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1130 lines
38 KiB
1130 lines
38 KiB
//===- lib/MC/MCWin64EH.cpp - MCWin64EH implementation --------------------===//
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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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#include "llvm/MC/MCWin64EH.h"
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#include "llvm/ADT/Twine.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/MCObjectFileInfo.h"
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#include "llvm/MC/MCObjectStreamer.h"
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#include "llvm/MC/MCSectionCOFF.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/Support/Win64EH.h"
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using namespace llvm;
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// NOTE: All relocations generated here are 4-byte image-relative.
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static uint8_t CountOfUnwindCodes(std::vector<WinEH::Instruction> &Insns) {
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uint8_t Count = 0;
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for (const auto &I : Insns) {
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switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
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default:
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llvm_unreachable("Unsupported unwind code");
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case Win64EH::UOP_PushNonVol:
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case Win64EH::UOP_AllocSmall:
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case Win64EH::UOP_SetFPReg:
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case Win64EH::UOP_PushMachFrame:
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Count += 1;
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break;
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case Win64EH::UOP_SaveNonVol:
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case Win64EH::UOP_SaveXMM128:
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Count += 2;
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break;
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case Win64EH::UOP_SaveNonVolBig:
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case Win64EH::UOP_SaveXMM128Big:
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Count += 3;
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break;
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case Win64EH::UOP_AllocLarge:
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Count += (I.Offset > 512 * 1024 - 8) ? 3 : 2;
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break;
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}
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}
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return Count;
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}
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static void EmitAbsDifference(MCStreamer &Streamer, const MCSymbol *LHS,
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const MCSymbol *RHS) {
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MCContext &Context = Streamer.getContext();
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const MCExpr *Diff =
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MCBinaryExpr::createSub(MCSymbolRefExpr::create(LHS, Context),
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MCSymbolRefExpr::create(RHS, Context), Context);
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Streamer.emitValue(Diff, 1);
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}
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static void EmitUnwindCode(MCStreamer &streamer, const MCSymbol *begin,
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WinEH::Instruction &inst) {
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uint8_t b2;
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uint16_t w;
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b2 = (inst.Operation & 0x0F);
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switch (static_cast<Win64EH::UnwindOpcodes>(inst.Operation)) {
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default:
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llvm_unreachable("Unsupported unwind code");
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case Win64EH::UOP_PushNonVol:
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EmitAbsDifference(streamer, inst.Label, begin);
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b2 |= (inst.Register & 0x0F) << 4;
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streamer.emitInt8(b2);
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break;
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case Win64EH::UOP_AllocLarge:
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EmitAbsDifference(streamer, inst.Label, begin);
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if (inst.Offset > 512 * 1024 - 8) {
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b2 |= 0x10;
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streamer.emitInt8(b2);
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w = inst.Offset & 0xFFF8;
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streamer.emitInt16(w);
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w = inst.Offset >> 16;
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} else {
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streamer.emitInt8(b2);
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w = inst.Offset >> 3;
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}
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streamer.emitInt16(w);
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break;
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case Win64EH::UOP_AllocSmall:
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b2 |= (((inst.Offset - 8) >> 3) & 0x0F) << 4;
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EmitAbsDifference(streamer, inst.Label, begin);
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streamer.emitInt8(b2);
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break;
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case Win64EH::UOP_SetFPReg:
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EmitAbsDifference(streamer, inst.Label, begin);
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streamer.emitInt8(b2);
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break;
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case Win64EH::UOP_SaveNonVol:
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case Win64EH::UOP_SaveXMM128:
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b2 |= (inst.Register & 0x0F) << 4;
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EmitAbsDifference(streamer, inst.Label, begin);
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streamer.emitInt8(b2);
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w = inst.Offset >> 3;
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if (inst.Operation == Win64EH::UOP_SaveXMM128)
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w >>= 1;
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streamer.emitInt16(w);
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break;
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case Win64EH::UOP_SaveNonVolBig:
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case Win64EH::UOP_SaveXMM128Big:
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b2 |= (inst.Register & 0x0F) << 4;
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EmitAbsDifference(streamer, inst.Label, begin);
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streamer.emitInt8(b2);
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if (inst.Operation == Win64EH::UOP_SaveXMM128Big)
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w = inst.Offset & 0xFFF0;
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else
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w = inst.Offset & 0xFFF8;
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streamer.emitInt16(w);
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w = inst.Offset >> 16;
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streamer.emitInt16(w);
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break;
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case Win64EH::UOP_PushMachFrame:
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if (inst.Offset == 1)
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b2 |= 0x10;
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EmitAbsDifference(streamer, inst.Label, begin);
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streamer.emitInt8(b2);
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break;
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}
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}
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static void EmitSymbolRefWithOfs(MCStreamer &streamer,
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const MCSymbol *Base,
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const MCSymbol *Other) {
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MCContext &Context = streamer.getContext();
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const MCSymbolRefExpr *BaseRef = MCSymbolRefExpr::create(Base, Context);
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const MCSymbolRefExpr *OtherRef = MCSymbolRefExpr::create(Other, Context);
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const MCExpr *Ofs = MCBinaryExpr::createSub(OtherRef, BaseRef, Context);
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const MCSymbolRefExpr *BaseRefRel = MCSymbolRefExpr::create(Base,
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MCSymbolRefExpr::VK_COFF_IMGREL32,
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Context);
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streamer.emitValue(MCBinaryExpr::createAdd(BaseRefRel, Ofs, Context), 4);
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}
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static void EmitRuntimeFunction(MCStreamer &streamer,
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const WinEH::FrameInfo *info) {
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MCContext &context = streamer.getContext();
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streamer.emitValueToAlignment(4);
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EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
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EmitSymbolRefWithOfs(streamer, info->Function, info->End);
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streamer.emitValue(MCSymbolRefExpr::create(info->Symbol,
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MCSymbolRefExpr::VK_COFF_IMGREL32,
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context), 4);
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}
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static void EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info) {
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// If this UNWIND_INFO already has a symbol, it's already been emitted.
