[llvm] [AMDGPU] Using feature to define vmem cacheline size (PR #207884)

[Robert Imschweiler via llvm-commits]

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@@ -197,6 +200,9 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   /// Instruction cache line size in bytes (64 for pre-GFX11, 128 for GFX11+).
   unsigned getInstCacheLineSize() const { return InstCacheLineSize; }
 
+  /// Data (VMEM) cache line size in bytes (128 by default, 256 for GFX12.6+).
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ro-i wrote:

you neither set 128 as the default, nor 256 for GFX12.6+?

https://github.com/llvm/llvm-project/pull/207884