[llvm] [AMDGPU] Exclude gfx1251 (w/ FullRate64Ops) from using GFX1250VALUBlockingCycles. (PR #226314)

[Matt Arsenault via llvm-commits]

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@@ -1024,8 +1024,11 @@ class GCNSubtarget final : public AMDGPUGenSubtargetInfo,
   }
 
   /// True if VALU pipe occupancy is modeled with GFX1250BlockingCycles
-  /// (gfx1250 pipeline property, not gfx1250 ISA feature).
-  bool hasGFX1250VALUBlockingCycles() const { return AMDGPU::isGFX1250(*this); }
+  /// (gfx1250 pipeline property, not gfx1250 ISA feature). Full-rate 64-bit
+  /// chips (gfx1251) do not use this occupancy table.
+  bool hasGFX1250VALUBlockingCycles() const {
+    return AMDGPU::isGFX1250(*this) && !hasFullRate64Ops();
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arsenm wrote:

Shouldn't use the AMDGPU:: predicates, this is already the subtarget. This also really should be its own feature. The 1250 in the name is confusing given it applies more broadly 

https://github.com/llvm/llvm-project/pull/226314