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if (info->Symbol)
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return;
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MCContext &context = streamer.getContext();
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MCSymbol *Label = context.createTempSymbol();
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streamer.emitValueToAlignment(4);
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streamer.emitLabel(Label);
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info->Symbol = Label;
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// Upper 3 bits are the version number (currently 1).
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uint8_t flags = 0x01;
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if (info->ChainedParent)
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flags |= Win64EH::UNW_ChainInfo << 3;
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else {
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if (info->HandlesUnwind)
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flags |= Win64EH::UNW_TerminateHandler << 3;
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if (info->HandlesExceptions)
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flags |= Win64EH::UNW_ExceptionHandler << 3;
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}
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streamer.emitInt8(flags);
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if (info->PrologEnd)
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EmitAbsDifference(streamer, info->PrologEnd, info->Begin);
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else
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streamer.emitInt8(0);
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uint8_t numCodes = CountOfUnwindCodes(info->Instructions);
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streamer.emitInt8(numCodes);
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uint8_t frame = 0;
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if (info->LastFrameInst >= 0) {
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WinEH::Instruction &frameInst = info->Instructions[info->LastFrameInst];
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assert(frameInst.Operation == Win64EH::UOP_SetFPReg);
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frame = (frameInst.Register & 0x0F) | (frameInst.Offset & 0xF0);
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}
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streamer.emitInt8(frame);
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// Emit unwind instructions (in reverse order).
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uint8_t numInst = info->Instructions.size();
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for (uint8_t c = 0; c < numInst; ++c) {
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WinEH::Instruction inst = info->Instructions.back();
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info->Instructions.pop_back();
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EmitUnwindCode(streamer, info->Begin, inst);
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}
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// For alignment purposes, the instruction array will always have an even
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// number of entries, with the final entry potentially unused (in which case
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// the array will be one longer than indicated by the count of unwind codes
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// field).
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if (numCodes & 1) {
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streamer.emitInt16(0);
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}
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if (flags & (Win64EH::UNW_ChainInfo << 3))
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EmitRuntimeFunction(streamer, info->ChainedParent);
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else if (flags &
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((Win64EH::UNW_TerminateHandler|Win64EH::UNW_ExceptionHandler) << 3))
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streamer.emitValue(MCSymbolRefExpr::create(info->ExceptionHandler,
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MCSymbolRefExpr::VK_COFF_IMGREL32,
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context), 4);
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else if (numCodes == 0) {
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// The minimum size of an UNWIND_INFO struct is 8 bytes. If we're not
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// a chained unwind info, if there is no handler, and if there are fewer
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// than 2 slots used in the unwind code array, we have to pad to 8 bytes.
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streamer.emitInt32(0);
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}
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}
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void llvm::Win64EH::UnwindEmitter::Emit(MCStreamer &Streamer) const {
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// Emit the unwind info structs first.
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for (const auto &CFI : Streamer.getWinFrameInfos()) {
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MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
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Streamer.SwitchSection(XData);
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::EmitUnwindInfo(Streamer, CFI.get());
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}
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// Now emit RUNTIME_FUNCTION entries.
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for (const auto &CFI : Streamer.getWinFrameInfos()) {
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MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
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Streamer.SwitchSection(PData);
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EmitRuntimeFunction(Streamer, CFI.get());
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}
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}
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void llvm::Win64EH::UnwindEmitter::EmitUnwindInfo(MCStreamer &Streamer,
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WinEH::FrameInfo *info,
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bool HandlerData) const {
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// Switch sections (the static function above is meant to be called from
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// here and from Emit().
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MCSection *XData = Streamer.getAssociatedXDataSection(info->TextSection);
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Streamer.SwitchSection(XData);
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::EmitUnwindInfo(Streamer, info);
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}
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static int64_t GetAbsDifference(MCStreamer &Streamer, const MCSymbol *LHS,
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const MCSymbol *RHS) {
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MCContext &Context = Streamer.getContext();
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const MCExpr *Diff =
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MCBinaryExpr::createSub(MCSymbolRefExpr::create(LHS, Context),
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MCSymbolRefExpr::create(RHS, Context), Context);
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MCObjectStreamer *OS = (MCObjectStreamer *)(&Streamer);
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// It should normally be possible to calculate the length of a function
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// at this point, but it might not be possible in the presence of certain
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// unusual constructs, like an inline asm with an alignment directive.
