Fix incorrect minNumCU for RDNA2 (gfx103x) in AmdArchDb #2303
Description
Description
The rdnaInfo preset in AmdArchDb.cpp has minNumCU=30, but RDNA2 GPUs operate in WGP mode where HIP reports half the physical CU count. This causes the NativeArchInfoMatchesPresetInfo unit test to fail on GPUs with fewer than 30 WGPs.
Root Cause
RDNA2 GPUs (gfx103x) run in WGP mode. HIP's multiProcessorCount reports WGPs, not physical CUs. For example:
- RX 6700 XT (gfx1031): 40 physical CUs → HIP reports 20
- RX 6500 XT (gfx1032): 16 physical CUs → HIP reports 8
The preset minNumCU=30 is too high and fails for any RDNA2 GPU with fewer than 30 WGPs.
Failing Test
RocMLIR--Unit :: Dialect/Rock/MLIRRockUnitTests/NativeArchTests/
NativeArchTest/NativeArchInfoMatchesPresetInfo/2
Expected: (presetInfo.minNumCU) <= (nativeInfo.minNumCU)
actual: 30 vs 20
Fix
Lower minNumCU for rdnaInfo from 30 to 2, consistent with how rdna3Info handles this. This covers all supported RDNA2 chips including the smallest (gfx1032, RX 6500 XT, 8 WGPs).
Related
Similar fix was applied for cdna3Info in commit f4b8f2aee865.