# Phase 75-5: PGO Regeneration (C5/C6 Inline Slots Aware) — Next Instructions

**Status**: NEXT (HIGH PRIORITY)

## Goal

Rebuild the FAST PGO SSOT binary (`bench_random_mixed_hakmem_minimal_pgo`) with a training profile that matches the **current promoted defaults**:
- `HAKMEM_WARM_POOL_SIZE=16`
- `HAKMEM_TINY_C5_INLINE_SLOTS=1`
- `HAKMEM_TINY_C6_INLINE_SLOTS=1`

This is required because Phase 75-4 observed a large gap between:
- **Phase 69 historical FAST baseline** (62.63M ops/s)
- **Phase 75-4 current FAST PGO Point A baseline** (53.81M ops/s)

## SSOT Rules

- Use `scripts/run_mixed_10_cleanenv.sh` as the harness.
- Always pin the binary explicitly via `BENCH_BIN=...` to avoid Standard/FAST confusion.
- Keep comparisons within the **same binary** when judging a single knob (C5/C6 OFF/ON).

## Step 1: Prepare training commands (C5/C6 ON)

Pick one of these approaches (A is preferred):

### A) Training uses the harness (preferred)

Ensure the training workload exports the correct knobs:

```bash
export HAKMEM_WARM_POOL_SIZE=16
export HAKMEM_TINY_C5_INLINE_SLOTS=1
export HAKMEM_TINY_C6_INLINE_SLOTS=1
```

Then run the existing PGO training target (repo-specific; example):

```bash
make pgo-fast-full
```

### B) Hard-pin knobs inside PGO training config (if needed)

If the training driver does not inherit ENV cleanly, update the PGO training config script to include:
- `HAKMEM_WARM_POOL_SIZE=16`
- `HAKMEM_TINY_C5_INLINE_SLOTS=1`
- `HAKMEM_TINY_C6_INLINE_SLOTS=1`

## Step 2: Validate the rebuilt binary

Run Mixed SSOT 10-run on FAST PGO:

```bash
BENCH_BIN=./bench_random_mixed_hakmem_minimal_pgo scripts/run_mixed_10_cleanenv.sh
```

Record mean/median/CV and update the scorecard baseline if improved.

## Step 3: Re-run Phase 75-4 matrix on FAST PGO (sanity)

Run 4-point matrix on FAST PGO to confirm:
- Point D > Point A
- and quantify additivity (B/C contributions)

```bash
BENCH_BIN=./bench_random_mixed_hakmem_minimal_pgo \
  HAKMEM_TINY_C5_INLINE_SLOTS=0 HAKMEM_TINY_C6_INLINE_SLOTS=0 RUNS=10 \
  scripts/run_mixed_10_cleanenv.sh

BENCH_BIN=./bench_random_mixed_hakmem_minimal_pgo \
  HAKMEM_TINY_C5_INLINE_SLOTS=1 HAKMEM_TINY_C6_INLINE_SLOTS=0 RUNS=10 \
  scripts/run_mixed_10_cleanenv.sh

BENCH_BIN=./bench_random_mixed_hakmem_minimal_pgo \
  HAKMEM_TINY_C5_INLINE_SLOTS=0 HAKMEM_TINY_C6_INLINE_SLOTS=1 RUNS=10 \
  scripts/run_mixed_10_cleanenv.sh

BENCH_BIN=./bench_random_mixed_hakmem_minimal_pgo \
  HAKMEM_TINY_C5_INLINE_SLOTS=1 HAKMEM_TINY_C6_INLINE_SLOTS=1 RUNS=10 \
  scripts/run_mixed_10_cleanenv.sh
```

## Step 4: If regression persists, do layout tax forensics

Use:

```bash
./scripts/box/layout_tax_forensics_box.sh \
  ./bench_random_mixed_hakmem_minimal_pgo_phase69_best \
  ./bench_random_mixed_hakmem_minimal_pgo
```

Then classify:
- IPC drop (>3%) → text layout / inlining / code placement issue
- branch-miss spike (>10%) → hint mismatch / control-flow reshaping
- cache/dTLB spike → data layout / TLS bloat / spill

## GO/NO-GO Gates

- **GO**: FAST PGO baseline recovers significantly (target: close to Phase 69 order-of-magnitude), and Phase 75-4 D vs A remains ≥ +1.0%.
- **NEUTRAL**: D vs A stays positive but baseline still low → keep investigating training config.
- **NO-GO**: D vs A becomes negative → revert or rework inline slots integration for FAST builds.