Pair tage no abtb utage by Yakkhini · Pull Request #849 · OpenXiangShan/GEM5

Yakkhini · 2026-05-06T08:05:35Z

No description provided.

Change-Id: If2cc05e51438056fbff8494f01a8d7ec5563fa08

Change-Id: I38e4f40c32115620ffb17855cbe4d1e7844757a0

Change-Id: Ic30d22dcd05328c3f6b36c15649907ce1de7c3f1

Change-Id: I2fbd20dcaf9d0619f17e205d75c86ca2263b63fc

Change-Id: I9d25427c5fbc6158354956d65c83b09973fbaf26

Change-Id: I6f67bb179ffbb5393decb3be230c606002a92b29

Change-Id: Icd33b74fcee3758ab577542462bf9c697f8bb8ca

Change-Id: Ibb07242c6bfb0a0e7a8c6c8671a7ebfd63aee352

Change-Id: If438a5151de40e8297f64e31950091b2e286ca3c

Change-Id: I9150455b296244736f06bb4ea6cc0e061a4bf2c7

Change-Id: I32413da228d2e0f933d7dfac61e212fece5f72ce

Change-Id: Ifeb2071764ee1ac7a106989073289585f96b8e35

Change-Id: I6791517c2f2af8bfab8da7daa917cd2d77642b6f

Change-Id: I0b16e47e4d43e7cbf97f4d846231f4483fe20294

Keep the existing provider entry when a mismatching update can be allocated into a higher table, and only update provider metadata when the first block still matches. Change-Id: Ic7bfad527bfec1e0f234fd4ec879fdd8f97862e5

Break the previous second-block first-block-overridden bucket into no-candidate, fall-through mismatch, control-address mismatch, and target mismatch so the full-mode failure path can be diagnosed without conflating missing candidates with true overrides. Change-Id: Ic5f69d0c7199a04fb3187feaa3beec0ec2969846

Break PairTAGE first-block training failures into coverage buckets, and split second-block no-first-block-candidate skips into lookup-miss versus untrainable-first-block cases so coverage gaps can be diagnosed without conflating them with table misses. Change-Id: Idc02576b3fbbd19821de86a25c256c964f44e951

Change-Id: I8e40f3ac5e2b1aa2502947b18eecd3fc4e920609

Change-Id: Ieadee72421a58ab9d6b3313ffe0509ae573dd304

Change-Id: I8d5f177e995d6b831bc61831d91cf5ad62f3effe

Change-Id: I0be57a509489d4b7a0948ddffa73b726ab73b4aa

Change-Id: I3ca49428560409c0aadf8c0fda144488c5cad335

Change-Id: Ie564817f298ff85e0d4f2d06a3e8d6c47e18899e

Change-Id: I05c0cdd0685cb9e2b3cbe261a8a0780f17eba7f6

coderabbitai · 2026-05-06T08:05:43Z

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Change-Id: I63b8dab9ff60323a74ecea570cc1970dd0f2203e

github-actions · 2026-05-06T08:42:03Z

🚀 Coremark Smoke Test Results

Branch	IPC	Change
Base (`xs-dev`)	`2.3130`	-
This PR	`2.1579`	📉 `-0.1551` (`-6.71%`)

✅ Difftest smoke test passed!

Change-Id: Ib124277cb25cd90e4a2d75ed089c18fbe1e56db2

Change-Id: I0aa0122de316356e918b7002710c3a44921ede35

Change-Id: I41b06527d820ae092c0985e94f769df2fb161f1a

github-actions · 2026-05-07T14:40:51Z

🚀 Coremark Smoke Test Results

Branch	IPC	Change
Base (`xs-dev`)	`2.3130`	-
This PR	`2.2947`	📉 `-0.0184` (`-0.79%`)

✅ Difftest smoke test passed!

github-actions · 2026-05-07T14:45:14Z

🚀 Performance test triggered: gcc15-spec06-0.8c

XiangShanRobot · 2026-05-07T16:51:18Z

[Generated by GEM5 Performance Robot]
commit: 8888f99
workflow: On-Demand SPEC Test (Tier 1.5)

Ideal BTB Performance

Overall Score

	PR	Master	Diff(%)
Score	21.62	21.54	+0.37 🟢

[Generated by GEM5 Performance Robot]
commit: 8888f99
workflow: On-Demand SPEC Test (Tier 1.5)

Ideal BTB Performance

Overall Score

	PR	Previous Commit	Diff(%)
Score	21.62	22.13	-2.30 🔴

XiangShanRobot · 2026-05-07T16:51:36Z

[Generated by GEM5 Performance Robot]
commit: 8888f99
workflow: On-Demand SPEC Test (Tier 1.5)

Ideal BTB Performance

Overall Score

	PR	Master	Diff(%)
Score	21.62	21.54	+0.37 🟢

[Generated by GEM5 Performance Robot]
commit: 8888f99
workflow: On-Demand SPEC Test (Tier 1.5)

