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refactor: narrow dwarf direct materialization #152

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Merged
swananan merged 1 commit into from
May 4, 2026
Merged

refactor: narrow dwarf direct materialization #152

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106 changes: 67 additions & 39 deletions ghostscope-compiler/src/ebpf/dwarf_bridge.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -77,15 +77,71 @@ impl<'ctx, 'dw> EbpfContext<'ctx, 'dw> {
);
debug!("Evaluation context PC address: 0x{:x}", pc_address);

let pt_regs_ptr = self.get_pt_regs_parameter()?;
let result_size = MemoryAccessSize::from_size(Self::get_dwarf_type_size(dwarf_type));
if let Some(value) = ghostscope_dwarf::PlannedValue::from_location(location.clone()) {
return self
.planned_value_to_llvm_value(&value, dwarf_type, var_name, pc_address, status_ptr);
}

match location {
VariableLocation::RegisterValue { dwarf_reg } => {
VariableLocation::AbsoluteAddressValue(_)
| VariableLocation::RegisterValue { .. }
| VariableLocation::ComputedValue(_)
| VariableLocation::ImplicitValue(_) => Err(CodeGenError::DwarfError(format!(
"Direct DWARF value '{var_name}' could not be materialized as a planned value"
))),
VariableLocation::Address(_)
| VariableLocation::RegisterAddress { .. }
| VariableLocation::ComputedAddress(_) => {
self.generate_memory_location(location, dwarf_type, status_ptr)
}
VariableLocation::OptimizedOut => {
debug!("Variable {} is optimized out", var_name);
Err(Self::dwarf_expression_unavailable_error(
var_name,
&Availability::OptimizedOut,
pc_address,
))
}
VariableLocation::Pieces(pieces) => {
debug!(
"Variable {} is composite with {} pieces",
var_name,
pieces.len()
);
Err(CodeGenError::DwarfError(format!(
"DWARF variable '{var_name}' is split across pieces; piece reconstruction is not implemented"
)))
}
VariableLocation::FrameBaseRelative { .. } => Err(CodeGenError::DwarfError(
"Frame-base-relative variable plan requires resolved frame base".to_string(),
)),
VariableLocation::Unknown => Err(CodeGenError::DwarfError(
"Variable read plan has unknown location".to_string(),
)),
}
}

fn planned_value_to_llvm_value(
&mut self,
value: &ghostscope_dwarf::PlannedValue,
dwarf_type: &TypeInfo,
var_name: &str,
_pc_address: u64,
status_ptr: Option<PointerValue<'ctx>>,
) -> Result<BasicValueEnum<'ctx>> {
let pt_regs_ptr = self.get_pt_regs_parameter()?;
let result_size = MemoryAccessSize::from_size(Self::get_dwarf_type_size(dwarf_type));
match value {
ghostscope_dwarf::PlannedValue::Constant(value) => Ok(self
.context
.i64_type()
.const_int(*value as u64, true)
.into()),
ghostscope_dwarf::PlannedValue::RegisterValue { dwarf_reg } => {
debug!("Generating register value: {dwarf_reg}");
self.load_register_value(*dwarf_reg, pt_regs_ptr)
}
VariableLocation::ComputedValue(steps) => {
ghostscope_dwarf::PlannedValue::ComputedValue { steps } => {
debug!("Generating computed value: {} steps", steps.len());
let runtime_status_ptr = if self.condition_context_active {
Some(self.get_or_create_cond_error_global())
Expand All @@ -100,52 +156,24 @@ impl<'ctx, 'dw> EbpfContext<'ctx, 'dw> {
None,
)
}
VariableLocation::ImplicitValue(bytes) => {
ghostscope_dwarf::PlannedValue::ImplicitBytes(bytes) => {
debug!("Generating implicit value: {} bytes", bytes.len());
let mut value: u64 = 0;
for (i, &byte) in bytes.iter().enumerate().take(8) {
value |= (byte as u64) << (i * 8);
}
Ok(self.context.i64_type().const_int(value, false).into())
}
VariableLocation::AbsoluteAddressValue(_) => {
ghostscope_dwarf::PlannedValue::AddressValue { address } => {
debug!("Generating address direct value for variable: {var_name}");
let runtime_status_ptr = if self.condition_context_active {
Some(self.get_or_create_cond_error_global())
} else {
status_ptr
};
self.variable_location_to_address_with_hint(location, runtime_status_ptr, None)
self.planned_address_to_llvm_address(address, runtime_status_ptr, None)
.map(Into::into)
}
VariableLocation::Address(_)
| VariableLocation::RegisterAddress { .. }
| VariableLocation::ComputedAddress(_) => {
self.generate_memory_location(location, dwarf_type, status_ptr)
}
VariableLocation::OptimizedOut => {
debug!("Variable {} is optimized out", var_name);
Err(Self::dwarf_expression_unavailable_error(
var_name,
&Availability::OptimizedOut,
pc_address,
))
}
VariableLocation::Pieces(pieces) => {
debug!(
"Variable {} is composite with {} pieces",
var_name,
pieces.len()
);
Err(CodeGenError::DwarfError(format!(
"DWARF variable '{var_name}' is split across pieces; piece reconstruction is not implemented"
)))
}
VariableLocation::FrameBaseRelative { .. } => Err(CodeGenError::DwarfError(
"Frame-base-relative variable plan requires resolved frame base".to_string(),
)),
VariableLocation::Unknown => Err(CodeGenError::DwarfError(
"Variable read plan has unknown location".to_string(),
)),
}
}

