[AArch64][GlobalISel] Legalize load <2 x i16>

[paquette]

LGTM with nit

llvm/test/CodeGen/AArch64/GlobalISel/legalize-load-store.mir

582

Same test nit as for D105912

llvm/lib/Target/AArch64/GISel/AArch64LegalizerInfo.cpp

getActionDefinitionsBuilder(G_LOAD)
       // Lower any any-extending loads left into G_ANYEXT and G_LOAD
       .lowerIf([=](const LegalityQuery &Query) {
         return Query.Types[0] != Query.MMODescrs[0].MemoryTy;
       })
       .clampMaxNumElements(0, s8, 16)
       .clampMaxNumElements(0, s16, 8)
       .clampMaxNumElements(0, s32, 4)
       .clampMaxNumElements(0, s64, 2)
-      .customIf(IsPtrVecPred);
+      .customIf(IsPtrVecPred)
+      .scalarizeIf(typeIs(0, v2s16), 0);
 
   getActionDefinitionsBuilder(G_STORE)
       .legalForTypesWithMemDesc({{s8, p0, s8, 8},
                                  {s16, p0, s8, 8}, // truncstorei8 from s16
                                  {s32, p0, s8, 8}, // truncstorei8 from s32
                                  {s64, p0, s8, 8}, // truncstorei8 from s64
                                  {s16, p0, s16, 8},
                                  {s32, p0, s16, 8}, // truncstorei16 from s32
getActionDefinitionsBuilder(G_EXTRACT_VECTOR_ELT)
       .clampMaxNumElements(1, s16, 8);
 
   getActionDefinitionsBuilder(G_INSERT_VECTOR_ELT)
       .legalIf(typeInSet(0, {v8s16, v2s32, v4s32, v2s64}));
 
   getActionDefinitionsBuilder(G_BUILD_VECTOR)
       .legalFor({{v8s8, s8},
                  {v16s8, s8},
+                 {v2s16, s16},
                  {v4s16, s16},
                  {v8s16, s16},
                  {v2s32, s32},
                  {v4s32, s32},
                  {v2p0, p0},
                  {v2s64, s64}})
       .clampNumElements(0, v4s32, v4s32)
       .clampNumElements(0, v2s64, v2s64)

llvm/test/CodeGen/AArch64/GlobalISel/legalize-load-store.mir

bb.1:
     ; CHECK: G_STORE [[UV1]](s16), [[PTR_ADD]](p0) :: (store (s16) into unknown-address + 2)
     ; CHECK: RET_ReallyLR
     %0:_(p0) = COPY $x0
     %1:_(<2 x s16>) = COPY $s0
     G_STORE %1(<2 x s16>), %0(p0) :: (store (<2 x s16>))
     RET_ReallyLR
 
 ...
+---
+name:            load_2xi16
+alignment:       4
+tracksRegLiveness: true
+registers:
+  - { id: 0, class: _ }
+  - { id: 1, class: _ }
+liveins:
+  - { reg: '$x0' }
+  - { reg: '$s0' }
+frameInfo:
+  maxAlignment:    1
+machineFunctionInfo: {}
+body:             |
+  bb.1:
+    liveins: $s0, $x0
+
+    ; CHECK-LABEL: name: load_2xi16
+    ; CHECK: liveins: $s0, $x0
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
+    ; CHECK: [[LOAD:%[0-9]+]]:_(s16) = G_LOAD [[COPY]](p0) :: (load (s16), align 4)
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 2
+    ; CHECK: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C]](s64)
+    ; CHECK: [[LOAD1:%[0-9]+]]:_(s16) = G_LOAD [[PTR_ADD]](p0) :: (load (s16) from unknown-address + 2)
+    ; CHECK: [[BUILD_VECTOR:%[0-9]+]]:_(<2 x s16>) = G_BUILD_VECTOR [[LOAD]](s16), [[LOAD1]](s16)
+    ; CHECK: $s0 = COPY [[BUILD_VECTOR]](<2 x s16>)
+    ; CHECK: RET_ReallyLR
+    %0:_(p0) = COPY $x0
+    %1(<2 x s16>) = G_LOAD %0(p0) :: (load (<2 x s16>))
+    $s0 = COPY %1:_(<2 x s16>)
+    RET_ReallyLR
+
+...