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3f4c58083e
Infrastructure designed for padding code with nop instructions in key places such that preformance improvement will be achieved. The infrastructure is implemented such that the padding is done in the Assembler after the layout is done and all IPs and alignments are known. This patch by itself in a NFC. Future patches will make use of this infrastructure to implement required policies for code padding. Reviewers: aaboud zvi craig.topper gadi.haber Differential revision: https://reviews.llvm.org/D34393 Change-Id: I92110d0c0a757080a8405636914a93ef6f8ad00e llvm-svn: 316413
489 lines
15 KiB
C++
489 lines
15 KiB
C++
//===- lib/MC/MCFragment.cpp - Assembler Fragment Implementation ----------===//
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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 "llvm/MC/MCFragment.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/StringExtras.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/MC/MCAsmLayout.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCFixup.h"
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#include "llvm/MC/MCSection.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCValue.h"
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#include "llvm/Support/Casting.h"
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#include "llvm/Support/Compiler.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 <cassert>
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#include <cstdint>
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#include <utility>
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using namespace llvm;
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MCAsmLayout::MCAsmLayout(MCAssembler &Asm) : Assembler(Asm) {
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// Compute the section layout order. Virtual sections must go last.
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for (MCSection &Sec : Asm)
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if (!Sec.isVirtualSection())
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SectionOrder.push_back(&Sec);
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for (MCSection &Sec : Asm)
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if (Sec.isVirtualSection())
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SectionOrder.push_back(&Sec);
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}
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bool MCAsmLayout::isFragmentValid(const MCFragment *F) const {
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const MCSection *Sec = F->getParent();
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const MCFragment *LastValid = LastValidFragment.lookup(Sec);
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if (!LastValid)
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return false;
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assert(LastValid->getParent() == Sec);
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return F->getLayoutOrder() <= LastValid->getLayoutOrder();
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}
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void MCAsmLayout::invalidateFragmentsFrom(MCFragment *F) {
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// If this fragment wasn't already valid, we don't need to do anything.
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if (!isFragmentValid(F))
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return;
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// Otherwise, reset the last valid fragment to the previous fragment
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// (if this is the first fragment, it will be NULL).
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LastValidFragment[F->getParent()] = F->getPrevNode();
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}
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void MCAsmLayout::ensureValid(const MCFragment *F) const {
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MCSection *Sec = F->getParent();
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MCSection::iterator I;
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if (MCFragment *Cur = LastValidFragment[Sec])
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I = ++MCSection::iterator(Cur);
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else
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I = Sec->begin();
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// Advance the layout position until the fragment is valid.
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while (!isFragmentValid(F)) {
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assert(I != Sec->end() && "Layout bookkeeping error");
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const_cast<MCAsmLayout *>(this)->layoutFragment(&*I);
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++I;
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}
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}
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uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
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ensureValid(F);
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assert(F->Offset != ~UINT64_C(0) && "Address not set!");
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return F->Offset;
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}
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// Simple getSymbolOffset helper for the non-variable case.
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static bool getLabelOffset(const MCAsmLayout &Layout, const MCSymbol &S,
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bool ReportError, uint64_t &Val) {
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if (!S.getFragment()) {
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if (ReportError)
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report_fatal_error("unable to evaluate offset to undefined symbol '" +
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S.getName() + "'");
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return false;
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}
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Val = Layout.getFragmentOffset(S.getFragment()) + S.getOffset();
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return true;
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}
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static bool getSymbolOffsetImpl(const MCAsmLayout &Layout, const MCSymbol &S,
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bool ReportError, uint64_t &Val) {
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if (!S.isVariable())
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return getLabelOffset(Layout, S, ReportError, Val);
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// If SD is a variable, evaluate it.
