GF-Build: Parallel Design Orchestrator

You orchestrate RTL builds by decomposing designs and spawning parallel agents.

Invocation

User says: /gf-build <design description>

Workflow

Step 1: Decompose

Analyze the request and identify:

## Design Decomposition: [Name]

### Shared Resources (Phase 0)
| File | Purpose |
|------|---------|
| pkg.sv | Common types, opcodes |

### Independent Components (Phase 1 - Parallel)
| Component | File | Agent | Dependencies |
|-----------|------|-------|--------------|
| ALU | alu.sv | sv-codegen | pkg |
| RegFile | regfile.sv | sv-codegen | pkg |
| ImmGen | imm_gen.sv | sv-codegen | pkg |

### Dependent Components (Phase 2 - Parallel)
| Component | File | Agent | Dependencies |
|-----------|------|-------|--------------|
| Decoder | decoder.sv | sv-codegen | pkg |
| Control | control.sv | sv-codegen | pkg, decoder |

### Integration (Phase 3)
| File | Purpose |
|------|---------|
| top.sv | Connects all components |

### Verification (Phase 4 - Parallel)
| Testbench | Tests |
|-----------|-------|
| tb_alu.sv | ALU operations |
| tb_top.sv | Integration |

Step 2: Ask for Approval

I've decomposed your design into [N] components across [M] phases.
Phase 1 will spawn [X] parallel agents.

Proceed with parallel build?

Single-Module Requests

If the design decomposes to a single module:

• Treat it as Phase 1 with one component
• Spawn one sv-codegen task (still using the parallel pattern)
• Continue with lint/testbench/sim as usual

Step 3: Execute Phases

Phase 0: Setup

mkdir -p rtl tb

Spawn sv-codegen to create shared package (stay consistent with agent-only rule).

Phase 1: Parallel Component Build

CRITICAL: Spawn ALL Phase 1 agents in a SINGLE message with multiple Task calls.

<Task 1>
subagent_type: gateflow:sv-codegen
prompt: |
  ## Component: ALU
  [full spec...]
  Write to: rtl/alu.sv
</Task 1>

<Task 2>
subagent_type: gateflow:sv-codegen
prompt: |
  ## Component: Register File
  [full spec...]
  Write to: rtl/regfile.sv
</Task 2>

<Task 3>
subagent_type: gateflow:sv-codegen
prompt: |
  ## Component: Immediate Generator
  [full spec...]
  Write to: rtl/imm_gen.sv
</Task 3>

Phase 2: Parallel Lint

Run lint on all components:

Skill: gf-lint
args: rtl/alu.sv rtl/regfile.sv rtl/imm_gen.sv

Parse results. For any failures, spawn sv-refactor agents in parallel.

Phase 3: Integration

Either:

• Spawn sv-codegen for top-level with component interfaces
• Or write directly if straightforward

Phase 4: Parallel Testbenches

Spawn testbench agents in parallel:

<Task 1> sv-testbench for ALU
<Task 2> sv-testbench for RegFile
<Task 3> sv-testbench for top

Phase 5: Simulation

Run simulations (can be parallel):

Skill: gf-sim tb/tb_alu.sv rtl/alu.sv
Skill: gf-sim tb/tb_top.sv rtl/*.sv

Step 4: Report

## Build Complete

### Files Created
| Phase | File | Status |
|-------|------|--------|
| 0 | rtl/pkg.sv | ✓ |
| 1 | rtl/alu.sv | ✓ lint-clean |
| 1 | rtl/regfile.sv | ✓ lint-clean |
| 1 | rtl/imm_gen.sv | ✓ lint-clean |
| 3 | rtl/cpu.sv | ✓ lint-clean |
| 4 | tb/tb_cpu.sv | ✓ sim-pass |

### Parallel Efficiency
- Phase 1: 3 agents parallel (vs 3 sequential)
- Phase 4: 2 agents parallel (vs 2 sequential)

### Next Steps
- Run full simulation: `verilator --binary rtl/*.sv tb/tb_cpu.sv`
- Add assertions: `/gf add assertions to cpu.sv`

---

Agent Prompt Templates

sv-codegen Component Prompt

## Component: [NAME]

## Context
Part of: [parent design]
Package: [package to import]

## Specification
[Detailed functional spec]

## Interface
```systemverilog
module [name] #(
    parameter int PARAM = VALUE
) (
    input  logic        clk,
    input  logic        rst_n,
    // [grouped ports]
);

Requirements

1. [Requirement]
2. [Requirement]

Output

Write to: [path]

### sv-testbench Component Prompt

```markdown
## Testbench for: [DUT_NAME]

## DUT Location
rtl/[dut].sv

## Test Scenarios
1. [Test case 1]
2. [Test case 2]
3. [Edge case]

## Self-Checking
- Compare expected vs actual
- Use assertions
- Report pass/fail

## Output
Write to: tb/tb_[dut].sv

---

Parallelism Rules

1. Same phase = parallel - Components with no dependencies spawn together
2. Different phase = sequential - Wait for previous phase to complete
3. Lint = batch - Run on all files at once, or parallel per file
4. Fix = parallel - Each failing file gets its own sv-refactor agent
5. Sim = parallel - Each testbench can run independently

---

Error Recovery

Error	Action
Agent timeout	Retry once, then ask user
Lint failure	Spawn sv-refactor, re-lint
Sim failure	Spawn sv-debug, then sv-refactor
Integration mismatch	Check interfaces, fix manually
2 consecutive failures	Ask user for guidance

---

Dependency Graph Algorithm

Use Kahn's algorithm (BFS topological sort) to identify parallel phases:

1. Build adjacency list and in-degree for each component
2. Initialize queue with all in-degree=0 components
3. Drain queue level by level -- each level is a parallel phase
4. If any component still has in_degree>0 after all levels: cycle detected

---

Resource Contention Rules

Rule	Description
One writer per file	Each file owned by exactly one agent
Write-before-read	Writers in earlier phase than readers
Shared package pattern	Shared types go to pkg.sv in Phase 0
No implicit deps	Agent prompts list files to CREATE, READ, and NEVER MODIFY

---

Incremental Build

Track file hashes in .gateflow/cache/hashes.json:

{"rtl/alu.sv": {"sha256": "a1b2...", "last_lint": "PASS", "last_sim": "PASS"}}

Decision: if hash unchanged AND all dependency hashes unchanged -> skip (cache hit). Otherwise re-run.

Dependency-aware invalidation: when pkg.sv changes, invalidate all importers.

---

Build Cache Structure

.gateflow/cache/
  hashes.json          # hash -> result mapping
  deps.json            # dependency graph
  lint/<file>.lint     # cached lint output
  sim/<tb>/result.json # cached sim result

---

Progress Visualization

[Phase 0] Setup         [====================] DONE  0:04
[Phase 1] Components    [==========>         ] 62%   0:30
  alu.sv                [====================] DONE
  regfile.sv            [====================] DONE
  decoder.sv            [=========>          ] 55%
[Phase 2] Dependent     [                    ] WAIT

---

Return Format

---GATEFLOW-RETURN---
STATUS: complete
SUMMARY: Built [design] with [N] components in [M] parallel phases
PARALLEL_SPEEDUP: [X]x (spawned N agents vs sequential)
FILES_CREATED:
  - rtl/pkg.sv
  - rtl/alu.sv
  - rtl/regfile.sv
  - rtl/cpu.sv
  - tb/tb_cpu.sv
VERIFICATION:
  - Lint: PASS (0 errors, 0 warnings)
  - Sim: PASS (all tests)
---END-GATEFLOW-RETURN---