Expand Down Expand Up @@ -453,14 +481,14 @@ impl<'ctx, 'dw> EbpfContext<'ctx, 'dw> {
status_ptr: Option<PointerValue<'ctx>>,
) -> Result<BasicValueEnum<'ctx>> {
match &materialization.materialization {
ghostscope_dwarf::VariableMaterialization::DirectValue { location, .. } => {
ghostscope_dwarf::VariableMaterialization::DirectValue { value } => {
let dwarf_type = materialization.dwarf_type.as_ref().ok_or_else(|| {
CodeGenError::DwarfError(
"Expression has no DWARF type information".to_string(),
)
})?;
self.variable_location_to_llvm_value(
location,
self.planned_value_to_llvm_value(
value,
dwarf_type,
&materialization.name,
pc_address,
Expand Down
2 changes: 1 addition & 1 deletion ghostscope-dwarf/src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ pub use core::{
// Re-export semantic contract types.
pub use semantics::{
AddressOrigin, AddressSpaceInfo, CfaRulePlan, CompactUnwindRow, CompactUnwindStats,
CompactUnwindTable, InlineFrame, PcContext, PcLineInfo, PcRange, PlannedAddress,
CompactUnwindTable, InlineFrame, PcContext, PcLineInfo, PcRange, PlannedAddress, PlannedValue,
RegisterRecoveryPlan, UnwindDiagnostic, UnwindDiagnosticKind, VariableAccessPath,
VariableAccessSegment, VariableLoweringKind, VariableLoweringPlan, VariableMaterialization,
VariableMaterializationPlan, VariablePlan, VariableQueryDiagnostic, VariableReadPlan,
Expand Down
128 changes: 96 additions & 32 deletions ghostscope-dwarf/src/semantics/variable_plan.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -73,21 +73,21 @@ pub struct PlannedAddress {
pub origin: AddressOrigin,
}

#[derive(Debug, Clone, PartialEq)]
pub enum PlannedValue {
Constant(i64),
RegisterValue { dwarf_reg: u16 },
ComputedValue { steps: Vec<ComputeStep> },
ImplicitBytes(Vec<u8>),
AddressValue { address: PlannedAddress },
}

#[derive(Debug, Clone, PartialEq)]
pub enum VariableMaterialization {
DirectValue {
location: VariableLocation,
address_origin: Option<AddressOrigin>,
},
UserMemoryRead {
address: PlannedAddress,
},
Composite {
pieces: Vec<PieceLocation>,
},
Unavailable {
availability: Availability,
},
DirectValue { value: PlannedValue },
UserMemoryRead { address: PlannedAddress },
Composite { pieces: Vec<PieceLocation> },
Unavailable { availability: Availability },
}