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int64_t value;
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if (!Diff->evaluateAsAbsolute(value, OS->getAssembler()))
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report_fatal_error("Failed to evaluate function length in SEH unwind info");
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return value;
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}
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static uint32_t ARM64CountOfUnwindCodes(ArrayRef<WinEH::Instruction> Insns) {
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uint32_t Count = 0;
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for (const auto &I : Insns) {
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switch (static_cast<Win64EH::UnwindOpcodes>(I.Operation)) {
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default:
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llvm_unreachable("Unsupported ARM64 unwind code");
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case Win64EH::UOP_AllocSmall:
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Count += 1;
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break;
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case Win64EH::UOP_AllocMedium:
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Count += 2;
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break;
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case Win64EH::UOP_AllocLarge:
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Count += 4;
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break;
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case Win64EH::UOP_SaveR19R20X:
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Count += 1;
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break;
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case Win64EH::UOP_SaveFPLRX:
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Count += 1;
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break;
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case Win64EH::UOP_SaveFPLR:
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Count += 1;
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break;
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case Win64EH::UOP_SaveReg:
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Count += 2;
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break;
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case Win64EH::UOP_SaveRegP:
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Count += 2;
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break;
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case Win64EH::UOP_SaveRegPX:
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Count += 2;
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break;
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case Win64EH::UOP_SaveRegX:
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Count += 2;
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break;
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case Win64EH::UOP_SaveLRPair:
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Count += 2;
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break;
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case Win64EH::UOP_SaveFReg:
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Count += 2;
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break;
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case Win64EH::UOP_SaveFRegP:
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Count += 2;
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break;
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case Win64EH::UOP_SaveFRegX:
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Count += 2;
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break;
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case Win64EH::UOP_SaveFRegPX:
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Count += 2;
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break;
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case Win64EH::UOP_SetFP:
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Count += 1;
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break;
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case Win64EH::UOP_AddFP:
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Count += 2;
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break;
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case Win64EH::UOP_Nop:
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Count += 1;
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break;
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case Win64EH::UOP_End:
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Count += 1;
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break;
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case Win64EH::UOP_SaveNext:
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Count += 1;
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break;
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case Win64EH::UOP_TrapFrame:
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Count += 1;
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break;
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case Win64EH::UOP_PushMachFrame:
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Count += 1;
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break;
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case Win64EH::UOP_Context:
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Count += 1;
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break;
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case Win64EH::UOP_ClearUnwoundToCall:
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Count += 1;
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break;
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}
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}
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return Count;
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}
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// Unwind opcode encodings and restrictions are documented at
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// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
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static void ARM64EmitUnwindCode(MCStreamer &streamer, const MCSymbol *begin,
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WinEH::Instruction &inst) {
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uint8_t b, reg;
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switch (static_cast<Win64EH::UnwindOpcodes>(inst.Operation)) {
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default:
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llvm_unreachable("Unsupported ARM64 unwind code");
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case Win64EH::UOP_AllocSmall:
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b = (inst.Offset >> 4) & 0x1F;
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_AllocMedium: {
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uint16_t hw = (inst.Offset >> 4) & 0x7FF;
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b = 0xC0;
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b |= (hw >> 8);
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streamer.emitInt8(b);
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b = hw & 0xFF;
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streamer.emitInt8(b);
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break;
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}
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case Win64EH::UOP_AllocLarge: {
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uint32_t w;
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b = 0xE0;
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streamer.emitInt8(b);
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w = inst.Offset >> 4;
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b = (w & 0x00FF0000) >> 16;
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streamer.emitInt8(b);
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b = (w & 0x0000FF00) >> 8;
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streamer.emitInt8(b);
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b = w & 0x000000FF;
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streamer.emitInt8(b);
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break;
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}
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case Win64EH::UOP_SetFP:
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b = 0xE1;
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_AddFP:
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b = 0xE2;
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streamer.emitInt8(b);
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b = (inst.Offset >> 3);
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_Nop:
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b = 0xE3;
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveR19R20X:
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b = 0x20;
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b |= (inst.Offset >> 3) & 0x1F;
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveFPLRX:
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b = 0x80;
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b |= ((inst.Offset - 1) >> 3) & 0x3F;
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveFPLR:
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b = 0x40;
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b |= (inst.Offset >> 3) & 0x3F;
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveReg:
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assert(inst.Register >= 19 && "Saved reg must be >= 19");
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reg = inst.Register - 19;
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b = 0xD0 | ((reg & 0xC) >> 2);
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streamer.emitInt8(b);
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b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveRegX:
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assert(inst.Register >= 19 && "Saved reg must be >= 19");
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reg = inst.Register - 19;
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b = 0xD4 | ((reg & 0x8) >> 3);
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streamer.emitInt8(b);
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b = ((reg & 0x7) << 5) | ((inst.Offset >> 3) - 1);
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveRegP:
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assert(inst.Register >= 19 && "Saved registers must be >= 19");
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reg = inst.Register - 19;
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b = 0xC8 | ((reg & 0xC) >> 2);
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streamer.emitInt8(b);
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b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveRegPX:
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assert(inst.Register >= 19 && "Saved registers must be >= 19");
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reg = inst.Register - 19;
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b = 0xCC | ((reg & 0xC) >> 2);
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streamer.emitInt8(b);
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b = ((reg & 0x3) << 6) | ((inst.Offset >> 3) - 1);
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveLRPair:
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assert(inst.Register >= 19 && "Saved reg must be >= 19");
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reg = inst.Register - 19;
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assert((reg % 2) == 0 && "Saved reg must be 19+2*X");
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reg /= 2;
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b = 0xD6 | ((reg & 0x7) >> 2);
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streamer.emitInt8(b);
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b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveFReg:
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assert(inst.Register >= 8 && "Saved dreg must be >= 8");
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reg = inst.Register - 8;
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b = 0xDC | ((reg & 0x4) >> 2);
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streamer.emitInt8(b);
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b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
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streamer.emitInt8(b);
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break;
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case Win64EH::UOP_SaveFRegX:
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assert(inst.Register >= 8 && "Saved dreg must be >= 8");
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reg = inst.Register - 8;
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|
b = 0xDE;
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|
streamer.emitInt8(b);
|
|
b = ((reg & 0x7) << 5) | ((inst.Offset >> 3) - 1);
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_SaveFRegP:
|
|
assert(inst.Register >= 8 && "Saved dregs must be >= 8");
|
|
reg = inst.Register - 8;
|
|
b = 0xD8 | ((reg & 0x4) >> 2);
|
|
streamer.emitInt8(b);
|
|
b = ((reg & 0x3) << 6) | (inst.Offset >> 3);
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_SaveFRegPX:
|
|
assert(inst.Register >= 8 && "Saved dregs must be >= 8");
|
|
reg = inst.Register - 8;
|
|
b = 0xDA | ((reg & 0x4) >> 2);
|
|
streamer.emitInt8(b);
|
|
b = ((reg & 0x3) << 6) | ((inst.Offset >> 3) - 1);
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_End:
|
|
b = 0xE4;
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_SaveNext:
|
|
b = 0xE6;
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_TrapFrame:
|
|
b = 0xE8;
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_PushMachFrame:
|
|
b = 0xE9;
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_Context:
|
|
b = 0xEA;
|
|
streamer.emitInt8(b);
|
|
break;
|
|
case Win64EH::UOP_ClearUnwoundToCall:
|
|
b = 0xEC;
|
|
streamer.emitInt8(b);
|
|
break;
|
|
}
|
|
}
|
|
|
|
// Returns the epilog symbol of an epilog with the exact same unwind code
|
|
// sequence, if it exists. Otherwise, returns nulltpr.
