353 lines
12 KiB
C++
353 lines
12 KiB
C++
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//===-- X86Subtarget.cpp - X86 Subtarget Information ----------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the X86 specific subclass of TargetSubtargetInfo.
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//
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//===----------------------------------------------------------------------===//
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#include "X86Subtarget.h"
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#include "MCTargetDesc/X86BaseInfo.h"
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#include "X86.h"
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#include "X86CallLowering.h"
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#include "X86LegalizerInfo.h"
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#include "X86MacroFusion.h"
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#include "X86RegisterBankInfo.h"
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#include "X86TargetMachine.h"
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#include "llvm/ADT/Triple.h"
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#include "llvm/CodeGen/GlobalISel/CallLowering.h"
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#include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
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#include "llvm/IR/Attributes.h"
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#include "llvm/IR/ConstantRange.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/CodeGen.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetMachine.h"
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#if defined(_MSC_VER)
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#include <intrin.h>
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#endif
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using namespace llvm;
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#define DEBUG_TYPE "subtarget"
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#define GET_SUBTARGETINFO_TARGET_DESC
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#define GET_SUBTARGETINFO_CTOR
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#include "X86GenSubtargetInfo.inc"
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// Temporary option to control early if-conversion for x86 while adding machine
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// models.
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static cl::opt<bool>
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X86EarlyIfConv("x86-early-ifcvt", cl::Hidden,
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cl::desc("Enable early if-conversion on X86"));
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/// Classify a blockaddress reference for the current subtarget according to how
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/// we should reference it in a non-pcrel context.
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unsigned char X86Subtarget::classifyBlockAddressReference() const {
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return classifyLocalReference(nullptr);
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}
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/// Classify a global variable reference for the current subtarget according to
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/// how we should reference it in a non-pcrel context.
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unsigned char
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X86Subtarget::classifyGlobalReference(const GlobalValue *GV) const {
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return classifyGlobalReference(GV, *GV->getParent());
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}
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unsigned char
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X86Subtarget::classifyLocalReference(const GlobalValue *GV) const {
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// If we're not PIC, it's not very interesting.
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if (!isPositionIndependent())
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return X86II::MO_NO_FLAG;
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if (is64Bit()) {
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// 64-bit ELF PIC local references may use GOTOFF relocations.
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if (isTargetELF()) {
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switch (TM.getCodeModel()) {
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// 64-bit small code model is simple: All rip-relative.
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case CodeModel::Tiny:
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llvm_unreachable("Tiny codesize model not supported on X86");
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case CodeModel::Small:
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case CodeModel::Kernel:
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return X86II::MO_NO_FLAG;
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// The large PIC code model uses GOTOFF.
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case CodeModel::Large:
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return X86II::MO_GOTOFF;
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// Medium is a hybrid: RIP-rel for code, GOTOFF for DSO local data.
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case CodeModel::Medium:
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// Constant pool and jump table handling pass a nullptr to this
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// function so we need to use isa_and_nonnull.
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if (isa_and_nonnull<Function>(GV))
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return X86II::MO_NO_FLAG; // All code is RIP-relative
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return X86II::MO_GOTOFF; // Local symbols use GOTOFF.
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}
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llvm_unreachable("invalid code model");
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}
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// Otherwise, this is either a RIP-relative reference or a 64-bit movabsq,
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// both of which use MO_NO_FLAG.
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return X86II::MO_NO_FLAG;
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}
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// The COFF dynamic linker just patches the executable sections.
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if (isTargetCOFF())
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return X86II::MO_NO_FLAG;
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if (isTargetDarwin()) {
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// 32 bit macho has no relocation for a-b if a is undefined, even if
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// b is in the section that is being relocated.
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// This means we have to use o load even for GVs that are known to be
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// local to the dso.
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if (GV && (GV->isDeclarationForLinker() || GV->hasCommonLinkage()))
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return X86II::MO_DARWIN_NONLAZY_PIC_BASE;
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return X86II::MO_PIC_BASE_OFFSET;
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}
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return X86II::MO_GOTOFF;
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}
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unsigned char X86Subtarget::classifyGlobalReference(const GlobalValue *GV,
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const Module &M) const {
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// The static large model never uses stubs.
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if (TM.getCodeModel() == CodeModel::Large && !isPositionIndependent())
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return X86II::MO_NO_FLAG;
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// Absolute symbols can be referenced directly.
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if (GV) {
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if (Optional<ConstantRange> CR = GV->getAbsoluteSymbolRange()) {
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// See if we can use the 8-bit immediate form. Note that some instructions
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// will sign extend the immediate operand, so to be conservative we only
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// accept the range [0,128).
