91 lines
2.9 KiB
C++
91 lines
2.9 KiB
C++
//===---- i386.cpp - Generic JITLink i386 edge kinds, utilities -----===//
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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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// Generic utilities for graphs representing i386 objects.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/ExecutionEngine/JITLink/i386.h"
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#define DEBUG_TYPE "jitlink"
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namespace llvm::jitlink::i386 {
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const char *getEdgeKindName(Edge::Kind K) {
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switch (K) {
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case None:
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return "None";
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case Pointer32:
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return "Pointer32";
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case PCRel32:
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return "PCRel32";
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case Pointer16:
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return "Pointer16";
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case PCRel16:
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return "PCRel16";
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case Delta32:
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return "Delta32";
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case Delta32FromGOT:
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return "Delta32FromGOT";
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case RequestGOTAndTransformToDelta32FromGOT:
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return "RequestGOTAndTransformToDelta32FromGOT";
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case BranchPCRel32:
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return "BranchPCRel32";
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case BranchPCRel32ToPtrJumpStub:
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return "BranchPCRel32ToPtrJumpStub";
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case BranchPCRel32ToPtrJumpStubBypassable:
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return "BranchPCRel32ToPtrJumpStubBypassable";
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}
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return getGenericEdgeKindName(K);
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}
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const char NullPointerContent[PointerSize] = {0x00, 0x00, 0x00, 0x00};
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const char PointerJumpStubContent[6] = {
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static_cast<char>(0xFFu), 0x25, 0x00, 0x00, 0x00, 0x00};
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Error optimizeGOTAndStubAccesses(LinkGraph &G) {
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LLVM_DEBUG(dbgs() << "Optimizing GOT entries and stubs:\n");
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for (auto *B : G.blocks())
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for (auto &E : B->edges()) {
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if (E.getKind() == i386::BranchPCRel32ToPtrJumpStubBypassable) {
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auto &StubBlock = E.getTarget().getBlock();
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assert(StubBlock.getSize() == sizeof(PointerJumpStubContent) &&
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"Stub block should be stub sized");
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assert(StubBlock.edges_size() == 1 &&
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"Stub block should only have one outgoing edge");
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auto &GOTBlock = StubBlock.edges().begin()->getTarget().getBlock();
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assert(GOTBlock.getSize() == G.getPointerSize() &&
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"GOT block should be pointer sized");
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assert(GOTBlock.edges_size() == 1 &&
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"GOT block should only have one outgoing edge");
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auto &GOTTarget = GOTBlock.edges().begin()->getTarget();
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orc::ExecutorAddr EdgeAddr = B->getAddress() + E.getOffset();
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orc::ExecutorAddr TargetAddr = GOTTarget.getAddress();
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int64_t Displacement = TargetAddr - EdgeAddr + 4;
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if (isInt<32>(Displacement)) {
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E.setKind(i386::BranchPCRel32);
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E.setTarget(GOTTarget);
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LLVM_DEBUG({
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dbgs() << " Replaced stub branch with direct branch:\n ";
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printEdge(dbgs(), *B, E, getEdgeKindName(E.getKind()));
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dbgs() << "\n";
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});
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}
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}
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}
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return Error::success();
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}
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} // namespace llvm::jitlink::i386
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