Index: llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
===================================================================
--- llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
+++ llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
@@ -221,6 +221,7 @@
   LegalizeResult narrowScalarBasic(MachineInstr &MI, unsigned TypeIdx, LLT Ty);
   LegalizeResult narrowScalarSelect(MachineInstr &MI, unsigned TypeIdx, LLT Ty);
 
+  LegalizeResult lowerBitcast(MachineInstr &MI);
   LegalizeResult lowerBitCount(MachineInstr &MI, unsigned TypeIdx, LLT Ty);
 
   LegalizeResult lowerU64ToF32BitOps(MachineInstr &MI);
Index: llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -1935,6 +1935,39 @@
   }
 }
 
+static void getUnmergePieces(SmallVectorImpl<Register> &Pieces,
+                             MachineIRBuilder &B, Register Src, LLT Ty) {
+  auto Unmerge = B.buildUnmerge(Ty, Src);
+  for (int I = 0, E = Unmerge->getNumOperands() - 1; I != E; ++I)
+    Pieces.push_back(Unmerge.getReg(I));
+}
+
+LegalizerHelper::LegalizeResult
+LegalizerHelper::lowerBitcast(MachineInstr &MI) {
+  Register Dst = MI.getOperand(0).getReg();
+  Register Src = MI.getOperand(1).getReg();
+  LLT DstTy = MRI.getType(Dst);
+  LLT SrcTy = MRI.getType(Src);
+
+  if (SrcTy.isVector() && !DstTy.isVector()) {
+    SmallVector<Register, 8> SrcRegs;
+    getUnmergePieces(SrcRegs, MIRBuilder, Src, SrcTy.getElementType());
+    MIRBuilder.buildMerge(Dst, SrcRegs);
+    MI.eraseFromParent();
+    return Legalized;
+  }
+
+  if (DstTy.isVector() && !SrcTy.isVector()) {
+    SmallVector<Register, 8> SrcRegs;
+    getUnmergePieces(SrcRegs, MIRBuilder, Src, DstTy.getElementType());
+    MIRBuilder.buildMerge(Dst, SrcRegs);
+    MI.eraseFromParent();
+    return Legalized;
+  }
+
+  return UnableToLegalize;
+}
+
 LegalizerHelper::LegalizeResult
 LegalizerHelper::lower(MachineInstr &MI, unsigned TypeIdx, LLT Ty) {
   using namespace TargetOpcode;
@@ -1943,6 +1976,8 @@
   switch(MI.getOpcode()) {
   default:
     return UnableToLegalize;
+  case TargetOpcode::G_BITCAST:
+    return lowerBitcast(MI);
   case TargetOpcode::G_SREM:
   case TargetOpcode::G_UREM: {
     Register QuotReg = MRI.createGenericVirtualRegister(Ty);
Index: llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPULegalizerInfo.cpp
@@ -308,7 +308,9 @@
     // Don't worry about the size constraint.
     .legalIf(all(isRegisterType(0), isRegisterType(1)))
     // FIXME: Testing hack
-    .legalForCartesianProduct({S16, LLT::vector(2, 8), });
+    .legalForCartesianProduct({S16, LLT::vector(2, 8), })
+    .lower();
+
 
   getActionDefinitionsBuilder(G_FCONSTANT)
     .legalFor({S32, S64, S16})
Index: llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-bitcast.mir
===================================================================
--- llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-bitcast.mir
+++ llvm/test/CodeGen/AMDGPU/GlobalISel/legalize-bitcast.mir
@@ -1,5 +1,5 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
-# RUN: llc -mtriple=amdgcn-mesa-mesa3d -mcpu=fiji -run-pass=legalizer %s -o - | FileCheck %s
+# RUN: llc -mtriple=amdgcn-mesa-mesa3d -mcpu=fiji -run-pass=legalizer -global-isel-abort=0 %s -o - | FileCheck %s
 
 ---
 name: test_bitcast_s32_to_v2s16
@@ -282,3 +282,154 @@
     %1:_(<8 x s64>) = G_BITCAST %0
     $vgpr0_vgpr1_vgpr2_vgpr3_vgpr4_vgpr5_vgpr6_vgpr7_vgpr8_vgpr9_vgpr10_vgpr11_vgpr12_vgpr13_vgpr14_vgpr15 = COPY %1
 ...
