Index: lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
===================================================================
--- lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
+++ lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
@@ -38,6 +38,8 @@
   const LLT S512 = LLT::scalar(512);
 
   const LLT V2S16 = LLT::vector(2, 16);
+  const LLT V4S16 = LLT::vector(4, 16);
+  const LLT V8S16 = LLT::vector(8, 16);
 
   const LLT V2S32 = LLT::vector(2, 32);
   const LLT V3S32 = LLT::vector(3, 32);
@@ -303,6 +305,16 @@
     .clampNumElements(0, V2S64, V8S64)
     .minScalarSameAs(1, 0);
 
+  // TODO: Support any combination of v2s32
+  getActionDefinitionsBuilder(G_CONCAT_VECTORS)
+    .legalFor({{V4S32, V2S32},
+               {V8S32, V2S32},
+               {V8S32, V4S32},
+               {V4S64, V2S64},
+               {V4S16, V2S16},
+               {V8S16, V2S16},
+               {V8S16, V4S16}});
+
   // Merge/Unmerge
   for (unsigned Op : {G_MERGE_VALUES, G_UNMERGE_VALUES}) {
     unsigned BigTyIdx = Op == G_MERGE_VALUES ? 0 : 1;
Index: test/CodeGen/AMDGPU/GlobalISel/legalize-concat-vectors.mir
===================================================================
--- /dev/null
+++ test/CodeGen/AMDGPU/GlobalISel/legalize-concat-vectors.mir
@@ -0,0 +1,130 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=amdgcn-mesa-mesa3d -mcpu=fiji -O0 -run-pass=legalizer %s -o - | FileCheck %s
+
+---
+name: concat_vectors_v2s32_v2s32
+
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2_vgpr3
+    ; CHECK-LABEL: name: concat_vectors_v2s32_v2s32
+    ; CHECK: [[COPY:%[0-9]+]]:_(<2 x s32>) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(<2 x s32>) = COPY $vgpr2_vgpr3
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<4 x s32>) = G_CONCAT_VECTORS [[COPY]](<2 x s32>), [[COPY1]](<2 x s32>)
+    ; CHECK: $vgpr0_vgpr1_vgpr2_vgpr3 = COPY [[CONCAT_VECTORS]](<4 x s32>)
+    %0:_(<2 x s32>) = COPY $vgpr0_vgpr1
+    %1:_(<2 x s32>) = COPY $vgpr2_vgpr3
+    %2:_(<4 x s32>) = G_CONCAT_VECTORS %0, %1
+    $vgpr0_vgpr1_vgpr2_vgpr3 = COPY %2
+...
+
+---
+name: concat_vectors_v2s16_v2s16
+
+body: |
+  bb.0:
+    liveins: $vgpr0, $vgpr1
+    ; CHECK-LABEL: name: concat_vectors_v2s16_v2s16
+    ; CHECK: [[COPY:%[0-9]+]]:_(<2 x s16>) = COPY $vgpr0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(<2 x s16>) = COPY $vgpr1
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<4 x s16>) = G_CONCAT_VECTORS [[COPY]](<2 x s16>), [[COPY1]](<2 x s16>)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[CONCAT_VECTORS]](<4 x s16>)
+    %0:_(<2 x s16>) = COPY $vgpr0
+    %1:_(<2 x s16>) = COPY $vgpr1
+    %2:_(<4 x s16>) = G_CONCAT_VECTORS %0, %1
+    $vgpr0_vgpr1 = COPY %2
+...
+
+---
+name: concat_vectors_v2s16_v2s16_v2s16_v2s16
+
+body: |
+  bb.0:
+    liveins: $vgpr0, $vgpr1, $vgpr2, $vgpr3
+    ; CHECK-LABEL: name: concat_vectors_v2s16_v2s16_v2s16_v2s16
+    ; CHECK: [[COPY:%[0-9]+]]:_(<2 x s16>) = COPY $vgpr0
+    ; CHECK: [[COPY1:%[0-9]+]]:_(<2 x s16>) = COPY $vgpr1
+    ; CHECK: [[COPY2:%[0-9]+]]:_(<2 x s16>) = COPY $vgpr2
+    ; CHECK: [[COPY3:%[0-9]+]]:_(<2 x s16>) = COPY $vgpr3
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<8 x s16>) = G_CONCAT_VECTORS [[COPY]](<2 x s16>), [[COPY1]](<2 x s16>), [[COPY2]](<2 x s16>), [[COPY3]](<2 x s16>)
+    ; CHECK: $vgpr0_vgpr1_vgpr2_vgpr3 = COPY [[CONCAT_VECTORS]](<8 x s16>)
+    %0:_(<2 x s16>) = COPY $vgpr0
+    %1:_(<2 x s16>) = COPY $vgpr1
+    %2:_(<2 x s16>) = COPY $vgpr2
