[AArch64][GlobalISel] Make <8 x s8> of G_BUILD_VECTOR legal.

Author: aemerson

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

@@ -599,7 +599,8 @@ AArch64LegalizerInfo::AArch64LegalizerInfo(const AArch64Subtarget &ST)
       });
 
   getActionDefinitionsBuilder(G_BUILD_VECTOR)
-      .legalFor({{v16s8, s8},
+      .legalFor({{v8s8, s8},
+                 {v16s8, s8},
                  {v4s16, s16},
                  {v8s16, s16},
                  {v2s32, s32},

llvm/test/CodeGen/AArch64/GlobalISel/legalize-build-vector.mir

@@ -72,3 +72,19 @@ body: |
     $q0 = COPY %2(<16 x s8>)
     RET_ReallyLR
 ...
+---
+name:            legal_v8s8
+body: |
+  bb.0:
+    ; CHECK-LABEL: name: legal_v8s8
+    ; CHECK: [[DEF:%[0-9]+]]:_(s8) = G_IMPLICIT_DEF
+    ; CHECK: [[DEF1:%[0-9]+]]:_(s8) = G_IMPLICIT_DEF
+    ; CHECK: [[BUILD_VECTOR:%[0-9]+]]:_(<8 x s8>) = G_BUILD_VECTOR [[DEF]](s8), [[DEF1]](s8), [[DEF]](s8), [[DEF1]](s8), [[DEF]](s8), [[DEF1]](s8), [[DEF]](s8), [[DEF1]](s8)
+    ; CHECK: $d0 = COPY [[BUILD_VECTOR]](<8 x s8>)
+    ; CHECK: RET_ReallyLR
+    %0:_(s8) = G_IMPLICIT_DEF
+    %1:_(s8) = G_IMPLICIT_DEF
+    %2:_(<8 x s8>) = G_BUILD_VECTOR %0(s8), %1(s8), %0(s8), %1(s8), %0(s8), %1(s8), %0(s8), %1(s8)
+    $d0 = COPY %2(<8 x s8>)
+    RET_ReallyLR
+...