vulkan: fix output corruption on GCN 2.0/3.0 (Vulkan 1.2)#21787
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rafikb wants to merge 1 commit intoggml-org:masterfrom
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vulkan: fix output corruption on GCN 2.0/3.0 (Vulkan 1.2)#21787rafikb wants to merge 1 commit intoggml-org:masterfrom
rafikb wants to merge 1 commit intoggml-org:masterfrom
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Overview
This PR resolves output corruption (token repetition/double-wording) on legacy AMD GCN 2.0 and 3.0 hardware (e.g., R9 390, Fury X).
The issue was introduced in b8394 due to the implementation of modern Vulkan synchronization primitives that are not fully supported by the final legacy Adrenalin drivers (Vulkan 1.2.170). By restoring backward-compatible memory barrier logic in ggml-vulkan.cpp, we restore coherent generation for these cards without regressing performance on modern Vulkan 1.3+ hardware.
Additional information
Hardware Tested: Radeon R9 390 (8GB VRAM) on Windows 10.
Performance: Verified 22.0 t/s using gemma-4-E4B-it-Q4_K_M.gguf with 100% GPU offload.
Context: Many legacy 8GB cards are still highly capable for inference in 2026, but are limited by driver-level Vulkan support. This fix ensures continued accessibility for users on vintage or budget-restricted hardware.
Requirements