+
+---
+name: test_bitcast_s24_to_v3s8
+body: |
+  bb.0:
+    liveins: $vgpr0
+
+    ; CHECK-LABEL: name: test_bitcast_s24_to_v3s8
+    ; CHECK: [[COPY:%[0-9]+]]:_(s32) = COPY $vgpr0
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 8
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s48) = G_TRUNC [[C]](s64)
+    ; CHECK: [[TRUNC1:%[0-9]+]]:_(s32) = G_TRUNC [[TRUNC]](s48)
+    ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 16777215
+    ; CHECK: [[ANYEXT:%[0-9]+]]:_(s64) = G_ANYEXT [[COPY]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s64) = G_AND [[ANYEXT]], [[C1]]
+    ; CHECK: [[SHL:%[0-9]+]]:_(s64) = G_SHL [[AND]], [[TRUNC1]](s32)
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s64) = COPY [[SHL]](s64)
+    ; CHECK: [[OR:%[0-9]+]]:_(s64) = G_OR [[AND]], [[COPY1]]
+    ; CHECK: [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 16
+    ; CHECK: [[TRUNC2:%[0-9]+]]:_(s48) = G_TRUNC [[C2]](s64)
+    ; CHECK: [[TRUNC3:%[0-9]+]]:_(s32) = G_TRUNC [[TRUNC2]](s48)
+    ; CHECK: [[COPY2:%[0-9]+]]:_(s64) = COPY [[OR]](s64)
+    ; CHECK: [[SHL1:%[0-9]+]]:_(s64) = G_SHL [[COPY2]], [[TRUNC3]](s32)
+    ; CHECK: [[COPY3:%[0-9]+]]:_(s64) = COPY [[SHL1]](s64)
+    ; CHECK: [[OR1:%[0-9]+]]:_(s64) = G_OR [[COPY2]], [[COPY3]]
+    ; CHECK: [[TRUNC4:%[0-9]+]]:_(s48) = G_TRUNC [[OR1]](s64)
+    ; CHECK: [[UV:%[0-9]+]]:_(s16), [[UV1:%[0-9]+]]:_(s16), [[UV2:%[0-9]+]]:_(s16) = G_UNMERGE_VALUES [[TRUNC4]](s48)
+    ; CHECK: [[ANYEXT1:%[0-9]+]]:_(s32) = G_ANYEXT [[UV]](s16)
+    ; CHECK: [[ANYEXT2:%[0-9]+]]:_(s32) = G_ANYEXT [[UV1]](s16)
+    ; CHECK: [[ANYEXT3:%[0-9]+]]:_(s32) = G_ANYEXT [[UV2]](s16)
+    ; CHECK: [[COPY4:%[0-9]+]]:_(s32) = COPY [[ANYEXT1]](s32)
+    ; CHECK: [[COPY5:%[0-9]+]]:_(s32) = COPY [[ANYEXT2]](s32)
+    ; CHECK: [[COPY6:%[0-9]+]]:_(s32) = COPY [[ANYEXT3]](s32)
+    ; CHECK: [[BUILD_VECTOR:%[0-9]+]]:_(<3 x s32>) = G_BUILD_VECTOR [[COPY4]](s32), [[COPY5]](s32), [[COPY6]](s32)
+    ; CHECK: $vgpr0_vgpr1_vgpr2 = COPY [[BUILD_VECTOR]](<3 x s32>)
+    %0:_(s32) = COPY $vgpr0
+    %1:_(s24) = G_TRUNC %0
+    %2:_(<3 x s8>) = G_BITCAST %1
+    %3:_(<3 x s32>) = G_ANYEXT %2
+    $vgpr0_vgpr1_vgpr2 = COPY %3
+...