|
|
// EpilogInstrs - Unwind codes for the current epilog.
|
|
// Epilogs - Epilogs that potentialy match the current epilog.
|
|
static MCSymbol*
|
|
FindMatchingEpilog(const std::vector<WinEH::Instruction>& EpilogInstrs,
|
|
const std::vector<MCSymbol *>& Epilogs,
|
|
const WinEH::FrameInfo *info) {
|
|
for (auto *EpilogStart : Epilogs) {
|
|
auto InstrsIter = info->EpilogMap.find(EpilogStart);
|
|
assert(InstrsIter != info->EpilogMap.end() &&
|
|
"Epilog not found in EpilogMap");
|
|
const auto &Instrs = InstrsIter->second;
|
|
|
|
if (Instrs.size() != EpilogInstrs.size())
|
|
continue;
|
|
|
|
bool Match = true;
|
|
for (unsigned i = 0; i < Instrs.size(); ++i)
|
|
if (Instrs[i].Operation != EpilogInstrs[i].Operation ||
|
|
Instrs[i].Offset != EpilogInstrs[i].Offset ||
|
|
Instrs[i].Register != EpilogInstrs[i].Register) {
|
|
Match = false;
|
|
break;
|
|
}
|
|
|
|
if (Match)
|
|
return EpilogStart;
|
|
}
|
|
return nullptr;
|
|
}
|
|
|
|
static void simplifyOpcodes(std::vector<WinEH::Instruction> &Instructions,
|
|
bool Reverse) {
|
|
unsigned PrevOffset = -1;
|
|
unsigned PrevRegister = -1;
|
|
|
|
auto VisitInstruction = [&](WinEH::Instruction &Inst) {
|
|
// Convert 2-byte opcodes into equivalent 1-byte ones.
|
|
if (Inst.Operation == Win64EH::UOP_SaveRegP && Inst.Register == 29) {
|
|
Inst.Operation = Win64EH::UOP_SaveFPLR;
|
|
Inst.Register = -1;
|
|
} else if (Inst.Operation == Win64EH::UOP_SaveRegPX &&
|
|
Inst.Register == 29) {
|
|
Inst.Operation = Win64EH::UOP_SaveFPLRX;
|
|
Inst.Register = -1;
|
|
} else if (Inst.Operation == Win64EH::UOP_SaveRegPX &&
|
|
Inst.Register == 19 && Inst.Offset <= 248) {
|
|
Inst.Operation = Win64EH::UOP_SaveR19R20X;
|
|
Inst.Register = -1;
|
|
} else if (Inst.Operation == Win64EH::UOP_AddFP && Inst.Offset == 0) {
|
|
Inst.Operation = Win64EH::UOP_SetFP;
|
|
} else if (Inst.Operation == Win64EH::UOP_SaveRegP &&
|
|
Inst.Register == PrevRegister + 2 &&
|
|
Inst.Offset == PrevOffset + 16) {
|
|
Inst.Operation = Win64EH::UOP_SaveNext;
|
|
Inst.Register = -1;
|
|
Inst.Offset = 0;
|
|
// Intentionally not creating UOP_SaveNext for float register pairs,
|
|
// as current versions of Windows (up to at least 20.04) is buggy
|
|
// regarding SaveNext for float pairs.
|
|
}
|
|
// Update info about the previous instruction, for detecting if
|
|
// the next one can be made a UOP_SaveNext
|
|
if (Inst.Operation == Win64EH::UOP_SaveR19R20X) {
|
|
PrevOffset = 0;
|
|
PrevRegister = 19;
|
|
} else if (Inst.Operation == Win64EH::UOP_SaveRegPX) {
|
|
PrevOffset = 0;
|
|
PrevRegister = Inst.Register;
|
|
} else if (Inst.Operation == Win64EH::UOP_SaveRegP) {
|
|
PrevOffset = Inst.Offset;
|
|
PrevRegister = Inst.Register;
|
|
} else if (Inst.Operation == Win64EH::UOP_SaveNext) {
|
|
PrevRegister += 2;
|
|
PrevOffset += 16;
|
|
} else {
|
|
PrevRegister = -1;
|
|
PrevOffset = -1;
|
|
}
|
|
};
|
|
|
|
// Iterate over instructions in a forward order (for prologues),
|
|
// backwards for epilogues (i.e. always reverse compared to how the
|
|
// opcodes are stored).
|
|
if (Reverse) {
|
|
for (auto It = Instructions.rbegin(); It != Instructions.rend(); It++)
|
|
VisitInstruction(*It);
|
|
} else {
|
|
for (WinEH::Instruction &Inst : Instructions)
|
|
VisitInstruction(Inst);
|
|
}
|
|
}
|
|
|
|
static int checkPackedEpilog(MCStreamer &streamer, WinEH::FrameInfo *info,
|
|
int PrologCodeBytes) {
|
|
// Can only pack if there's one single epilog
|
|
if (info->EpilogMap.size() != 1)
|
|
return -1;
|
|
|
|
const std::vector<WinEH::Instruction> &Epilog =
|
|
info->EpilogMap.begin()->second;
|
|
|
|
// Can pack if the epilog is a subset of the prolog but not vice versa
|
|
if (Epilog.size() > info->Instructions.size())
|
|
return -1;
|
|
|
|
// Check that the epilog actually is a perfect match for the end (backwrds)
|
|
// of the prolog.
|
|
for (int I = Epilog.size() - 1; I >= 0; I--) {
|
|
if (info->Instructions[I] != Epilog[Epilog.size() - 1 - I])
|
|
return -1;
|
|
}
|
|
|
|
// Check that the epilog actually is at the very end of the function,
|
|
// otherwise it can't be packed.