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if (CR->getUnsignedMax().ult(128))
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return X86II::MO_ABS8;
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else
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return X86II::MO_NO_FLAG;
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}
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}
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if (TM.shouldAssumeDSOLocal(M, GV))
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return classifyLocalReference(GV);
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if (isTargetCOFF()) {
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if (GV->hasDLLImportStorageClass())
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return X86II::MO_DLLIMPORT;
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return X86II::MO_COFFSTUB;
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}
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// Some JIT users use *-win32-elf triples; these shouldn't use GOT tables.
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if (isOSWindows())
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return X86II::MO_NO_FLAG;
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if (is64Bit()) {
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// ELF supports a large, truly PIC code model with non-PC relative GOT
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// references. Other object file formats do not. Use the no-flag, 64-bit
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// reference for them.
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if (TM.getCodeModel() == CodeModel::Large)
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return isTargetELF() ? X86II::MO_GOT : X86II::MO_NO_FLAG;
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return X86II::MO_GOTPCREL;
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}
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if (isTargetDarwin()) {
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if (!isPositionIndependent())
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return X86II::MO_DARWIN_NONLAZY;
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return X86II::MO_DARWIN_NONLAZY_PIC_BASE;
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}
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// 32-bit ELF references GlobalAddress directly in static relocation model.
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// We cannot use MO_GOT because EBX may not be set up.
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if (TM.getRelocationModel() == Reloc::Static)
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return X86II::MO_NO_FLAG;
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return X86II::MO_GOT;
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}
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unsigned char
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X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV) const {
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return classifyGlobalFunctionReference(GV, *GV->getParent());
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}
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unsigned char
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X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV,
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const Module &M) const {
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if (TM.shouldAssumeDSOLocal(M, GV))
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return X86II::MO_NO_FLAG;
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// Functions on COFF can be non-DSO local for two reasons:
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// - They are marked dllimport
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// - They are extern_weak, and a stub is needed
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if (isTargetCOFF()) {
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if (GV->hasDLLImportStorageClass())
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return X86II::MO_DLLIMPORT;
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return X86II::MO_COFFSTUB;
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}
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const Function *F = dyn_cast_or_null<Function>(GV);
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if (isTargetELF()) {
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if (is64Bit() && F && (CallingConv::X86_RegCall == F->getCallingConv()))
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// According to psABI, PLT stub clobbers XMM8-XMM15.
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// In Regcall calling convention those registers are used for passing
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// parameters. Thus we need to prevent lazy binding in Regcall.
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return X86II::MO_GOTPCREL;
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// If PLT must be avoided then the call should be via GOTPCREL.
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if (((F && F->hasFnAttribute(Attribute::NonLazyBind)) ||
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(!F && M.getRtLibUseGOT())) &&
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is64Bit())
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return X86II::MO_GOTPCREL;
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// Reference ExternalSymbol directly in static relocation model.
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if (!is64Bit() && !GV && TM.getRelocationModel() == Reloc::Static)
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return X86II::MO_NO_FLAG;
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return X86II::MO_PLT;
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}
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if (is64Bit()) {
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if (F && F->hasFnAttribute(Attribute::NonLazyBind))
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// If the function is marked as non-lazy, generate an indirect call
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// which loads from the GOT directly. This avoids runtime overhead
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// at the cost of eager binding (and one extra byte of encoding).
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return X86II::MO_GOTPCREL;
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return X86II::MO_NO_FLAG;
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}
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return X86II::MO_NO_FLAG;
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}
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/// Return true if the subtarget allows calls to immediate address.
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bool X86Subtarget::isLegalToCallImmediateAddr() const {
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// FIXME: I386 PE/COFF supports PC relative calls using IMAGE_REL_I386_REL32
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// but WinCOFFObjectWriter::RecordRelocation cannot emit them. Once it does,
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// the following check for Win32 should be removed.
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if (In64BitMode || isTargetWin32())
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return false;
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return isTargetELF() || TM.getRelocationModel() == Reloc::Static;
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}
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void X86Subtarget::initSubtargetFeatures(StringRef CPU, StringRef TuneCPU,
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StringRef FS) {
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if (CPU.empty())
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CPU = "generic";
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if (TuneCPU.empty())
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TuneCPU = "i586"; // FIXME: "generic" is more modern than llc tests expect.
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std::string FullFS = X86_MC::ParseX86Triple(TargetTriple);
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assert(!FullFS.empty() && "Failed to parse X86 triple");
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if (!FS.empty())
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FullFS = (Twine(FullFS) + "," + FS).str();
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// Parse features string and set the CPU.
