feat: add breakpoint instruction

This commit introduces `breakpoint`, a transparent issue that will
cause a debug execution to break when reached.

This instruction will not be serialized into libraries, and will not
have an opcode or be part of the code block tree.

For debug executions, it will produce a `NOOP`, so the internal clock of
the VM will be affected.

The decision of not including this as part of the code block is to avoid
further consuming variants of opcodes as they are already scarce.

related issue: #580

assembly/src/assembler/context.rs

@@ -250,11 +250,17 @@ impl AssemblyContext {
     // HELPER METHODS
     // --------------------------------------------------------------------------------------------
 
-    /// Returns the context of the procedure currently being complied, or None if module or
+    /// Returns the context of the procedure currently being compiled, or None if module or
     /// procedure stacks are empty.
     fn current_proc_context(&self) -> Option<&ProcedureContext> {
         self.module_stack.last().and_then(|m| m.proc_stack.last())
     }
+
+    /// Returns the name of the procedure currently being compilied, or None if module or
+    /// procedure stacks are empty.
+    pub(crate) fn current_proc_context_name(&self) -> Option<&str> {
+        self.current_proc_context().map(|p| p.name().as_ref())
+    }
 }
 
 // MODULE CONTEXT
@@ -478,6 +484,10 @@ impl ProcedureContext {
         self.name.is_main()
     }
 
+    pub const fn name(&self) -> &ProcedureName {
+        &self.name
+    }
+
     pub fn into_procedure(self, id: ProcedureId, code_root: CodeBlock) -> Procedure {
         let Self {
             name,

assembly/src/assembler/instruction/mod.rs

@@ -34,7 +34,7 @@ impl Assembler {
         // this will allow us to map the instruction to the sequence of operations which were
         // executed as a part of this instruction.
         if self.in_debug_mode() {
-            span.track_instruction(instruction);
+            span.track_instruction(instruction, ctx);
         }
 
         let result = match instruction {
@@ -306,6 +306,15 @@ impl Assembler {
             Instruction::CallLocal(idx) => self.call_local(*idx, ctx),
             Instruction::CallImported(id) => self.call_imported(id, ctx),
             Instruction::SysCall(id) => self.syscall(id, ctx),
+
+            // ----- debug decorators -------------------------------------------------------------
+            Instruction::Breakpoint => {
+                if self.in_debug_mode() {
+                    span.add_op(Noop)?;
+                    span.track_instruction(instruction, ctx);
+                }
+                Ok(None)
+            }
         };
 
         // compute and update the cycle count of the instruction which just finished executing

assembly/src/assembler/span_builder.rs

@@ -1,6 +1,6 @@
 use super::{
-    AssemblyError, BodyWrapper, Borrow, CodeBlock, Decorator, DecoratorList, Instruction,
-    Operation, ToString, Vec,
+    AssemblyContext, AssemblyError, BodyWrapper, Borrow, CodeBlock, Decorator, DecoratorList,
+    Instruction, Operation, ToString, Vec,
 };
 use vm_core::AssemblyOp;
 
@@ -102,8 +102,11 @@ impl SpanBuilder {
     ///
     /// This indicates that the provided instruction should be tracked and the cycle count for
     /// this instruction will be computed when the call to set_instruction_cycle_count() is made.
-    pub fn track_instruction(&mut self, instruction: &Instruction) {
-        let op = AssemblyOp::new(instruction.to_string(), 0);
+    pub fn track_instruction(&mut self, instruction: &Instruction, ctx: &mut AssemblyContext) {
+        let proc = ctx.current_proc_context_name().unwrap_or("#main");
+        let op = instruction.to_string();
+        let op = format!("{proc}:{op}");
+        let op = AssemblyOp::new(op, 0);
         self.push_decorator(Decorator::AsmOp(op));
         self.last_asmop_pos = self.decorators.len() - 1;
     }

assembly/src/lib.rs

@@ -24,7 +24,7 @@ pub use procedures::{ProcedureId, ProcedureName};
 
 mod parsers;
 use parsers::PROCEDURE_LABEL_PARSER;
-pub use parsers::{parse_module, parse_program, ModuleAst, ProcedureAst, ProgramAst};
+pub use parsers::{parse_module, parse_program, Instruction, ModuleAst, ProcedureAst, ProgramAst};
 
 mod serde;
 pub use serde::{ByteReader, ByteWriter, Deserializable, Serializable};

assembly/src/parsers/context.rs

@@ -511,6 +511,9 @@ impl ParserContext {
             // ----- constant statements ----------------------------------------------------------
             "const" => Err(ParsingError::const_invalid_scope(op)),
 