|
|
uint32_t DistanceFromEnd = (uint32_t)GetAbsDifference(
|
|
streamer, info->FuncletOrFuncEnd, info->EpilogMap.begin()->first);
|
|
if (DistanceFromEnd / 4 != Epilog.size())
|
|
return -1;
|
|
|
|
int Offset = Epilog.size() == info->Instructions.size()
|
|
? 0
|
|
: ARM64CountOfUnwindCodes(ArrayRef<WinEH::Instruction>(
|
|
&info->Instructions[Epilog.size()],
|
|
info->Instructions.size() - Epilog.size()));
|
|
|
|
// Check that the offset and prolog size fits in the first word; it's
|
|
// unclear whether the epilog count in the extension word can be taken
|
|
// as packed epilog offset.
|
|
if (Offset > 31 || PrologCodeBytes > 124)
|
|
return -1;
|
|
|
|
info->EpilogMap.clear();
|
|
return Offset;
|
|
}
|
|
|
|
static bool tryPackedUnwind(WinEH::FrameInfo *info, uint32_t FuncLength,
|
|
int PackedEpilogOffset) {
|
|
if (PackedEpilogOffset == 0) {
|
|
// Fully symmetric prolog and epilog, should be ok for packed format.
|
|
// For CR=3, the corresponding synthesized epilog actually lacks the
|
|
// SetFP opcode, but unwinding should work just fine despite that
|
|
// (if at the SetFP opcode, the unwinder considers it as part of the
|
|
// function body and just unwinds the full prolog instead).
|
|
} else if (PackedEpilogOffset == 1) {
|
|
// One single case of differences between prolog and epilog is allowed:
|
|
// The epilog can lack a single SetFP that is the last opcode in the
|
|
// prolog, for the CR=3 case.
|
|
if (info->Instructions.back().Operation != Win64EH::UOP_SetFP)
|
|
return false;
|
|
} else {
|
|
// Too much difference between prolog and epilog.
|
|
return false;
|
|
}
|
|
unsigned RegI = 0, RegF = 0;
|
|
int Predecrement = 0;
|
|
enum {
|
|
Start,
|
|
Start2,
|
|
IntRegs,
|
|
FloatRegs,
|
|
InputArgs,
|
|
StackAdjust,
|
|
FrameRecord,
|
|
End
|
|
} Location = Start;
|
|
bool StandaloneLR = false, FPLRPair = false;
|
|
int StackOffset = 0;
|
|
int Nops = 0;
|
|
// Iterate over the prolog and check that all opcodes exactly match
|
|
// the canonical order and form. A more lax check could verify that
|
|
// all saved registers are in the expected locations, but not enforce
|
|
// the order - that would work fine when unwinding from within
|
|
// functions, but not be exactly right if unwinding happens within
|
|
// prologs/epilogs.
|
|
for (const WinEH::Instruction &Inst : info->Instructions) {
|
|
switch (Inst.Operation) {
|
|
case Win64EH::UOP_End:
|
|
if (Location != Start)
|
|
return false;
|
|
Location = Start2;
|
|
break;
|
|
case Win64EH::UOP_SaveR19R20X:
|
|
if (Location != Start2)
|
|
return false;
|
|
Predecrement = Inst.Offset;
|
|
RegI = 2;
|
|
Location = IntRegs;
|
|
break;
|
|
case Win64EH::UOP_SaveRegX:
|
|
if (Location != Start2)
|
|
return false;
|
|
Predecrement = Inst.Offset;
|
|
if (Inst.Register == 19)
|
|
RegI += 1;
|
|
else if (Inst.Register == 30)
|
|
StandaloneLR = true;
|
|
else
|
|
return false;
|
|
// Odd register; can't be any further int registers.
|
|
Location = FloatRegs;
|
|
break;
|
|
case Win64EH::UOP_SaveRegPX:
|
|
// Can't have this in a canonical prologue. Either this has been
|
|
// canonicalized into SaveR19R20X or SaveFPLRX, or it's an unsupported
|
|
// register pair.
|
|
// It can't be canonicalized into SaveR19R20X if the offset is
|
|
// larger than 248 bytes, but even with the maximum case with
|
|
// RegI=10/RegF=8/CR=1/H=1, we end up with SavSZ = 216, which should
|
|
// fit into SaveR19R20X.
|
|
// The unwinding opcodes can't describe the otherwise seemingly valid
|
|
// case for RegI=1 CR=1, that would start with a
|
|
// "stp x19, lr, [sp, #-...]!" as that fits neither SaveRegPX nor
|
|
// SaveLRPair.
|
|
return false;
|
|
case Win64EH::UOP_SaveRegP:
|
|
if (Location != IntRegs || Inst.Offset != 8 * RegI ||
|
|
Inst.Register != 19 + RegI)
|
|
return false;
|
|
RegI += 2;
|
|
break;
|
|
case Win64EH::UOP_SaveReg:
|
|
if (Location != IntRegs || Inst.Offset != 8 * RegI)
|
|
return false;
|
|
if (Inst.Register == 19 + RegI)
|
|
RegI += 1;
|
|
else if (Inst.Register == 30)
|
|
StandaloneLR = true;
|
|
else
|
|
return false;
|
|
// Odd register; can't be any further int registers.
|
|
Location = FloatRegs;
|
|
break;
|
|
case Win64EH::UOP_SaveLRPair:
|
|
if (Location != IntRegs || Inst.Offset != 8 * RegI ||
|
|
Inst.Register != 19 + RegI)
|
|
return false;
|
|
RegI += 1;
|
|
StandaloneLR = true;
|
|
Location = FloatRegs;
|
|
break;
|
|
case Win64EH::UOP_SaveFRegX:
|
|
// Packed unwind can't handle prologs that only save one single
|
|
// float register.
