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[lldb][AArch64] Simplify handing of scalable registers using vg and svg #70914

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Nov 2, 2023
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[lldb][AArch64] Simplify handing of scalable registers using vg and svg #70914

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17 changes: 5 additions & 12 deletions lldb/source/Plugins/Process/gdb-remote/GDBRemoteRegisterContext.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -434,11 +434,6 @@ bool GDBRemoteRegisterContext::WriteRegisterBytes(const RegisterInfo *reg_info,
} else {
// This is an actual register, write it
success = SetPrimordialRegister(reg_info, gdb_comm);

if (success && do_reconfigure_arm64_sve) {
AArch64Reconfigure();
InvalidateAllRegisters();
}
}

// Check if writing this register will invalidate any other register
Expand All @@ -452,6 +447,11 @@ bool GDBRemoteRegisterContext::WriteRegisterBytes(const RegisterInfo *reg_info,
false);
}

if (success && do_reconfigure_arm64_sve) {
AArch64Reconfigure();
InvalidateAllRegisters();
}

return success;
}
} else {
Expand Down Expand Up @@ -772,8 +772,6 @@ void GDBRemoteRegisterContext::AArch64Reconfigure() {
std::optional<uint64_t> vg_reg_value;
const RegisterInfo *vg_reg_info = m_reg_info_sp->GetRegisterInfo("vg");
if (vg_reg_info) {
// Make sure we get the latest value of vg from the remote.
SetRegisterIsValid(vg_reg_info, false);
uint32_t vg_reg_num = vg_reg_info->kinds[eRegisterKindLLDB];
uint64_t reg_value = ReadRegisterAsUnsigned(vg_reg_num, fail_value);
if (reg_value != fail_value && reg_value <= 32)
Expand All @@ -783,11 +781,6 @@ void GDBRemoteRegisterContext::AArch64Reconfigure() {
std::optional<uint64_t> svg_reg_value;
const RegisterInfo *svg_reg_info = m_reg_info_sp->GetRegisterInfo("svg");
if (svg_reg_info) {
// When vg is written it is automatically made invalid. Writing vg will also
// change svg if we're in streaming mode but it will not be made invalid
// so do this manually so the following read gets the latest svg value.
SetRegisterIsValid(svg_reg_info, false);

uint32_t svg_reg_num = svg_reg_info->kinds[eRegisterKindLLDB];
uint64_t reg_value = ReadRegisterAsUnsigned(svg_reg_num, fail_value);
if (reg_value != fail_value && reg_value <= 32)
Expand Down
55 changes: 37 additions & 18 deletions lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
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Expand Up @@ -1612,6 +1612,22 @@ bool ProcessGDBRemote::CalculateThreadStopInfo(ThreadGDBRemote *thread) {
return false;
}

void ProcessGDBRemote::ParseExpeditedRegisters(
ExpeditedRegisterMap &expedited_register_map, ThreadSP thread_sp) {
ThreadGDBRemote *gdb_thread = static_cast<ThreadGDBRemote *>(thread_sp.get());
RegisterContextSP gdb_reg_ctx_sp(gdb_thread->GetRegisterContext());

for (const auto &pair : expedited_register_map) {
StringExtractor reg_value_extractor(pair.second);
WritableDataBufferSP buffer_sp(
new DataBufferHeap(reg_value_extractor.GetStringRef().size() / 2, 0));
reg_value_extractor.GetHexBytes(buffer_sp->GetData(), '\xcc');
uint32_t lldb_regnum = gdb_reg_ctx_sp->ConvertRegisterKindToRegisterNumber(
eRegisterKindProcessPlugin, pair.first);
gdb_thread->PrivateSetRegisterValue(lldb_regnum, buffer_sp->GetData());
}
}

ThreadSP ProcessGDBRemote::SetThreadStopInfo(
lldb::tid_t tid, ExpeditedRegisterMap &expedited_register_map,
uint8_t signo, const std::string &thread_name, const std::string &reason,
Expand Down Expand Up @@ -1646,32 +1662,35 @@ ThreadSP ProcessGDBRemote::SetThreadStopInfo(

reg_ctx_sp->InvalidateIfNeeded(true);

auto iter = std::find(m_thread_ids.begin(), m_thread_ids.end(), tid);
if (iter != m_thread_ids.end())
SetThreadPc(thread_sp, iter - m_thread_ids.begin());

ParseExpeditedRegisters(expedited_register_map, thread_sp);

// AArch64 SVE/SME specific code below updates SVE and ZA register sizes and
// offsets if value of VG or SVG registers has changed since last stop.
const ArchSpec &arch = GetTarget().GetArchitecture();
if (arch.IsValid() && arch.GetTriple().isAArch64()) {
GDBRemoteRegisterContext *gdb_remote_reg_ctx =
static_cast<GDBRemoteRegisterContext *>(reg_ctx_sp.get());
GDBRemoteRegisterContext *reg_ctx_sp =
static_cast<GDBRemoteRegisterContext *>(
gdb_thread->GetRegisterContext().get());

if (gdb_remote_reg_ctx) {
gdb_remote_reg_ctx->AArch64Reconfigure();
gdb_remote_reg_ctx->InvalidateAllRegisters();
if (reg_ctx_sp) {
reg_ctx_sp->AArch64Reconfigure();
// Now we have changed the offsets of all the registers, so the values
// will be corrupted.
reg_ctx_sp->InvalidateAllRegisters();

// Expedited registers values will never contain registers that would be
// resized by AArch64Reconfigure. So we are safe to continue using these
// values. These values include vg, svg and useful general purpose
// registers so this saves a few read packets each time we make use of
// them.
ParseExpeditedRegisters(expedited_register_map, thread_sp);
}
}

auto iter = std::find(m_thread_ids.begin(), m_thread_ids.end(), tid);
if (iter != m_thread_ids.end())
SetThreadPc(thread_sp, iter - m_thread_ids.begin());

for (const auto &pair : expedited_register_map) {
StringExtractor reg_value_extractor(pair.second);
WritableDataBufferSP buffer_sp(
new DataBufferHeap(reg_value_extractor.GetStringRef().size() / 2, 0));
reg_value_extractor.GetHexBytes(buffer_sp->GetData(), '\xcc');
uint32_t lldb_regnum = reg_ctx_sp->ConvertRegisterKindToRegisterNumber(
eRegisterKindProcessPlugin, pair.first);
gdb_thread->PrivateSetRegisterValue(lldb_regnum, buffer_sp->GetData());
}
thread_sp->SetName(thread_name.empty() ? nullptr : thread_name.c_str());

gdb_thread->SetThreadDispatchQAddr(thread_dispatch_qaddr);
Expand Down
3 changes: 3 additions & 0 deletions lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.h
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Expand Up @@ -470,6 +470,9 @@ class ProcessGDBRemote : public Process,
void DidForkSwitchSoftwareBreakpoints(bool enable);
void DidForkSwitchHardwareTraps(bool enable);

void ParseExpeditedRegisters(ExpeditedRegisterMap &expedited_register_map,
lldb::ThreadSP thread_sp);

// Lists of register fields generated from the remote's target XML.
// Pointers to these RegisterFlags will be set in the register info passed
// back to the upper levels of lldb. Doing so is safe because this class will
Expand Down
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