#[derive(Debug, Clone, PartialEq)]
Expand Down Expand Up @@ -288,10 +288,21 @@ impl VariableReadPlan {
}
} else {
match lowering.kind {
VariableLoweringKind::DirectValue => VariableMaterialization::DirectValue {
address_origin: direct_value_address_origin(&self.location),
location: self.location.clone(),
},
VariableLoweringKind::DirectValue => {
match PlannedValue::from_location(self.location.clone()) {
Some(value) => VariableMaterialization::DirectValue { value },
None => VariableMaterialization::Unavailable {
availability: Availability::Unsupported(
UnsupportedReason::ExpressionShape {
detail: format!(
"location {} cannot be materialized as a direct value",
self.location
),
},
),
},
}
}
VariableLoweringKind::UserMemoryRead => {
match PlannedAddress::from_location(self.location.clone()) {
Some(address) => VariableMaterialization::UserMemoryRead { address },
Expand Down Expand Up @@ -450,6 +461,35 @@ impl VariableReadPlan {
}
}

impl PlannedValue {
pub fn from_location(location: VariableLocation) -> Option<Self> {
match location {
VariableLocation::RegisterValue { dwarf_reg } => {
Some(Self::RegisterValue { dwarf_reg })
}
VariableLocation::ComputedValue(steps) => {
if let [ComputeStep::PushConstant(value)] = steps.as_slice() {
Some(Self::Constant(*value))
} else {
Some(Self::ComputedValue { steps })
}
}
VariableLocation::ImplicitValue(bytes) => Some(Self::ImplicitBytes(bytes)),
VariableLocation::AbsoluteAddressValue(expr) => {
PlannedAddress::from_location(VariableLocation::AbsoluteAddressValue(expr))
.map(|address| Self::AddressValue { address })
}
VariableLocation::Address(_)
| VariableLocation::RegisterAddress { .. }
| VariableLocation::FrameBaseRelative { .. }
| VariableLocation::ComputedAddress(_)
| VariableLocation::Pieces(_)
| VariableLocation::OptimizedOut
| VariableLocation::Unknown => None,
}
}
}

impl PlannedAddress {
pub fn from_location(location: VariableLocation) -> Option<Self> {
let origin = match &location {
Expand Down Expand Up @@ -512,13 +552,6 @@ impl RuntimeCapabilities {
}
}

fn direct_value_address_origin(location: &VariableLocation) -> Option<AddressOrigin> {
match location {
VariableLocation::AbsoluteAddressValue(expr) => Some(address_origin_for_steps(&expr.steps)),
_ => None,
}
}

fn address_origin_for_steps(steps: &[ComputeStep]) -> AddressOrigin {
if fold_constant_steps(steps).is_some() {
return AddressOrigin::LinkTime;
Expand Down Expand Up @@ -1140,19 +1173,50 @@ mod tests {

match materialized.materialization {
VariableMaterialization::DirectValue {
address_origin,
location,
} => {
assert_eq!(address_origin, Some(AddressOrigin::LinkTime));
assert!(matches!(
location,
VariableLocation::AbsoluteAddressValue(_)
));
value:
PlannedValue::AddressValue {
address:
PlannedAddress {
origin: AddressOrigin::LinkTime,
..
},
},
} => {}
VariableMaterialization::DirectValue { value } => {
panic!("unexpected direct value: {value:?}");
}
other => panic!("unexpected materialization: {other:?}"),
}
}

#[test]
fn materialization_plan_converts_constant_direct_value() {
let plan = read_plan(VariableLocation::ComputedValue(vec![
ComputeStep::PushConstant(42),
]));
let materialized = plan.materialization_plan(&capabilities(false));

match materialized.materialization {
VariableMaterialization::DirectValue {
value: PlannedValue::Constant(42),
} => {}
other => panic!("unexpected materialization: {other:?}"),
}
}

#[test]
fn materialization_plan_converts_register_direct_value() {
let plan = read_plan(VariableLocation::RegisterValue { dwarf_reg: 6 });
let materialized = plan.materialization_plan(&capabilities(false));

match materialized.materialization {
VariableMaterialization::DirectValue {
value: PlannedValue::RegisterValue { dwarf_reg: 6 },
} => {}
other => panic!("unexpected materialization: {other:?}"),
}
}

#[test]
fn materialization_plan_surfaces_piece_locations_without_first_piece_fallback() {
let plan = read_plan(VariableLocation::Pieces(vec![PieceLocation {
Expand Down
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