cpu-o3: Update numWays references to support per-table

[CJ362ff]

Change-Id: Ieda3140c914857d771b53248b3670a2d97cef87c

Summary by CodeRabbit

• Refactor

  • Optimized branch predictor table capacity calculations for improved efficiency
  • Streamlined internal parameter structure declarations

• Tests

  • Updated branch predictor test suite to reflect internal implementation changes

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR contains formatting and logic refinements to the BTBTAGE branch predictor. Parameter declarations are reformatted to single-line format in BranchPredictor.py, table capacity computation is updated to use indexed array access in btb_tage_ub.cc, and test utilities are updated to use direct array indexing instead of accessor functions.

Changes

Cohort / File(s)	Summary
Parameter Declaration Formatting src/cpu/pred/BranchPredictor.py	Three public VectorParam.Unsigned parameters (tableSizes, histLengths, numWays) reformatted from multiline to single-line declarations. Default values and types remain unchanged.
Predictor Logic Updates src/cpu/pred/btb/btb_tage_ub.cc	Updated table capacity calculation in initUpperBoundState to use indexed numWays[i] instead of scalar access; enhanced TagePrediction constructor calls to include finalProviderTable and finalProviderIsAlt parameters.
Test Utility Refactoring src/cpu/pred/btb/test/btb_tage.test.cc	Replaced getNumWays(t) accessor calls with direct array access to numWays[t] across multiple test functions and loop bounds.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~28 minutes

Possibly related PRs

• Revert "cpu-o3: Refactor numWays to support per-table configuration" #795: Related through BTBTAGE numWays declaration modifications in the same parameter file.
• cpu-o3: Refactor numWays to support per-table configuration #793: Related through simultaneous updates to BTBTAGE parameter declarations (tableSizes, histLengths, numWays).
• bpu,configs: Add optional BTBTAGE upper-bound mode for kmhv3 #770: Related through BTBTAGEUpperBound implementation changes affecting table capacity and prediction metadata handling.

Suggested labels

align-kmhv3

Suggested reviewers

• jensen-yan

Poem

🐰 With whiskers twitched, this rabbit hops with glee,
Array indices bounce—no more getNumWays(), you see!
Parameters line up, formatting so neat,
Predictions flow faster, the refactor complete! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the primary change: updating numWays references to support per-table configuration, which is reflected in the code changes across the three modified files.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch tage1-table-tuning-align

📝 Coding Plan

• Generate coding plan for human review comments

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[coderabbitai]

🧹 Nitpick comments (1)

src/cpu/pred/btb/test/btb_tage.test.cc (1)

235-235: Keep getNumWays() (or add explicit bounds asserts) for loop bounds in tests.

Direct tage->numWays[t] indexing drops the table-index bounds assertion provided by getNumWays(t), so a misconfigured numWays vector can become undefined access instead of a clear test failure. Please either keep getNumWays(t) here or add ASSERT_LT(t, tage->numWays.size()) before indexing.

Also applies to: 264-264, 800-800, 816-816, 828-828, 834-834, 838-838, 858-858

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/cpu/pred/btb/test/btb_tage.test.cc` at line 235, The test currently
indexes tage->numWays[t] directly which bypasses the bounds check provided by
getNumWays(t); change the loop to use tage->getNumWays(t) for bounds (or, if you
prefer direct access, add an assertion like ASSERT_LT(t, tage->numWays.size())
before any indexing) so misconfigured numWays produces a clear test failure;
update the occurrences around the loops that reference numWays (e.g., where you
currently have for (unsigned way = 0; way < tage->numWays[t]; way++)) to use
getNumWays(t) or add the explicit ASSERT_LT check.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/cpu/pred/btb/test/btb_tage.test.cc`:
- Line 235: The test currently indexes tage->numWays[t] directly which bypasses
the bounds check provided by getNumWays(t); change the loop to use
tage->getNumWays(t) for bounds (or, if you prefer direct access, add an
assertion like ASSERT_LT(t, tage->numWays.size()) before any indexing) so
misconfigured numWays produces a clear test failure; update the occurrences
around the loops that reference numWays (e.g., where you currently have for
(unsigned way = 0; way < tage->numWays[t]; way++)) to use getNumWays(t) or add
the explicit ASSERT_LT check.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 66a36b4c-3a01-42a3-b5e5-50dcd5f684d7

📥 Commits

Reviewing files that changed from the base of the PR and between 6b87b99 and 1d6095b.

📒 Files selected for processing (3)

• src/cpu/pred/BranchPredictor.py
• src/cpu/pred/btb/btb_tage_ub.cc
• src/cpu/pred/btb/test/btb_tage.test.cc