[WIP] cpu: Save selective oracle replay experiment

[jensen-yan]

Summary

This draft PR saves the current selective BPU oracle replay experiment for later continuation.

The patch adds CSV record/replay parameters alongside the existing DB replay path:

• selectiveOracleRecordCSVFile
• selectiveOracleReplayCSVFile

CSV replay parses the old logical fetch-block format and feeds the existing filtered global replay stream instead of using a per-startPC FIFO. This preserves the useful short-window behavior for the mcf hot branch experiment while keeping the DB code path in place.

Status

This is experimental and not ready to merge as-is.

The short mcf check confirms that per-startPC FIFO was one source of bad alignment:

• mcf_6388 1.5M, bad FIFO: 0x1088c = 7083/30511
• mcf_6388 1.5M, CSV global replay: 0x1088c = 1309/30511, TraceMissing = 1

The full 40M check still does not recover the earlier stitched prototype:

• current CSV global replay: total IPC 0.493201, condMiss 610605, recovery 39759344
• old stitched prototype: total IPC 0.504425, condMiss 516465, recovery 34001448
• current CSV global replay has large second-window drift: TraceMissing = 988164

So the remaining issue is replay cursor drift over long runs, not CSV vs DB storage itself.

Validation

• git diff --check
• scons build/RISCV/gem5.opt --gold-linker -j64
• mcf_6388 1.5M CSV replay using /tmp/bpu_oracle_mcf_6388_record_dual/selective_oracle_blocks.csv
• mcf_6388 40M CSV replay using the same CSV
• coremark 200K CSV record smoke: generated 27736 blocks and 38063 outcomes

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🚀 Coremark Smoke Test Results

Branch	IPC	Change
Base (xs-dev)	2.3168	-
This PR	2.3168	➡️ 0.0000 (0.00%)

✅ Difftest smoke test passed!