+
+---
+name: test_bitcast_s48_to_v3s16
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1
+
+    ; CHECK-LABEL: name: test_bitcast_s48_to_v3s16
+    ; CHECK: [[COPY:%[0-9]+]]:_(s64) = COPY $vgpr0_vgpr1
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(s48) = G_TRUNC [[COPY]](s64)
+    ; CHECK: [[UV:%[0-9]+]]:_(s16), [[UV1:%[0-9]+]]:_(s16), [[UV2:%[0-9]+]]:_(s16) = G_UNMERGE_VALUES [[TRUNC]](s48)
+    ; CHECK: [[DEF:%[0-9]+]]:_(s16) = G_IMPLICIT_DEF
+    ; CHECK: [[BUILD_VECTOR:%[0-9]+]]:_(<2 x s16>) = G_BUILD_VECTOR [[UV]](s16), [[UV1]](s16)
+    ; CHECK: [[BUILD_VECTOR1:%[0-9]+]]:_(<2 x s16>) = G_BUILD_VECTOR [[UV2]](s16), [[DEF]](s16)
+    ; CHECK: [[CONCAT_VECTORS:%[0-9]+]]:_(<4 x s16>) = G_CONCAT_VECTORS [[BUILD_VECTOR]](<2 x s16>), [[BUILD_VECTOR1]](<2 x s16>)
+    ; CHECK: [[EXTRACT:%[0-9]+]]:_(<3 x s16>) = G_EXTRACT [[CONCAT_VECTORS]](<4 x s16>), 0
+    ; CHECK: [[DEF1:%[0-9]+]]:_(<4 x s16>) = G_IMPLICIT_DEF
+    ; CHECK: [[INSERT:%[0-9]+]]:_(<4 x s16>) = G_INSERT [[DEF1]], [[EXTRACT]](<3 x s16>), 0
+    ; CHECK: [[UV3:%[0-9]+]]:_(<2 x s16>), [[UV4:%[0-9]+]]:_(<2 x s16>) = G_UNMERGE_VALUES [[INSERT]](<4 x s16>)
+    ; CHECK: [[BITCAST:%[0-9]+]]:_(s32) = G_BITCAST [[UV3]](<2 x s16>)
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 16
+    ; CHECK: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[BITCAST]], [[C]](s32)
+    ; CHECK: [[BITCAST1:%[0-9]+]]:_(s32) = G_BITCAST [[UV4]](<2 x s16>)
+    ; CHECK: [[LSHR1:%[0-9]+]]:_(s32) = G_LSHR [[BITCAST1]], [[C]](s32)
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[BITCAST]](s32)
+    ; CHECK: [[COPY2:%[0-9]+]]:_(s32) = COPY [[LSHR]](s32)
+    ; CHECK: [[COPY3:%[0-9]+]]:_(s32) = COPY [[BITCAST1]](s32)
+    ; CHECK: [[BUILD_VECTOR2:%[0-9]+]]:_(<3 x s32>) = G_BUILD_VECTOR [[COPY1]](s32), [[COPY2]](s32), [[COPY3]](s32)
+    ; CHECK: $vgpr0_vgpr1_vgpr2 = COPY [[BUILD_VECTOR2]](<3 x s32>)
+    %0:_(s64) = COPY $vgpr0_vgpr1
+    %1:_(s48) = G_TRUNC %0
+    %2:_(<3 x s16>) = G_BITCAST %1
+    %3:_(<3 x s32>) = G_ANYEXT %2
+    $vgpr0_vgpr1_vgpr2 = COPY %3
+...
