[llvm] [AMDGPU] Change default loop alignment for GFX9 and higher targets (PR #153065)

[Matt Arsenault via llvm-commits]

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@@ -1431,6 +1431,14 @@ def FeatureDisable : SubtargetFeature<"",
   "Dummy feature to disable assembler instructions"
 >;
 
+// GFX-9 & higher targets have a 16-dword Instruction Buffer and per-SQ
+// instruction store which can supply 4 dwords to each of the 2 waves per
+// cycle. Change default alignment to 4 dwords or 16 bytes.
+def FeaturePrefLoopAlign32B : SubtargetFeature<"loop-align",
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arsenm wrote:

Include the value in the feature name 

https://github.com/llvm/llvm-project/pull/153065