+            // ----- debug decorators -------------------------------------------------------------
+            "breakpoint" => simple_instruction(op, Breakpoint),
+
             // ----- catch all --------------------------------------------------------------------
             _ => Err(ParsingError::invalid_op(op)),
         }

assembly/src/parsers/mod.rs

@@ -7,7 +7,8 @@ use core::{fmt::Display, ops::RangeBounds};
 
 mod nodes;
 use crate::utils::bound_into_included_u64;
-pub(crate) use nodes::{Instruction, Node};
+pub use nodes::Instruction;
+pub(crate) use nodes::Node;
 mod context;
 use context::ParserContext;
 mod labels;

assembly/src/parsers/nodes.rs

@@ -277,6 +277,9 @@ pub enum Instruction {
     CallLocal(u16),
     CallImported(ProcedureId),
     SysCall(ProcedureId),
+
+    // ----- debug decorators ---------------------------------------------------------------------
+    Breakpoint,
 }
 
 impl fmt::Display for Instruction {
@@ -543,6 +546,9 @@ impl fmt::Display for Instruction {
             Self::CallLocal(index) => write!(f, "call.{index}"),
             Self::CallImported(proc_id) => write!(f, "call.{proc_id}"),
             Self::SysCall(proc_id) => write!(f, "syscall.{proc_id}"),
+
+            // ----- debug decorators -------------------------------------------------------------
+            Self::Breakpoint => write!(f, "breakpoint"),
         }
     }
 }

assembly/src/parsers/serde/serialization.rs

@@ -467,6 +467,11 @@ impl Serializable for Instruction {
                 OpCode::SysCall.write_into(target)?;
                 imported.write_into(target)?
             }
+
+            // ----- debug decorators -------------------------------------------------------------
+            Self::Breakpoint => {
+                // this is a transparent instruction and will not be encoded into the library
+            }
         }
         Ok(())
     }

miden/src/cli/debug/executor.rs

@@ -45,6 +45,9 @@ impl DebugExecutor {
             DebugCommand::Continue => {
                 while let Some(new_vm_state) = self.next_vm_state() {
                     self.vm_state = new_vm_state;
+                    if self.should_break() {
+                        break;
+                    }
                 }
                 self.print_vm_state();
             }
@@ -53,6 +56,9 @@ impl DebugExecutor {
                     match self.next_vm_state() {
                         Some(next_vm_state) => {
                             self.vm_state = next_vm_state;
+                            if self.should_break() {
+                                break;
+                            }
                         }
                         None => break,
                     }
@@ -70,6 +76,9 @@ impl DebugExecutor {
                     match self.prev_vm_state() {
                         Some(new_vm_state) => {
                             self.vm_state = new_vm_state;
+                            if self.should_break() {
+                                break;
+                            }
                         }
                         None => break,
                     }
@@ -213,4 +222,9 @@ impl DebugExecutor {
 
         println!("{}", message);
     }
+
+    /// Returns `true` if the current state should break.
+    fn should_break(&self) -> bool {
+        self.vm_state.asmop.as_ref().map(|asm| asm.should_break()).unwrap_or(false)
+    }
 }

processor/Cargo.toml

@@ -23,12 +23,12 @@ std = ["vm-core/std", "winter-prover/std", "log/std"]
 
 [dependencies]
 log = "0.4.14"
+assembly = { package = "miden-assembly", path = "../assembly", version = "0.5", default-features = false }
 vm-core = { package = "miden-core", path = "../core", version = "0.5", default-features = false }
 winter-prover = { package = "winter-prover", version = "0.5", default-features = false }
 
