_NONLAZY;
// Otherwise, no stub.
return X86II::MO_NO_FLAG;
}
// Direct static reference to global.
return X86II::MO_NO_FLAG;
}
/// getBZeroEntry - This function returns the name of a function which has an
/// interface like the non-standard bzero function, if such a function exists on
/// the current subtarget and it is considered prefereable over memset with zero
/// passed as the second argument. Otherwise it returns null.
const char *X86Subtarget::getBZeroEntry() const {
// Darwin 10 has a __bzero entry point for this purpose.
if (getTargetTriple().isMacOSX() &&
!getTargetTriple().isMacOSXVersionLT(10, 6))
return "__bzero";
return 0;
}
/// IsLegalToCallImmediateAddr - Return true if the subtarget allows calls
/// to immediate address.
bool X86Subtarget::IsLegalToCallImmediateAddr(const TargetMachine &TM) const {
if (In64BitMode)
return false;
return isTargetELF() || TM.getRelocationModel() == Reloc::Static;
}
/// getSpecialAddressLatency - For targets where it is beneficial to
/// backschedule instructions that compute addresses, return a value
/// indicating the number of scheduling cycles of backscheduling that
/// should be attempted.
unsigned X86Subtarget::getSpecialAddressLatency() const {
// For x86 out-of-order targets, back-schedule address computations so
// that loads and stores aren't blocked.
// This value was chosen arbitrarily.
return 200;
}
void X86Subtarget::AutoDetectSubtargetFeatures() {
unsigned EAX = 0, EBX = 0, ECX = 0, EDX = 0;
unsigned MaxLevel;
union {
unsigned u[3];
char c[12];
} text;
if (X86_MC::GetCpuIDAndInfo(0, &MaxLevel, text.u+0, text.u+2, text.u+1) ||
MaxLevel < 1)
return;
X86_MC::GetCpuIDAndInfo(0x1, &EAX, &EBX, &ECX, &EDX);
if ((EDX >> 15) & 1) { HasCMov = true; ToggleFeature(X86::FeatureCMOV); }
if ((EDX >> 23) & 1) { X86SSELevel = MMX; ToggleFeature(X86::FeatureMMX); }
if ((EDX >> 25) & 1) { X86SSELevel = SSE1; ToggleFeature(X86::FeatureSSE1); }
if ((EDX >> 26) & 1) { X86SSELevel = SSE2; ToggleFeature(X86::FeatureSSE2); }
if (ECX & 0x1) { X86SSELevel = SSE3; ToggleFeature(X86::FeatureSSE3); }
if ((ECX >> 9) & 1) { X86SSELevel = SSSE3; ToggleFeature(X86::FeatureSSSE3);}
if ((ECX >> 19) & 1) { X86SSELevel = SSE41; ToggleFeature(X86::FeatureSSE41);}
if ((ECX >> 20) & 1) { X86SSELevel = SSE42; ToggleFeature(X86::FeatureSSE42);}
if ((ECX >> 28) & 1) { X86SSELevel = AVX; ToggleFeature(X86::FeatureAVX); }
bool IsIntel = memcmp(text.c, "GenuineIntel", 12) == 0;
bool IsAMD = !IsIntel && memcmp(text.c, "AuthenticAMD", 12) == 0;
if ((ECX >> 1) & 0x1) {
HasPCLMUL = true;
ToggleFeature(X86::FeaturePCLMUL);
}
if ((ECX >> 12) & 0x1) {
HasFMA = true;
ToggleFeature(X86::FeatureFMA);
}
if (IsIntel && ((ECX >> 22) & 0x1)) {
HasMOVBE = true;
ToggleFeature(X86::FeatureMOVBE);
}
if ((ECX >> 23) & 0x1) {
HasPOPCNT = true;
ToggleFeature(X86::FeaturePOPCNT);
}
if ((ECX >> 25) & 0x1) {
HasAES = true;
ToggleFeature(X86::FeatureAES);
}
if ((ECX >> 29) & 0x1) {
HasF16C = true;
ToggleFeature(X86::FeatureF16C);
}
if (IsIntel && ((ECX >> 30) & 0x1)) {
HasRDRAND = true;
ToggleFeature(X86::FeatureRDRAND);
}
if ((ECX >> 13) & 0x1) {
HasCmpxchg16b = true;
ToggleFeature(X86::FeatureCMPXCHG16B);
}
if (IsIntel || IsAMD) {
// Determine if bit test memory instructions are slow.
unsigned Family = 0;
unsigned Model = 0;
X86_MC::DetectFamilyModel(EAX, Family, Model);
if (IsAMD || (Family == 6 && Model >= 13)) {
IsBTMemSlow = true;
ToggleFeature(X86::FeatureSlowBTMem);
}
// If it's Nehalem, unaligned memory access is fast.
// Include Westmere and Sandy Bridge as well.
// FIXME: add later processors.
if (IsIntel && ((Family == 6 && Model == 26) ||
(Family == 6 && Model == 44) ||
(Family == 6 && Model == 42))) {
IsUAMemFast = true;
ToggleFeature(X86::FeatureFastUAMem);
}
// Set processor type. Currently only Atom is detected.
