Function StoreStateToPackedECContext

Source/Windows/ARM64EC/Module.cpp:460–526

Reconstructs an x64 context from the input thread's state, packed into a regular ARM64 context following the ARM64EC register mapping

// Reconstructs an x64 context from the input thread's state, packed into a regular ARM64 context following the ARM64EC register mapping
static ARM64_NT_CONTEXT StoreStateToPackedECContext(FEXCore::Core::InternalThreadState* Thread, uint32_t FPCR, uint32_t FPSR) {
  ARM64_NT_CONTEXT ECContext {};

  ECContext.ContextFlags = CONTEXT_ARM64_FULL;
  if (CPUFeatures->IsFeaturePresent(PF_AVX2_INSTRUCTIONS_AVAILABLE)) {
    // This is a FEX extension and requires corresponding wine-side patches to be of use, however it is harmless to set
    // even if those patches are not used.
    ECContext.ContextFlags |= CONTEXT_ARM64_FEX_YMMSTATE;
  }

  auto& State = Thread->CurrentFrame->State;

  ECContext.X8 = State.gregs[FEXCore::X86State::REG_RAX];
  ECContext.X0 = State.gregs[FEXCore::X86State::REG_RCX];
  ECContext.X1 = State.gregs[FEXCore::X86State::REG_RDX];
  ECContext.X27 = State.gregs[FEXCore::X86State::REG_RBX];
  ECContext.Sp = State.gregs[FEXCore::X86State::REG_RSP];
  ECContext.Fp = State.gregs[FEXCore::X86State::REG_RBP];
  ECContext.X25 = State.gregs[FEXCore::X86State::REG_RSI];
  ECContext.X26 = State.gregs[FEXCore::X86State::REG_RDI];
  ECContext.X2 = State.gregs[FEXCore::X86State::REG_R8];
  ECContext.X3 = State.gregs[FEXCore::X86State::REG_R9];
  ECContext.X4 = State.gregs[FEXCore::X86State::REG_R10];
  ECContext.X5 = State.gregs[FEXCore::X86State::REG_R11];
  ECContext.X19 = State.gregs[FEXCore::X86State::REG_R12];
  ECContext.X20 = State.gregs[FEXCore::X86State::REG_R13];
  ECContext.X21 = State.gregs[FEXCore::X86State::REG_R14];
  ECContext.X22 = State.gregs[FEXCore::X86State::REG_R15];

  ECContext.Pc = State.rip;

  CTX->ReconstructXMMRegisters(Thread, reinterpret_cast<__uint128_t*>(&ECContext.V[0]), reinterpret_cast<__uint128_t*>(&ECContext.V[16]));

  ECContext.Lr = State.mm[0][0];
  ECContext.X6 = State.mm[1][0];
  ECContext.X7 = State.mm[2][0];
  ECContext.X9 = State.mm[3][0];
  ECContext.X16 = (State.mm[3][1] & 0xffff) << 48 | (State.mm[2][1] & 0xffff) << 32 | (State.mm[1][1] & 0xffff) << 16 | (State.mm[0][1] & 0xffff);
  ECContext.X10 = State.mm[4][0];
  ECContext.X11 = State.mm[5][0];
  ECContext.X12 = State.mm[6][0];
  ECContext.X15 = State.mm[7][0];
  ECContext.X17 = (State.mm[7][1] & 0xffff) << 48 | (State.mm[6][1] & 0xffff) << 32 | (State.mm[5][1] & 0xffff) << 16 | (State.mm[4][1] & 0xffff);

  // Zero all disallowed registers
  ECContext.X13 = 0;
  ECContext.X14 = 0;
  ECContext.X18 = 0;
  ECContext.X23 = 0;
  ECContext.X24 = 0;
  ECContext.X28 = 0;

  // NZCV+SS will be converted into EFlags by ntdll, the rest are lost during exception handling.
  // See HandleGuestException
  uint32_t EFlags = CTX->ReconstructCompactedEFLAGS(Thread, false, nullptr, 0);
  ECContext.Cpsr = 0;
  ECContext.Cpsr |= (EFlags & (1U << FEXCore::X86State::RFLAG_TF_RAW_LOC)) ? (1U << 21) : 0;
  ECContext.Cpsr |= (EFlags & (1U << FEXCore::X86State::RFLAG_OF_RAW_LOC)) ? (1U << 28) : 0;