|
|
return false;
|
|
case Win64EH::UOP_SaveFReg:
|
|
if (Location != FloatRegs || RegF == 0 || Inst.Register != 8 + RegF ||
|
|
Inst.Offset != 8 * (RegI + (StandaloneLR ? 1 : 0) + RegF))
|
|
return false;
|
|
RegF += 1;
|
|
Location = InputArgs;
|
|
break;
|
|
case Win64EH::UOP_SaveFRegPX:
|
|
if (Location != Start2 || Inst.Register != 8)
|
|
return false;
|
|
Predecrement = Inst.Offset;
|
|
RegF = 2;
|
|
Location = FloatRegs;
|
|
break;
|
|
case Win64EH::UOP_SaveFRegP:
|
|
if ((Location != IntRegs && Location != FloatRegs) ||
|
|
Inst.Register != 8 + RegF ||
|
|
Inst.Offset != 8 * (RegI + (StandaloneLR ? 1 : 0) + RegF))
|
|
return false;
|
|
RegF += 2;
|
|
Location = FloatRegs;
|
|
break;
|
|
case Win64EH::UOP_SaveNext:
|
|
if (Location == IntRegs)
|
|
RegI += 2;
|
|
else if (Location == FloatRegs)
|
|
RegF += 2;
|
|
else
|
|
return false;
|
|
break;
|
|
case Win64EH::UOP_Nop:
|
|
if (Location != IntRegs && Location != FloatRegs && Location != InputArgs)
|
|
return false;
|
|
Location = InputArgs;
|
|
Nops++;
|
|
break;
|
|
case Win64EH::UOP_AllocSmall:
|
|
case Win64EH::UOP_AllocMedium:
|
|
if (Location != Start2 && Location != IntRegs && Location != FloatRegs &&
|
|
Location != InputArgs && Location != StackAdjust)
|
|
return false;
|
|
// Can have either a single decrement, or a pair of decrements with
|
|
// 4080 and another decrement.
|
|
if (StackOffset == 0)
|
|
StackOffset = Inst.Offset;
|
|
else if (StackOffset != 4080)
|
|
return false;
|
|
else
|
|
StackOffset += Inst.Offset;
|
|
Location = StackAdjust;
|
|
break;
|
|
case Win64EH::UOP_SaveFPLRX:
|
|
// Not allowing FPLRX after StackAdjust; if a StackAdjust is used, it
|
|
// should be followed by a FPLR instead.
|
|
if (Location != Start2 && Location != IntRegs && Location != FloatRegs &&
|
|
Location != InputArgs)
|
|
return false;
|
|
StackOffset = Inst.Offset;
|
|
Location = FrameRecord;
|
|
FPLRPair = true;
|
|
break;
|
|
case Win64EH::UOP_SaveFPLR:
|
|
// This can only follow after a StackAdjust
|
|
if (Location != StackAdjust || Inst.Offset != 0)
|
|
return false;
|
|
Location = FrameRecord;
|
|
FPLRPair = true;
|
|
break;
|
|
case Win64EH::UOP_SetFP:
|
|
if (Location != FrameRecord)
|
|
return false;
|
|
Location = End;
|
|
break;
|
|
}
|
|
}
|
|
if (RegI > 10 || RegF > 8)
|
|
return false;
|
|
if (StandaloneLR && FPLRPair)
|
|
return false;
|
|
if (FPLRPair && Location != End)
|
|
return false;
|
|
if (Nops != 0 && Nops != 4)
|
|
return false;
|
|
int H = Nops == 4;
|
|
int IntSZ = 8 * RegI;
|
|
if (StandaloneLR)
|
|
IntSZ += 8;
|
|
int FpSZ = 8 * RegF; // RegF not yet decremented
|
|
int SavSZ = (IntSZ + FpSZ + 8 * 8 * H + 0xF) & ~0xF;
|
|
if (Predecrement != SavSZ)
|
|
return false;
|
|
if (FPLRPair && StackOffset < 16)
|
|
return false;
|
|
if (StackOffset % 16)
|
|
return false;
|
|
uint32_t FrameSize = (StackOffset + SavSZ) / 16;
|
|
if (FrameSize > 0x1FF)
|
|
return false;
|
|
assert(RegF != 1 && "One single float reg not allowed");
|
|
if (RegF > 0)
|
|
RegF--; // Convert from actual number of registers, to value stored
|
|
assert(FuncLength <= 0x7FF && "FuncLength should have been checked earlier");
|
|
int Flag = 0x01; // Function segments not supported yet
|
|
int CR = FPLRPair ? 3 : StandaloneLR ? 1 : 0;
|
|
info->PackedInfo |= Flag << 0;
|
|
info->PackedInfo |= (FuncLength & 0x7FF) << 2;
|
|
info->PackedInfo |= (RegF & 0x7) << 13;
|
|
info->PackedInfo |= (RegI & 0xF) << 16;
|
|
info->PackedInfo |= (H & 0x1) << 20;
|
|
info->PackedInfo |= (CR & 0x3) << 21;
|
|
info->PackedInfo |= (FrameSize & 0x1FF) << 23;
|
|
return true;
|
|
}
|
|
|
|
// Populate the .xdata section. The format of .xdata on ARM64 is documented at
|
|
// https://docs.microsoft.com/en-us/cpp/build/arm64-exception-handling
|
|
static void ARM64EmitUnwindInfo(MCStreamer &streamer, WinEH::FrameInfo *info,
|
|
bool TryPacked = true) {
|
|
// If this UNWIND_INFO already has a symbol, it's already been emitted.
|
|
if (info->Symbol)
|
|
return;
|
|
// If there's no unwind info here (not even a terminating UOP_End), the
|
|
// unwind info is considered bogus and skipped. If this was done in
|
|
// response to an explicit .seh_handlerdata, the associated trailing
|
|
// handler data is left orphaned in the xdata section.
|
|
if (info->empty()) {
|
|
info->EmitAttempted = true;
|
|
return;
|
|
}
|
|
if (info->EmitAttempted) {
|
|
// If we tried to emit unwind info before (due to an explicit
|
|
// .seh_handlerdata directive), but skipped it (because there was no
|
|
// valid information to emit at the time), and it later got valid unwind
|
|
// opcodes, we can't emit it here, because the trailing handler data
|
|
// was already emitted elsewhere in the xdata section.
