[llvm] [AArch64] Optimize extending loads of small vectors (PR #163064)

[Guy David via llvm-commits]

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@@ -1427,12 +1427,27 @@ AArch64TargetLowering::AArch64TargetLowering(const TargetMachine &TM,
     setOperationAction(ISD::BITCAST, MVT::v2i16, Custom);
     setOperationAction(ISD::BITCAST, MVT::v4i8, Custom);
 
-    setLoadExtAction(ISD::EXTLOAD,  MVT::v4i16, MVT::v4i8, Custom);
+    setLoadExtAction(ISD::EXTLOAD, MVT::v2i32, MVT::v2i8, Custom);
+    setLoadExtAction(ISD::SEXTLOAD, MVT::v2i32, MVT::v2i8, Custom);
+    setLoadExtAction(ISD::ZEXTLOAD, MVT::v2i32, MVT::v2i8, Custom);
+    setLoadExtAction(ISD::EXTLOAD, MVT::v2i64, MVT::v2i8, Custom);
+    setLoadExtAction(ISD::SEXTLOAD, MVT::v2i64, MVT::v2i8, Custom);
+    setLoadExtAction(ISD::ZEXTLOAD, MVT::v2i64, MVT::v2i8, Custom);
+    setLoadExtAction(ISD::EXTLOAD, MVT::v4i16, MVT::v4i8, Custom);
     setLoadExtAction(ISD::SEXTLOAD, MVT::v4i16, MVT::v4i8, Custom);
     setLoadExtAction(ISD::ZEXTLOAD, MVT::v4i16, MVT::v4i8, Custom);
-    setLoadExtAction(ISD::EXTLOAD,  MVT::v4i32, MVT::v4i8, Custom);
+    setLoadExtAction(ISD::EXTLOAD, MVT::v4i32, MVT::v4i8, Custom);
     setLoadExtAction(ISD::SEXTLOAD, MVT::v4i32, MVT::v4i8, Custom);
     setLoadExtAction(ISD::ZEXTLOAD, MVT::v4i32, MVT::v4i8, Custom);
+    setLoadExtAction(ISD::EXTLOAD, MVT::v2i32, MVT::v2i16, Custom);
+    setLoadExtAction(ISD::SEXTLOAD, MVT::v2i32, MVT::v2i16, Custom);
+    setLoadExtAction(ISD::ZEXTLOAD, MVT::v2i32, MVT::v2i16, Custom);
+    setLoadExtAction(ISD::EXTLOAD, MVT::v2i64, MVT::v2i16, Custom);
+    setLoadExtAction(ISD::SEXTLOAD, MVT::v2i64, MVT::v2i16, Custom);
+    setLoadExtAction(ISD::ZEXTLOAD, MVT::v2i64, MVT::v2i16, Custom);
+    setLoadExtAction(ISD::EXTLOAD, MVT::v4i32, MVT::v4i16, Custom);
+    setLoadExtAction(ISD::SEXTLOAD, MVT::v4i32, MVT::v4i16, Custom);
+    setLoadExtAction(ISD::ZEXTLOAD, MVT::v4i32, MVT::v4i16, Custom);
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guy-david wrote:

Tried to exclude `v4i16` and a specific case of `zext (load <4 x i16>)` degraded into a pair of loads when SVE is enabled. Seems like there's more to improve upon in `isVectorLoadExtDesirable`.

https://github.com/llvm/llvm-project/pull/163064