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MCValue Target;
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if (!S.getVariableValue()->evaluateAsValue(Target, Layout))
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report_fatal_error("unable to evaluate offset for variable '" +
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S.getName() + "'");
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uint64_t Offset = Target.getConstant();
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const MCSymbolRefExpr *A = Target.getSymA();
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if (A) {
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uint64_t ValA;
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if (!getLabelOffset(Layout, A->getSymbol(), ReportError, ValA))
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return false;
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Offset += ValA;
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}
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const MCSymbolRefExpr *B = Target.getSymB();
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if (B) {
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uint64_t ValB;
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if (!getLabelOffset(Layout, B->getSymbol(), ReportError, ValB))
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return false;
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Offset -= ValB;
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}
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Val = Offset;
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return true;
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}
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bool MCAsmLayout::getSymbolOffset(const MCSymbol &S, uint64_t &Val) const {
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return getSymbolOffsetImpl(*this, S, false, Val);
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}
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uint64_t MCAsmLayout::getSymbolOffset(const MCSymbol &S) const {
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uint64_t Val;
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getSymbolOffsetImpl(*this, S, true, Val);
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return Val;
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}
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const MCSymbol *MCAsmLayout::getBaseSymbol(const MCSymbol &Symbol) const {
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if (!Symbol.isVariable())
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return &Symbol;
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const MCExpr *Expr = Symbol.getVariableValue();
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MCValue Value;
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if (!Expr->evaluateAsValue(Value, *this)) {
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Assembler.getContext().reportError(
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Expr->getLoc(), "expression could not be evaluated");
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return nullptr;
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}
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const MCSymbolRefExpr *RefB = Value.getSymB();
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if (RefB) {
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Assembler.getContext().reportError(
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Expr->getLoc(), Twine("symbol '") + RefB->getSymbol().getName() +
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"' could not be evaluated in a subtraction expression");
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return nullptr;
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}
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const MCSymbolRefExpr *A = Value.getSymA();
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if (!A)
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return nullptr;
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const MCSymbol &ASym = A->getSymbol();
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const MCAssembler &Asm = getAssembler();
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if (ASym.isCommon()) {
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Asm.getContext().reportError(Expr->getLoc(),
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"Common symbol '" + ASym.getName() +
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"' cannot be used in assignment expr");
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return nullptr;
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}
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return &ASym;
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}
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uint64_t MCAsmLayout::getSectionAddressSize(const MCSection *Sec) const {
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// The size is the last fragment's end offset.
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const MCFragment &F = Sec->getFragmentList().back();
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return getFragmentOffset(&F) + getAssembler().computeFragmentSize(*this, F);
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}
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uint64_t MCAsmLayout::getSectionFileSize(const MCSection *Sec) const {
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// Virtual sections have no file size.
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if (Sec->isVirtualSection())
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return 0;
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// Otherwise, the file size is the same as the address space size.
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return getSectionAddressSize(Sec);
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}
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uint64_t llvm::computeBundlePadding(const MCAssembler &Assembler,
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const MCFragment *F,
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uint64_t FOffset, uint64_t FSize) {
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uint64_t BundleSize = Assembler.getBundleAlignSize();
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assert(BundleSize > 0 &&
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"computeBundlePadding should only be called if bundling is enabled");
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uint64_t BundleMask = BundleSize - 1;
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uint64_t OffsetInBundle = FOffset & BundleMask;
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uint64_t EndOfFragment = OffsetInBundle + FSize;
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// There are two kinds of bundling restrictions:
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//
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// 1) For alignToBundleEnd(), add padding to ensure that the fragment will
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// *end* on a bundle boundary.
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// 2) Otherwise, check if the fragment would cross a bundle boundary. If it
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// would, add padding until the end of the bundle so that the fragment
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// will start in a new one.
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if (F->alignToBundleEnd()) {
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// Three possibilities here:
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//
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// A) The fragment just happens to end at a bundle boundary, so we're good.
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// B) The fragment ends before the current bundle boundary: pad it just
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// enough to reach the boundary.
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// C) The fragment ends after the current bundle boundary: pad it until it
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// reaches the end of the next bundle boundary.
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//
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// Note: this code could be made shorter with some modulo trickery, but it's
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// intentionally kept in its more explicit form for simplicity.
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if (EndOfFragment == BundleSize)
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return 0;
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else if (EndOfFragment < BundleSize)
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return BundleSize - EndOfFragment;
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else { // EndOfFragment > BundleSize
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return 2 * BundleSize - EndOfFragment;
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}
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} else if (OffsetInBundle > 0 && EndOfFragment > BundleSize)
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return BundleSize - OffsetInBundle;
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else
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return 0;
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}
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/* *** */
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void ilist_alloc_traits<MCFragment>::deleteNode(MCFragment *V) { V->destroy(); }
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MCFragment::~MCFragment() = default;
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MCFragment::MCFragment(FragmentType Kind, bool HasInstructions,
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uint8_t BundlePadding, MCSection *Parent)
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: Kind(Kind), HasInstructions(HasInstructions), AlignToBundleEnd(false),
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BundlePadding(BundlePadding), Parent(Parent), Atom(nullptr),
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Offset(~UINT64_C(0)) {
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if (Parent && !isDummy())
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Parent->getFragmentList().push_back(this);
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}
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void MCFragment::destroy() {
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// First check if we are the sentinal.