|
|
streamer.getContext().reportError(
|
|
SMLoc(), "Earlier .seh_handlerdata for " + info->Function->getName() +
|
|
" skipped due to no unwind info at the time "
|
|
"(.seh_handlerdata too early?), but the function later "
|
|
"did get unwind info that can't be emitted");
|
|
return;
|
|
}
|
|
|
|
simplifyOpcodes(info->Instructions, false);
|
|
for (auto &I : info->EpilogMap)
|
|
simplifyOpcodes(I.second, true);
|
|
|
|
MCContext &context = streamer.getContext();
|
|
MCSymbol *Label = context.createTempSymbol();
|
|
|
|
streamer.emitValueToAlignment(4);
|
|
streamer.emitLabel(Label);
|
|
info->Symbol = Label;
|
|
|
|
int64_t RawFuncLength;
|
|
if (!info->FuncletOrFuncEnd) {
|
|
report_fatal_error("FuncletOrFuncEnd not set");
|
|
} else {
|
|
// FIXME: GetAbsDifference tries to compute the length of the function
|
|
// immediately, before the whole file is emitted, but in general
|
|
// that's impossible: the size in bytes of certain assembler directives
|
|
// like .align and .fill is not known until the whole file is parsed and
|
|
// relaxations are applied. Currently, GetAbsDifference fails with a fatal
|
|
// error in that case. (We mostly don't hit this because inline assembly
|
|
// specifying those directives is rare, and we don't normally try to
|
|
// align loops on AArch64.)
|
|
//
|
|
// There are two potential approaches to delaying the computation. One,
|
|
// we could emit something like ".word (endfunc-beginfunc)/4+0x10800000",
|
|
// as long as we have some conservative estimate we could use to prove
|
|
// that we don't need to split the unwind data. Emitting the constant
|
|
// is straightforward, but there's no existing code for estimating the
|
|
// size of the function.
|
|
//
|
|
// The other approach would be to use a dedicated, relaxable fragment,
|
|
// which could grow to accommodate splitting the unwind data if
|
|
// necessary. This is more straightforward, since it automatically works
|
|
// without any new infrastructure, and it's consistent with how we handle
|
|
// relaxation in other contexts. But it would require some refactoring
|
|
// to move parts of the pdata/xdata emission into the implementation of
|
|
// a fragment. We could probably continue to encode the unwind codes
|
|
// here, but we'd have to emit the pdata, the xdata header, and the
|
|
// epilogue scopes later, since they depend on whether the we need to
|
|
// split the unwind data.
|
|
RawFuncLength = GetAbsDifference(streamer, info->FuncletOrFuncEnd,
|
|
info->Begin);
|
|
}
|
|
if (RawFuncLength > 0xFFFFF)
|
|
report_fatal_error("SEH unwind data splitting not yet implemented");
|
|
uint32_t FuncLength = (uint32_t)RawFuncLength / 4;
|
|
uint32_t PrologCodeBytes = ARM64CountOfUnwindCodes(info->Instructions);
|
|
uint32_t TotalCodeBytes = PrologCodeBytes;
|
|
|
|
int PackedEpilogOffset = checkPackedEpilog(streamer, info, PrologCodeBytes);
|
|
|
|
if (PackedEpilogOffset >= 0 && !info->HandlesExceptions &&
|
|
FuncLength <= 0x7ff && TryPacked) {
|
|
// Matching prolog/epilog and no exception handlers; check if the
|
|
// prolog matches the patterns that can be described by the packed
|
|
// format.
|
|
|
|
// info->Symbol was already set even if we didn't actually write any
|
|
// unwind info there. Keep using that as indicator that this unwind
|
|
// info has been generated already.
|
|
|
|
if (tryPackedUnwind(info, FuncLength, PackedEpilogOffset))
|
|
return;
|
|
}
|
|
|
|
// Process epilogs.
|
|
MapVector<MCSymbol *, uint32_t> EpilogInfo;
|
|
// Epilogs processed so far.
|
|
std::vector<MCSymbol *> AddedEpilogs;
|
|
|
|
for (auto &I : info->EpilogMap) {
|
|
MCSymbol *EpilogStart = I.first;
|
|
auto &EpilogInstrs = I.second;
|
|
uint32_t CodeBytes = ARM64CountOfUnwindCodes(EpilogInstrs);
|
|
|
|
MCSymbol* MatchingEpilog =
|
|
FindMatchingEpilog(EpilogInstrs, AddedEpilogs, info);
|
|
if (MatchingEpilog) {
|
|
assert(EpilogInfo.find(MatchingEpilog) != EpilogInfo.end() &&
|
|
"Duplicate epilog not found");
|
|
EpilogInfo[EpilogStart] = EpilogInfo.lookup(MatchingEpilog);
|
|
// Clear the unwind codes in the EpilogMap, so that they don't get output
|
|
// in the logic below.
|
|
EpilogInstrs.clear();
|
|
} else {
|
|
EpilogInfo[EpilogStart] = TotalCodeBytes;
|
|
TotalCodeBytes += CodeBytes;
|
|
AddedEpilogs.push_back(EpilogStart);
|
|
}
|
|
}
|
|
|
|
// Code Words, Epilog count, E, X, Vers, Function Length
|
|
uint32_t row1 = 0x0;
|
|
uint32_t CodeWords = TotalCodeBytes / 4;
|
|
uint32_t CodeWordsMod = TotalCodeBytes % 4;
|
|
if (CodeWordsMod)
|
|
CodeWords++;
|
|
uint32_t EpilogCount =
|
|
PackedEpilogOffset >= 0 ? PackedEpilogOffset : info->EpilogMap.size();
|
|
bool ExtensionWord = EpilogCount > 31 || TotalCodeBytes > 124;
|
|
if (!ExtensionWord) {
|
|
row1 |= (EpilogCount & 0x1F) << 22;
|
|
row1 |= (CodeWords & 0x1F) << 27;
|
|
}
|
|
if (info->HandlesExceptions) // X
|
|
row1 |= 1 << 20;
|
|
if (PackedEpilogOffset >= 0) // E
|
|
row1 |= 1 << 21;
|
|
row1 |= FuncLength & 0x3FFFF;
|
|
streamer.emitInt32(row1);
|
|
|
|
// Extended Code Words, Extended Epilog Count
|
|
if (ExtensionWord) {
|
|
// FIXME: We should be able to split unwind info into multiple sections.