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ParseSubtargetFeatures(CPU, TuneCPU, FullFS);
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// All CPUs that implement SSE4.2 or SSE4A support unaligned accesses of
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// 16-bytes and under that are reasonably fast. These features were
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// introduced with Intel's Nehalem/Silvermont and AMD's Family10h
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// micro-architectures respectively.
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if (hasSSE42() || hasSSE4A())
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IsUAMem16Slow = false;
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LLVM_DEBUG(dbgs() << "Subtarget features: SSELevel " << X86SSELevel
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<< ", 3DNowLevel " << X863DNowLevel << ", 64bit "
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<< HasX86_64 << "\n");
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if (In64BitMode && !HasX86_64)
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report_fatal_error("64-bit code requested on a subtarget that doesn't "
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"support it!");
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// Stack alignment is 16 bytes on Darwin, Linux, kFreeBSD and for all
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// 64-bit targets. On Solaris (32-bit), stack alignment is 4 bytes
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// following the i386 psABI, while on Illumos it is always 16 bytes.
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if (StackAlignOverride)
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stackAlignment = *StackAlignOverride;
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else if (isTargetDarwin() || isTargetLinux() || isTargetKFreeBSD() ||
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In64BitMode)
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stackAlignment = Align(16);
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// Consume the vector width attribute or apply any target specific limit.
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if (PreferVectorWidthOverride)
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PreferVectorWidth = PreferVectorWidthOverride;
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else if (Prefer128Bit)
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PreferVectorWidth = 128;
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else if (Prefer256Bit)
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PreferVectorWidth = 256;
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}
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X86Subtarget &X86Subtarget::initializeSubtargetDependencies(StringRef CPU,
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StringRef TuneCPU,
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StringRef FS) {
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initSubtargetFeatures(CPU, TuneCPU, FS);
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return *this;
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}
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X86Subtarget::X86Subtarget(const Triple &TT, StringRef CPU, StringRef TuneCPU,
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StringRef FS, const X86TargetMachine &TM,
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MaybeAlign StackAlignOverride,
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unsigned PreferVectorWidthOverride,
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unsigned RequiredVectorWidth)
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: X86GenSubtargetInfo(TT, CPU, TuneCPU, FS),
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PICStyle(PICStyles::Style::None), TM(TM), TargetTriple(TT),
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StackAlignOverride(StackAlignOverride),
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PreferVectorWidthOverride(PreferVectorWidthOverride),
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RequiredVectorWidth(RequiredVectorWidth),
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InstrInfo(initializeSubtargetDependencies(CPU, TuneCPU, FS)),
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TLInfo(TM, *this), FrameLowering(*this, getStackAlignment()) {
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// Determine the PICStyle based on the target selected.
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if (!isPositionIndependent())
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setPICStyle(PICStyles::Style::None);
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else if (is64Bit())
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setPICStyle(PICStyles::Style::RIPRel);
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else if (isTargetCOFF())
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setPICStyle(PICStyles::Style::None);
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else if (isTargetDarwin())
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setPICStyle(PICStyles::Style::StubPIC);
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else if (isTargetELF())
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setPICStyle(PICStyles::Style::GOT);
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CallLoweringInfo.reset(new X86CallLowering(*getTargetLowering()));
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Legalizer.reset(new X86LegalizerInfo(*this, TM));
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auto *RBI = new X86RegisterBankInfo(*getRegisterInfo());
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RegBankInfo.reset(RBI);
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InstSelector.reset(createX86InstructionSelector(TM, *this, *RBI));
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}
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const CallLowering *X86Subtarget::getCallLowering() const {
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return CallLoweringInfo.get();
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}
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InstructionSelector *X86Subtarget::getInstructionSelector() const {
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return InstSelector.get();
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}
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const LegalizerInfo *X86Subtarget::getLegalizerInfo() const {
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return Legalizer.get();
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}
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const RegisterBankInfo *X86Subtarget::getRegBankInfo() const {
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return RegBankInfo.get();
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}
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bool X86Subtarget::enableEarlyIfConversion() const {
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return hasCMov() && X86EarlyIfConv;
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}
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void X86Subtarget::getPostRAMutations(
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std::vector<std::unique_ptr<ScheduleDAGMutation>> &Mutations) const {
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Mutations.push_back(createX86MacroFusionDAGMutation());
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}
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bool X86Subtarget::isPositionIndependent() const {
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return TM.isPositionIndependent();
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}
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