Flattening and remove ifelse adds instructions with empty call stacks
Closed this issue · 0 comments
Aim
Profiling where all the constraints in the program come from
Expected Behavior
Every ACIR opcode should have a call stack associated with it
Bug
Some ACIR opcodes in the program have no call stack associated. I've added a condition in the SSA printer to figure out wich instructions in SSA do not have any call stack associated.
I've tracked down these instructions to some optimization steps:
flatten_cfg.rs
: Explicitely usesCallStack::new()
for instructions related with the if condition. A solution to this might be to add call_stack to JmpIf in the same way Jmp and Return have call stacks, to associated the emitted instructions with.value_merger.rs::merge_numeric_values
: This seems to be emitting some Cast and mul instructions with no call stack associated, because sometimes the if value and the else value have no call stack associated. I guess this can happen when the if else values don't come from previous instructions, such as being block params or constantsremove_if_else.rs
: Seems to be emitting array_get instructions with no call_stack, presumably fromvalue_merger::merge_array_values
that has a explicitCallStack::new()
when emitting an ArrayGet
In the case we can't track down the instructions to a specific location instruction, it'd be good to at least use the call stack of the function being processed, allowing users to at least track that the instruction comes from a given function call, even though they might not know which part of the function being called generated it 🤔
To Reproduce
Modify this code in printer.rs
/// Display an arbitrary instruction
pub(crate) fn display_instruction(
function: &Function,
instruction: InstructionId,
f: &mut Formatter,
) -> Result {
// instructions are always indented within a function
write!(f, " ")?;
let results = function.dfg.instruction_results(instruction);
if !results.is_empty() {
write!(f, "{} = ", value_list(function, results))?;
}
display_instruction_inner(function, &function.dfg[instruction], f, instruction)
}
fn display_instruction_inner(
function: &Function,
instruction: &Instruction,
f: &mut Formatter,
instruction_id: InstructionId,
) -> Result {
let show = |id| value(function, id);
let call_stack = function.dfg.get_call_stack(instruction_id);
if call_stack.is_empty() {
write!(f, "NO CALL STACK ")?;
}
And compile a large program such as aztec protocol circuits or the token contract transfer function with show ssa enabled.
Project Impact
None
Impact Context
No response
Workaround
None
Workaround Description
No response
Additional Context
No response
Installation Method
None
Nargo Version
No response
NoirJS Version
No response
Would you like to submit a PR for this Issue?
None
Support Needs
No response