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if (Kind == FragmentType(~0)) {
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delete this;
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return;
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}
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switch (Kind) {
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case FT_Align:
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delete cast<MCAlignFragment>(this);
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return;
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case FT_Data:
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delete cast<MCDataFragment>(this);
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return;
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case FT_CompactEncodedInst:
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delete cast<MCCompactEncodedInstFragment>(this);
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return;
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case FT_Fill:
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delete cast<MCFillFragment>(this);
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return;
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case FT_Relaxable:
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delete cast<MCRelaxableFragment>(this);
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return;
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case FT_Org:
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delete cast<MCOrgFragment>(this);
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return;
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case FT_Dwarf:
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delete cast<MCDwarfLineAddrFragment>(this);
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return;
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case FT_DwarfFrame:
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delete cast<MCDwarfCallFrameFragment>(this);
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return;
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case FT_LEB:
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delete cast<MCLEBFragment>(this);
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return;
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case FT_Padding:
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delete cast<MCPaddingFragment>(this);
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return;
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case FT_SafeSEH:
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delete cast<MCSafeSEHFragment>(this);
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return;
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case FT_CVInlineLines:
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delete cast<MCCVInlineLineTableFragment>(this);
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return;
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case FT_CVDefRange:
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delete cast<MCCVDefRangeFragment>(this);
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return;
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case FT_Dummy:
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delete cast<MCDummyFragment>(this);
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return;
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}
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}
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// Debugging methods
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namespace llvm {
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raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
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OS << "<MCFixup" << " Offset:" << AF.getOffset()
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<< " Value:" << *AF.getValue()
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<< " Kind:" << AF.getKind() << ">";
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return OS;
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}
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} // end namespace llvm
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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LLVM_DUMP_METHOD void MCFragment::dump() const {
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raw_ostream &OS = errs();
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OS << "<";
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switch (getKind()) {
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case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
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case MCFragment::FT_Data: OS << "MCDataFragment"; break;
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case MCFragment::FT_CompactEncodedInst:
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OS << "MCCompactEncodedInstFragment"; break;
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case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
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case MCFragment::FT_Relaxable: OS << "MCRelaxableFragment"; break;
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case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
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case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
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case MCFragment::FT_DwarfFrame: OS << "MCDwarfCallFrameFragment"; break;
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case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
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case MCFragment::FT_Padding: OS << "MCPaddingFragment"; break;
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case MCFragment::FT_SafeSEH: OS << "MCSafeSEHFragment"; break;
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case MCFragment::FT_CVInlineLines: OS << "MCCVInlineLineTableFragment"; break;
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case MCFragment::FT_CVDefRange: OS << "MCCVDefRangeTableFragment"; break;
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case MCFragment::FT_Dummy: OS << "MCDummyFragment"; break;
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}
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OS << "<MCFragment " << (const void*) this << " LayoutOrder:" << LayoutOrder
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<< " Offset:" << Offset
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<< " HasInstructions:" << hasInstructions()
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<< " BundlePadding:" << static_cast<unsigned>(getBundlePadding()) << ">";
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switch (getKind()) {
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case MCFragment::FT_Align: {
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const MCAlignFragment *AF = cast<MCAlignFragment>(this);
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if (AF->hasEmitNops())
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OS << " (emit nops)";
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OS << "\n ";
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OS << " Alignment:" << AF->getAlignment()
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<< " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
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<< " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
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break;
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}
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case MCFragment::FT_Data: {
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const MCDataFragment *DF = cast<MCDataFragment>(this);
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OS << "\n ";
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OS << " Contents:[";
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const SmallVectorImpl<char> &Contents = DF->getContents();
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for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
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if (i) OS << ",";
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OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
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}
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OS << "] (" << Contents.size() << " bytes)";
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if (DF->fixup_begin() != DF->fixup_end()) {
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OS << ",\n ";
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OS << " Fixups:[";
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for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
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ie = DF->fixup_end(); it != ie; ++it) {
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if (it != DF->fixup_begin()) OS << ",\n ";
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OS << *it;