Ideal BTB Performance

Overall Score

	PR	Previous Commit	Diff(%)
Score	21.62	22.13	-2.30 🔴

Yakkhini added 24 commits May 6, 2026 14:57

cpu: add pair tage framework

9a94506

Change-Id: If2cc05e51438056fbff8494f01a8d7ec5563fa08

cpu: process second entry

6b9423a

Change-Id: I38e4f40c32115620ffb17855cbe4d1e7844757a0

cpu: train first block in pair tage

06a03cf

Change-Id: Ic30d22dcd05328c3f6b36c15649907ce1de7c3f1

cpu: fix initialization order of pairtage to avoid assertion fail

8d8cc88

Change-Id: I2fbd20dcaf9d0619f17e205d75c86ca2263b63fc

cpu: train second block in pair tage

ee23fe7

Change-Id: I9d25427c5fbc6158354956d65c83b09973fbaf26

cpu: enqueue second block

c091c14

Change-Id: I6f67bb179ffbb5393decb3be230c606002a92b29

cpu: not handle second block when first block has been override

fad2676

Change-Id: Icd33b74fcee3758ab577542462bf9c697f8bb8ca

cpu: cast and store metas in second block

479070e

Change-Id: Ibb07242c6bfb0a0e7a8c6c8671a7ebfd63aee352

cpu: do not enqueue second block when it disagreed

cc934aa

Change-Id: If438a5151de40e8297f64e31950091b2e286ca3c

cpu: add parity to distinguish 1st 2nd block phase in pair tage

03cef63

Change-Id: I9150455b296244736f06bb4ea6cc0e061a4bf2c7

cpu: add pairtage entry branch pc range check

3c6734e

Change-Id: I32413da228d2e0f933d7dfac61e212fece5f72ce

cpu: Add PairTAGE observability counters

0ac58d3

Change-Id: Ifeb2071764ee1ac7a106989073289585f96b8e35

cpu: Add PairTAGE first-only mode

2c76d5e

Change-Id: I6791517c2f2af8bfab8da7daa917cd2d77642b6f

cpu: Allocate PairTAGE entries toward higher tables

8b0e661

Change-Id: I0b16e47e4d43e7cbf97f4d846231f4483fe20294

cpu: Preserve PairTAGE providers on mismatch

07b9566

Keep the existing provider entry when a mismatching update can be allocated into a higher table, and only update provider metadata when the first block still matches. Change-Id: Ic7bfad527bfec1e0f234fd4ec879fdd8f97862e5

cpu: Add PairTAGE fallthrough-first-block support

46f6f2f

Change-Id: I8e40f3ac5e2b1aa2502947b18eecd3fc4e920609

cpu: Increase default PairTAGE capacity to 8x

8245277

Change-Id: Ieadee72421a58ab9d6b3313ffe0509ae573dd304

cpu: enable standalone fallthrough train by default

90ee3b1

Change-Id: I8d5f177e995d6b831bc61831d91cf5ad62f3effe

cpu: Enable PairTAGE odd-phase operation

916cd6a

Change-Id: I0be57a509489d4b7a0948ddffa73b726ab73b4aa

cpu: Increase default PairTAGE capacity to 32x

c12c7e9

Change-Id: I3ca49428560409c0aadf8c0fda144488c5cad335

cpu: support typed first-block pairtage training

807f3b5

Change-Id: Ie564817f298ff85e0d4f2d06a3e8d6c47e18899e

cpu: increase default pairtage table capacity

4c742a1

Change-Id: I05c0cdd0685cb9e2b3cbe261a8a0780f17eba7f6

cpu: fix unexpected PHist update multiple times in same cycle

b62cf3b

Change-Id: I63b8dab9ff60323a74ecea570cc1970dd0f2203e

Yakkhini added 2 commits May 7, 2026 16:17

cpu: Preserve PairTAGE second-block context

c8c0c3e

Change-Id: Ib124277cb25cd90e4a2d75ed089c18fbe1e56db2

cpu: Age PairTAGE provider identity

4126e7b

Change-Id: I0aa0122de316356e918b7002710c3a44921ede35

Yakkhini force-pushed the pair-tage-no-abtb-utage branch from bbe7f74 to 8cb695e Compare May 7, 2026 13:27

Yakkhini force-pushed the pair-tage-no-abtb-utage branch from 8cb695e to 8888f99 Compare May 7, 2026 14:31

cpu: Use PairTAGE first-block only

8888f99

Change-Id: I41b06527d820ae092c0985e94f769df2fb161f1a

Yakkhini added the perf label May 7, 2026

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Pair tage no abtb utage#849

Pair tage no abtb utage#849
Yakkhini wants to merge 28 commits into
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Yakkhini commented May 6, 2026

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Yakkhini commented May 6, 2026

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🚀 Coremark Smoke Test Results

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🚀 Coremark Smoke Test Results

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XiangShanRobot commented May 7, 2026

Ideal BTB Performance

Overall Score

Ideal BTB Performance

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XiangShanRobot commented May 7, 2026

Ideal BTB Performance

Overall Score

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coderabbitai Bot commented May 6, 2026 •

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