if (Family == 6 &&
(Model == 28 || Model == 38 || Model == 39
|| Model == 53 || Model == 54)) {
X86ProcFamily = IntelAtom;
UseLeaForSP = true;
ToggleFeature(X86::FeatureLeaForSP);
}
unsigned MaxExtLevel;
X86_MC::GetCpuIDAndInfo(0x80000000, &MaxExtLevel, &EBX, &ECX, &EDX);
if (MaxExtLevel >= 0x80000001) {
X86_MC::GetCpuIDAndInfo(0x80000001, &EAX, &EBX, &ECX, &EDX);
if ((EDX >> 29) & 0x1) {
HasX86_64 = true;
ToggleFeature(X86::Feature64Bit);
}
if ((ECX >> 5) & 0x1) {
HasLZCNT = true;
ToggleFeature(X86::FeatureLZCNT);
}
if (IsAMD) {
if ((ECX >> 6) & 0x1) {
HasSSE4A = true;
ToggleFeature(X86::FeatureSSE4A);
}
if ((ECX >> 11) & 0x1) {
HasXOP = true;
ToggleFeature(X86::FeatureXOP);
}
if ((ECX >> 16) & 0x1) {
HasFMA4 = true;
ToggleFeature(X86::FeatureFMA4);
}
}
}
}
if (MaxLevel >= 7) {
if (!X86_MC::GetCpuIDAndInfoEx(0x7, 0x0, &EAX, &EBX, &ECX, &EDX)) {
if (IsIntel && (EBX & 0x1)) {
HasFSGSBase = true;
ToggleFeature(X86::FeatureFSGSBase);
}
if ((EBX >> 3) & 0x1) {
HasBMI = true;
ToggleFeature(X86::FeatureBMI);
}
if (IsIntel && ((EBX >> 5) & 0x1)) {
X86SSELevel = AVX2;
ToggleFeature(X86::FeatureAVX2);
}
if (IsIntel && ((EBX >> 8) & 0x1)) {
HasBMI2 = true;
ToggleFeature(X86::FeatureBMI2);
}
}
}
}
X86Subtarget::X86Subtarget(const std::string &TT, const std::string &CPU,
const std::string &FS,
unsigned StackAlignOverride, bool is64Bit)
: X86GenSubtargetInfo(TT, CPU, FS)
, X86ProcFamily(Others)
, PICStyle(PICStyles::None)
, X86SSELevel(NoMMXSSE)
, X863DNowLevel(NoThreeDNow)
, HasCMov(false)
, HasX86_64(false)
, HasPOPCNT(false)
, HasSSE4A(false)
, HasAES(false)
, HasPCLMUL(false)
, HasFMA(false)
, HasFMA4(false)
, HasXOP(false)
, HasMOVBE(false)
, HasRDRAND(false)
, HasF16C(false)
, HasFSGSBase(false)
, HasLZCNT(false)
, HasBMI(false)
, HasBMI2(false)
, IsBTMemSlow(false)
, IsUAMemFast(false)
, HasVectorUAMem(false)
, HasCmpxchg16b(false)
, UseLeaForSP(false)
, HasSlowDivide(false)
, PostRAScheduler(false)
, stackAlignment(4)
// FIXME: this is a known good value for Yonah. How about others?
, MaxInlineSizeThreshold(128)
, TargetTriple(TT)
, In64BitMode(is64Bit) {
// Determine default and user specified characteristics
std::string CPUName = CPU;
if (!FS.empty() || !CPU.empty()) {
if (CPUName.empty()) {
#if defined(i386) || defined(__i386__) || defined(__x86__) || defined(_M_IX86)\
|| defined(__x86_64__) || defined(_M_AMD64) || defined (_M_X64)
CPUName = sys::getHostCPUName();
#else
CPUName = "generic";
#endif
}
// Make sure 64-bit features are available in 64-bit mode. (But make sure
// SSE2 can be turned off explicitly.)
std::string FullFS = FS;
if (In64BitMode) {
if (!FullFS.empty())
FullFS = "+64bit,+sse2," + FullFS;
else
FullFS = "+64bit,+sse2";
}
// If feature string is not empty, parse features string.
ParseSubtargetFeatures(CPUName, FullFS);
} else {
if (CPUName.empty()) {
#if defined (__x86_64__) || defined(__i386__)
CPUName = sys::getHostCPUName();
#else
CPUName = "generic";
#endif
}
// Otherwise, use CPUID to auto-detect feature set.
AutoDetectSubtargetFeatures();
// Make sure 64-bit features are available in 64-bit mode.
if (In64BitMode) {
HasX86_64 = true; ToggleFeature(X86::Feature64Bit);
HasCMov = true; ToggleFeature(X86::FeatureCMOV);
if (X86SSELevel < SSE2) {
X86SSELevel = SSE2;
ToggleFeature(X86::FeatureSSE1);
ToggleFeature(X86::FeatureSSE2);
}
}
}
if (X86ProcFamily == IntelAtom)
PostRAScheduler = true;
InstrItins = getInstrItineraryForCPU(CPUName);
// It's important to keep the MCSubtargetInfo feature bits in sync with
// target data structure which is shared with MC code emitter, etc.
if (In64BitMode)
ToggleFeature(X86::Mode64Bit);
DEBUG(dbgs() << "Subtarget features: SSELevel " << X86SSELevel
<< ", 3DNowLevel " << X863DNowLevel
<< ", 64bit " << HasX86_64 << "\n");
assert((!In64BitMode || HasX86_64) &&
"64-bit code requested on a subtarget that doesn't support it!");
// Stack alignment is 16 bytes on Darwin, FreeBSD, Linux and Solaris (both
// 32 and 64 bit) and for all 64-bit targets.
if (StackAlignOverride)
stackAlignment = StackAlignOverride;
else if (isTargetDarwin() || isTargetFreeBSD() || isTargetLinux() ||
isTargetSolaris() || In64BitMode)
stackAlignment = 16;
}
bool X86Subtarget::enablePostRAScheduler(
CodeGenOpt::Level OptLevel,
TargetSubtargetInfo::AntiDepBreakMode& Mode,
RegClassVector& CriticalPathRCs) const {
Mode = TargetSubtargetInfo::ANTIDEP_CRITICAL;
CriticalPathRCs.clear();
return PostRAScheduler && OptLevel >= CodeGenOpt::Default;
}
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