+    %3:_(<2 x s16>) = COPY $vgpr3
+    %4:_(<8 x s16>) = G_CONCAT_VECTORS %0, %1, %2, %3
+    $vgpr0_vgpr1_vgpr2_vgpr3 = COPY %4
+...
+
+---
+name: concat_vectors_v4s16_v4s16
+
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2_vgpr3
+    ; CHECK-LABEL: name: concat_vectors_v4s16_v4s16
+    ; CHECK: [[COPY:%[0-9]+]]:_(<4 x s16>) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(<4 x s16>) = COPY $vgpr2_vgpr3
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<8 x s16>) = G_CONCAT_VECTORS [[COPY]](<4 x s16>), [[COPY1]](<4 x s16>)
+    ; CHECK: $vgpr0_vgpr1_vgpr2_vgpr3 = COPY [[CONCAT_VECTORS]](<8 x s16>)
+    %0:_(<4 x s16>) = COPY $vgpr0_vgpr1
+    %1:_(<4 x s16>) = COPY $vgpr2_vgpr3
+    %2:_(<8 x s16>) = G_CONCAT_VECTORS %0, %1
+    $vgpr0_vgpr1_vgpr2_vgpr3 = COPY %2
+...
+
+---
+name: concat_vectors_v4s32_v4s32
+
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1_vgpr2_vgpr3, $vgpr4_vgpr5_vgpr6_vgpr7
+    ; CHECK-LABEL: name: concat_vectors_v4s32_v4s32
+    ; CHECK: [[COPY:%[0-9]+]]:_(<4 x s32>) = COPY $vgpr0_vgpr1_vgpr2_vgpr3
+    ; CHECK: [[COPY1:%[0-9]+]]:_(<4 x s32>) = COPY $vgpr4_vgpr5_vgpr6_vgpr7
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<8 x s32>) = G_CONCAT_VECTORS [[COPY]](<4 x s32>), [[COPY1]](<4 x s32>)
+    ; CHECK: $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7 = COPY [[CONCAT_VECTORS]](<8 x s32>)
+    %0:_(<4 x s32>) = COPY $vgpr0_vgpr1_vgpr2_vgpr3,
+    %1:_(<4 x s32>) = COPY $vgpr4_vgpr5_vgpr6_vgpr7
+    %2:_(<8 x s32>) = G_CONCAT_VECTORS %0, %1
+    $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7 = COPY %2
+...
+
+---
+name: concat_vectors_v2s32_v2s32_v2s32_v2s32
+
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1, $vgpr2_vgpr3, $vgpr4_vgpr5, $vgpr6_vgpr7
+    ; CHECK-LABEL: name: concat_vectors_v2s32_v2s32_v2s32_v2s32
+    ; CHECK: [[COPY:%[0-9]+]]:_(<2 x s32>) = COPY $vgpr0_vgpr1
+    ; CHECK: [[COPY1:%[0-9]+]]:_(<2 x s32>) = COPY $vgpr2_vgpr3
+    ; CHECK: [[COPY2:%[0-9]+]]:_(<2 x s32>) = COPY $vgpr4_vgpr5
+    ; CHECK: [[COPY3:%[0-9]+]]:_(<2 x s32>) = COPY $vgpr6_vgpr7
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<8 x s32>) = G_CONCAT_VECTORS [[COPY]](<2 x s32>), [[COPY1]](<2 x s32>), [[COPY2]](<2 x s32>), [[COPY3]](<2 x s32>)
+    ; CHECK: $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7 = COPY [[CONCAT_VECTORS]](<8 x s32>)
+    %0:_(<2 x s32>) = COPY $vgpr0_vgpr1
+    %1:_(<2 x s32>) = COPY $vgpr2_vgpr3
+    %2:_(<2 x s32>) = COPY $vgpr4_vgpr5
+    %3:_(<2 x s32>) = COPY $vgpr6_vgpr7
+
+    %4:_(<8 x s32>) = G_CONCAT_VECTORS %0, %1, %2, %3
+    $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7 = COPY %4
+...
+---
+name: concat_vectors_v2s64_v2s64
+
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1_vgpr2_vgpr3, $vgpr4_vgpr5_vgpr6_vgpr7
+    ; CHECK-LABEL: name: concat_vectors_v2s64_v2s64
+    ; CHECK: [[COPY:%[0-9]+]]:_(<2 x s64>) = COPY $vgpr0_vgpr1_vgpr2_vgpr3
+    ; CHECK: [[COPY1:%[0-9]+]]:_(<2 x s64>) = COPY $vgpr4_vgpr5_vgpr6_vgpr7
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<4 x s64>) = G_CONCAT_VECTORS [[COPY]](<2 x s64>), [[COPY1]](<2 x s64>)
+    ; CHECK: $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7 = COPY [[CONCAT_VECTORS]](<4 x s64>)
+    %0:_(<2 x s64>) = COPY $vgpr0_vgpr1_vgpr2_vgpr3
+    %1:_(<2 x s64>) = COPY $vgpr4_vgpr5_vgpr6_vgpr7
+    %2:_(<4 x s64>) = G_CONCAT_VECTORS %0, %1
+    $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7 = COPY %2
+...
+