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//===-------- x86.cpp - Generic JITLink x86 edge kinds, utilities ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Generic utilities for graphs representing x86 objects.
//
//===----------------------------------------------------------------------===//
#include "llvm/ExecutionEngine/JITLink/x86.h"
#define DEBUG_TYPE "jitlink"
namespace llvm::jitlink::x86 {
const char *getEdgeKindName(Edge::Kind K) {
switch (K) {
case Pointer32:
return "Pointer32";
case PCRel32:
return "PCRel32";
case Pointer16:
return "Pointer16";
case PCRel16:
return "PCRel16";
case Delta32:
return "Delta32";
case Delta32FromGOT:
return "Delta32FromGOT";
case RequestGOTAndTransformToDelta32FromGOT:
return "RequestGOTAndTransformToDelta32FromGOT";
case BranchPCRel32:
return "BranchPCRel32";
case BranchPCRel32ToPtrJumpStub:
return "BranchPCRel32ToPtrJumpStub";
case BranchPCRel32ToPtrJumpStubBypassable:
return "BranchPCRel32ToPtrJumpStubBypassable";
}
return getGenericEdgeKindName(K);
}
const char NullPointerContent[PointerSize] = {0x00, 0x00, 0x00, 0x00};
const char PointerJumpStubContent[6] = {
static_cast<char>(0xFFu), 0x25, 0x00, 0x00, 0x00, 0x00};
Error optimizeGOTAndStubAccesses(LinkGraph &G) {
LLVM_DEBUG(dbgs() << "Optimizing GOT entries and stubs:\n");
for (auto *B : G.blocks())
for (auto &E : B->edges()) {
if (E.getKind() == BranchPCRel32ToPtrJumpStubBypassable) {
auto &StubBlock = E.getTarget().getBlock();
assert(StubBlock.getSize() == sizeof(PointerJumpStubContent) &&
"Stub block should be stub sized");
assert(StubBlock.edges_size() == 1 &&
"Stub block should only have one outgoing edge");
auto &GOTBlock = StubBlock.edges().begin()->getTarget().getBlock();
assert(GOTBlock.getSize() == G.getPointerSize() &&
"GOT block should be pointer sized");
assert(GOTBlock.edges_size() == 1 &&
"GOT block should only have one outgoing edge");
auto &GOTTarget = GOTBlock.edges().begin()->getTarget();
orc::ExecutorAddr EdgeAddr = B->getAddress() + E.getOffset();
orc::ExecutorAddr TargetAddr = GOTTarget.getAddress();
int64_t Displacement = TargetAddr - EdgeAddr + 4;
if (isInt<32>(Displacement)) {
E.setKind(BranchPCRel32);
E.setTarget(GOTTarget);
LLVM_DEBUG({
dbgs() << " Replaced stub branch with direct branch:\n ";
printEdge(dbgs(), *B, E, getEdgeKindName(E.getKind()));
dbgs() << "\n";
});
}
}
}
return Error::success();
}
} // namespace llvm::jitlink::x86
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