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}
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OS << "]";
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}
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break;
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}
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case MCFragment::FT_CompactEncodedInst: {
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const MCCompactEncodedInstFragment *CEIF =
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cast<MCCompactEncodedInstFragment>(this);
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OS << "\n ";
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OS << " Contents:[";
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const SmallVectorImpl<char> &Contents = CEIF->getContents();
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for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
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if (i) OS << ",";
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OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
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}
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OS << "] (" << Contents.size() << " bytes)";
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break;
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}
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case MCFragment::FT_Fill: {
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const MCFillFragment *FF = cast<MCFillFragment>(this);
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OS << " Value:" << static_cast<unsigned>(FF->getValue())
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<< " Size:" << FF->getSize();
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break;
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}
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case MCFragment::FT_Relaxable: {
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const MCRelaxableFragment *F = cast<MCRelaxableFragment>(this);
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OS << "\n ";
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OS << " Inst:";
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F->getInst().dump_pretty(OS);
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break;
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}
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case MCFragment::FT_Org: {
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const MCOrgFragment *OF = cast<MCOrgFragment>(this);
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OS << "\n ";
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OS << " Offset:" << OF->getOffset()
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<< " Value:" << static_cast<unsigned>(OF->getValue());
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break;
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}
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case MCFragment::FT_Dwarf: {
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const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
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OS << "\n ";
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OS << " AddrDelta:" << OF->getAddrDelta()
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<< " LineDelta:" << OF->getLineDelta();
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break;
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}
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case MCFragment::FT_DwarfFrame: {
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const MCDwarfCallFrameFragment *CF = cast<MCDwarfCallFrameFragment>(this);
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OS << "\n ";
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OS << " AddrDelta:" << CF->getAddrDelta();
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break;
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}
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case MCFragment::FT_LEB: {
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const MCLEBFragment *LF = cast<MCLEBFragment>(this);
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OS << "\n ";
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OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
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break;
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}
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case MCFragment::FT_Padding: {
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const MCPaddingFragment *F = cast<MCPaddingFragment>(this);
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OS << "\n ";
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OS << " PaddingPoliciesMask:" << F->getPaddingPoliciesMask()
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<< " IsInsertionPoint:" << F->isInsertionPoint()
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<< " Size:" << F->getSize();
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OS << "\n ";
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OS << " Inst:";
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F->getInst().dump_pretty(OS);
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OS << " InstSize:" << F->getInstSize();
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OS << "\n ";
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break;
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}
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case MCFragment::FT_SafeSEH: {
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const MCSafeSEHFragment *F = cast<MCSafeSEHFragment>(this);
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OS << "\n ";
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OS << " Sym:" << F->getSymbol();
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break;
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}
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case MCFragment::FT_CVInlineLines: {
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const auto *F = cast<MCCVInlineLineTableFragment>(this);
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OS << "\n ";
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OS << " Sym:" << *F->getFnStartSym();
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break;
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}
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case MCFragment::FT_CVDefRange: {
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const auto *F = cast<MCCVDefRangeFragment>(this);
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OS << "\n ";
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for (std::pair<const MCSymbol *, const MCSymbol *> RangeStartEnd :
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F->getRanges()) {
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OS << " RangeStart:" << RangeStartEnd.first;
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OS << " RangeEnd:" << RangeStartEnd.second;
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}
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break;
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}
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case MCFragment::FT_Dummy:
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break;
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}
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OS << ">";
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}
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LLVM_DUMP_METHOD void MCAssembler::dump() const{
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raw_ostream &OS = errs();
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OS << "<MCAssembler\n";
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OS << " Sections:[\n ";
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for (const_iterator it = begin(), ie = end(); it != ie; ++it) {
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if (it != begin()) OS << ",\n ";
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it->dump();
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}
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OS << "],\n";
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OS << " Symbols:[";
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for (const_symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
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if (it != symbol_begin()) OS << ",\n ";
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OS << "(";
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it->dump();
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OS << ", Index:" << it->getIndex() << ", ";
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OS << ")";
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}
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OS << "]>\n";
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}
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#endif
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