|
|
// FIXME: We should share epilog codes across epilogs, where possible,
|
|
// which would make this issue show up less frequently.
|
|
if (CodeWords > 0xFF || EpilogCount > 0xFFFF)
|
|
report_fatal_error("SEH unwind data splitting not yet implemented");
|
|
uint32_t row2 = 0x0;
|
|
row2 |= (CodeWords & 0xFF) << 16;
|
|
row2 |= (EpilogCount & 0xFFFF);
|
|
streamer.emitInt32(row2);
|
|
}
|
|
|
|
// Epilog Start Index, Epilog Start Offset
|
|
for (auto &I : EpilogInfo) {
|
|
MCSymbol *EpilogStart = I.first;
|
|
uint32_t EpilogIndex = I.second;
|
|
uint32_t EpilogOffset =
|
|
(uint32_t)GetAbsDifference(streamer, EpilogStart, info->Begin);
|
|
if (EpilogOffset)
|
|
EpilogOffset /= 4;
|
|
uint32_t row3 = EpilogOffset;
|
|
row3 |= (EpilogIndex & 0x3FF) << 22;
|
|
streamer.emitInt32(row3);
|
|
}
|
|
|
|
// Emit prolog unwind instructions (in reverse order).
|
|
uint8_t numInst = info->Instructions.size();
|
|
for (uint8_t c = 0; c < numInst; ++c) {
|
|
WinEH::Instruction inst = info->Instructions.back();
|
|
info->Instructions.pop_back();
|
|
ARM64EmitUnwindCode(streamer, info->Begin, inst);
|
|
}
|
|
|
|
// Emit epilog unwind instructions
|
|
for (auto &I : info->EpilogMap) {
|
|
auto &EpilogInstrs = I.second;
|
|
for (uint32_t i = 0; i < EpilogInstrs.size(); i++) {
|
|
WinEH::Instruction inst = EpilogInstrs[i];
|
|
ARM64EmitUnwindCode(streamer, info->Begin, inst);
|
|
}
|
|
}
|
|
|
|
int32_t BytesMod = CodeWords * 4 - TotalCodeBytes;
|
|
assert(BytesMod >= 0);
|
|
for (int i = 0; i < BytesMod; i++)
|
|
streamer.emitInt8(0xE3);
|
|
|
|
if (info->HandlesExceptions)
|
|
streamer.emitValue(
|
|
MCSymbolRefExpr::create(info->ExceptionHandler,
|
|
MCSymbolRefExpr::VK_COFF_IMGREL32, context),
|
|
4);
|
|
}
|
|
|
|
static void ARM64EmitRuntimeFunction(MCStreamer &streamer,
|
|
const WinEH::FrameInfo *info) {
|
|
MCContext &context = streamer.getContext();
|
|
|
|
streamer.emitValueToAlignment(4);
|
|
EmitSymbolRefWithOfs(streamer, info->Function, info->Begin);
|
|
if (info->PackedInfo)
|
|
streamer.emitInt32(info->PackedInfo);
|
|
else
|
|
streamer.emitValue(
|
|
MCSymbolRefExpr::create(info->Symbol, MCSymbolRefExpr::VK_COFF_IMGREL32,
|
|
context),
|
|
4);
|
|
}
|
|
|
|
void llvm::Win64EH::ARM64UnwindEmitter::Emit(MCStreamer &Streamer) const {
|
|
// Emit the unwind info structs first.
|
|
for (const auto &CFI : Streamer.getWinFrameInfos()) {
|
|
WinEH::FrameInfo *Info = CFI.get();
|
|
if (Info->empty())
|
|
continue;
|
|
MCSection *XData = Streamer.getAssociatedXDataSection(CFI->TextSection);
|
|
Streamer.SwitchSection(XData);
|
|
ARM64EmitUnwindInfo(Streamer, Info);
|
|
}
|
|
|
|
// Now emit RUNTIME_FUNCTION entries.
|
|
for (const auto &CFI : Streamer.getWinFrameInfos()) {
|
|
WinEH::FrameInfo *Info = CFI.get();
|
|
// ARM64EmitUnwindInfo above clears the info struct, so we can't check
|
|
// empty here. But if a Symbol is set, we should create the corresponding
|
|
// pdata entry.
|
|
if (!Info->Symbol)
|
|
continue;
|
|
MCSection *PData = Streamer.getAssociatedPDataSection(CFI->TextSection);
|
|
Streamer.SwitchSection(PData);
|
|
ARM64EmitRuntimeFunction(Streamer, Info);
|
|
}
|
|
}
|
|
|
|
void llvm::Win64EH::ARM64UnwindEmitter::EmitUnwindInfo(MCStreamer &Streamer,
|
|
WinEH::FrameInfo *info,
|
|
bool HandlerData) const {
|
|
// Called if there's an .seh_handlerdata directive before the end of the
|
|
// function. This forces writing the xdata record already here - and
|
|
// in this case, the function isn't actually ended already, but the xdata
|
|
// record needs to know the function length. In these cases, if the funclet
|
|
// end hasn't been marked yet, the xdata function length won't cover the
|
|
// whole function, only up to this point.
|
|
if (!info->FuncletOrFuncEnd) {
|
|
Streamer.SwitchSection(info->TextSection);
|
|
info->FuncletOrFuncEnd = Streamer.emitCFILabel();
|
|
}
|
|
// Switch sections (the static function above is meant to be called from
|
|
// here and from Emit().
|
|
MCSection *XData = Streamer.getAssociatedXDataSection(info->TextSection);
|
|
Streamer.SwitchSection(XData);
|
|
ARM64EmitUnwindInfo(Streamer, info, /* TryPacked = */ !HandlerData);
|
|
}
|