 [dev-dependencies]
 logtest = { version = "2.0", default-features = false  }
-miden-assembly = { package = "miden-assembly", path = "../assembly", version = "0.5", default-features = false }
 rand-utils = { package = "winter-rand-utils", version = "0.5" }
 winter-fri = { package = "winter-fri", version = "0.5" }
 winter-utils = { package = "winter-utils", version = "0.5" }

processor/src/debug.rs

@@ -1,6 +1,6 @@
 use crate::{
-    advice::AdviceProvider, Chiplets, Decoder, ExecutionError, Felt, Process, Stack, StarkField,
-    System, Vec,
+    advice::AdviceProvider, Chiplets, Decoder, ExecutionError, Felt, Instruction, Process, Stack,
+    StarkField, System, Vec,
 };
 use core::fmt;
 use vm_core::{utils::string::String, Operation, StackOutputs, Word};
@@ -24,8 +24,17 @@ impl fmt::Display for VmState {
             self.memory.iter().map(|x| (x.0, word_to_ints(&x.1))).collect();
         write!(
             f,
-            "clk={}, op={:?}, asmop={:?}, fmp={}, stack={stack:?}, memory={memory:?}",
-            self.clk, self.op, self.asmop, self.fmp
+            "clk={}{}{}, fmp={}, stack={stack:?}, memory={memory:?}",
+            self.clk,
+            match self.op {
+                Some(op) => format!(", op={op}"),
+                None => "".to_string(),
+            },
+            match &self.asmop {
+                Some(op) => format!(", {op}"),
+                None => "".to_string(),
+            },
+            self.fmp
         )
     }
 }
@@ -87,7 +96,7 @@ impl VmStateIterator {
             (
                 &assembly_ops[self.asmop_idx - 1],
                 // difference between current clock cycle and start clock cycle of the current asmop
-                (self.clk - assembly_ops[self.asmop_idx - 1].0 as u32) as u8,
+                (self.clk as i32 - assembly_ops[self.asmop_idx - 1].0 as i32) as i8,
             )
         } else {
             (next_asmop, 0) //dummy value, never used.
@@ -106,7 +115,7 @@ impl VmStateIterator {
         // if this is not the first asmop in the list and if this op is part of current asmop,
         // returns a new instance of [AsmOp] instantiated with current asmop, num_cycles and
         // cycle_idx of current op.
-        else if self.asmop_idx > 0 && cycle_idx <= curr_asmop.1.num_cycles() {
+        else if self.asmop_idx > 0 && cycle_idx <= curr_asmop.1.num_cycles() as i8 {
             let asmop = Some(AsmOpInfo::new(
                 curr_asmop.1.op().clone(),
                 curr_asmop.1.num_cycles(),
@@ -222,7 +231,8 @@ fn word_to_ints(word: &Word) -> [u64; 4] {
 pub struct AsmOpInfo {
     op: String,
     num_cycles: u8,
-    cycle_idx: u8,
+    cycle_idx: i8,
+    should_break: bool,
 }
 
 // ASMOP STATE
@@ -232,11 +242,19 @@ impl AsmOpInfo {
     /// Returns [AsmOpInfo] instantiated with the specified assembly instruction string, number of
     /// cycles it takes to execute the assembly instruction and op index in sequence of operations
     /// corresponding to the current assembly instruction. The first index is 1 instead of 0.
-    pub fn new(op: String, num_cycles: u8, cycle_idx: u8) -> Self {
+    pub fn new(op: String, num_cycles: u8, cycle_idx: i8) -> Self {
+        // breakpoint doesn't exist as operation. we instead assume the properly formatted
+        // decorator will carry this data
+        let should_break = op
+            .split(':')
+            .last()
+            .filter(|l| l == &Instruction::Breakpoint.to_string().as_str())
+            .is_some();
         Self {
             op,
             num_cycles,
             cycle_idx,
+            should_break,
         }
     }
 
@@ -263,7 +281,18 @@ impl AsmOpInfo {
 
     /// Returns the operation index of the operation at the specified clock cycle in the sequence
     /// of operations corresponding to the current assembly instruction.
-    pub fn cycle_idx(&self) -> u8 {
+    pub fn cycle_idx(&self) -> i8 {
         self.cycle_idx
     }
+
+    /// Returns `true` if the debug should break for this line.
+    pub const fn should_break(&self) -> bool {
+        self.should_break
+    }
+}
+
+impl fmt::Display for AsmOpInfo {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "decorator={}, cost={}, cycles={}", self.op, self.num_cycles, self.cycle_idx)
+    }
 }

processor/src/lib.rs

@@ -4,6 +4,7 @@
 #[macro_use]
 extern crate alloc;
 
+use assembly::Instruction;
 pub use vm_core::{
     chiplets::hasher::Digest,
     crypto::{