+
+---
+name: test_bitcast_v3s8_to_s24
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1_vgpr2
+
+    ; CHECK-LABEL: name: test_bitcast_v3s8_to_s24
+    ; CHECK: [[COPY:%[0-9]+]]:_(<3 x s32>) = COPY $vgpr0_vgpr1_vgpr2
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(<3 x s8>) = G_TRUNC [[COPY]](<3 x s32>)
+    ; CHECK: [[UV:%[0-9]+]]:_(s8), [[UV1:%[0-9]+]]:_(s8), [[UV2:%[0-9]+]]:_(s8) = G_UNMERGE_VALUES [[TRUNC]](<3 x s8>)
+    ; CHECK: [[DEF:%[0-9]+]]:_(s32) = G_IMPLICIT_DEF
+    ; CHECK: [[ZEXT:%[0-9]+]]:_(s16) = G_ZEXT [[UV]](s8)
+    ; CHECK: [[ZEXT1:%[0-9]+]]:_(s16) = G_ZEXT [[UV1]](s8)
+    ; CHECK: [[C:%[0-9]+]]:_(s16) = G_CONSTANT i16 8
+    ; CHECK: [[SHL:%[0-9]+]]:_(s16) = G_SHL [[ZEXT1]], [[C]](s16)
+    ; CHECK: [[OR:%[0-9]+]]:_(s16) = G_OR [[ZEXT]], [[SHL]]
+    ; CHECK: [[ZEXT2:%[0-9]+]]:_(s16) = G_ZEXT [[UV2]](s8)
+    ; CHECK: [[C1:%[0-9]+]]:_(s16) = G_CONSTANT i16 255
+    ; CHECK: [[TRUNC1:%[0-9]+]]:_(s16) = G_TRUNC [[DEF]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s16) = G_AND [[TRUNC1]], [[C1]]
+    ; CHECK: [[SHL1:%[0-9]+]]:_(s16) = G_SHL [[AND]], [[C]](s16)
+    ; CHECK: [[OR1:%[0-9]+]]:_(s16) = G_OR [[ZEXT2]], [[SHL1]]
+    ; CHECK: [[ZEXT3:%[0-9]+]]:_(s32) = G_ZEXT [[OR]](s16)
+    ; CHECK: [[ZEXT4:%[0-9]+]]:_(s32) = G_ZEXT [[OR1]](s16)
+    ; CHECK: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 16
+    ; CHECK: [[SHL2:%[0-9]+]]:_(s32) = G_SHL [[ZEXT4]], [[C2]](s32)
+    ; CHECK: [[OR2:%[0-9]+]]:_(s32) = G_OR [[ZEXT3]], [[SHL2]]
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[OR2]](s32)
+    ; CHECK: $vgpr0 = COPY [[COPY1]](s32)
+    %0:_(<3 x s32>) = COPY $vgpr0_vgpr1_vgpr2
+    %1:_(<3 x s8>) = G_TRUNC %0
+    %2:_(s24) = G_BITCAST %1
+    %3:_(s32) = G_ANYEXT %2
+    $vgpr0 = COPY %3
+...
+
+---
+name: test_bitcast_v3s16_to_s48
+body: |
+  bb.0:
+    liveins: $vgpr0_vgpr1_vgpr2
+
+    ; CHECK-LABEL: name: test_bitcast_v3s16_to_s48
+    ; CHECK: [[COPY:%[0-9]+]]:_(<3 x s32>) = COPY $vgpr0_vgpr1_vgpr2
+    ; CHECK: [[TRUNC:%[0-9]+]]:_(<3 x s16>) = G_TRUNC [[COPY]](<3 x s32>)
+    ; CHECK: [[DEF:%[0-9]+]]:_(<4 x s16>) = G_IMPLICIT_DEF
+    ; CHECK: [[INSERT:%[0-9]+]]:_(<4 x s16>) = G_INSERT [[DEF]], [[TRUNC]](<3 x s16>), 0
+    ; CHECK: [[UV:%[0-9]+]]:_(<2 x s16>), [[UV1:%[0-9]+]]:_(<2 x s16>) = G_UNMERGE_VALUES [[INSERT]](<4 x s16>)
+    ; CHECK: [[BITCAST:%[0-9]+]]:_(s32) = G_BITCAST [[UV]](<2 x s16>)
+    ; CHECK: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 16
+    ; CHECK: [[LSHR:%[0-9]+]]:_(s32) = G_LSHR [[BITCAST]], [[C]](s32)
+    ; CHECK: [[BITCAST1:%[0-9]+]]:_(s32) = G_BITCAST [[UV1]](<2 x s16>)
+    ; CHECK: [[LSHR1:%[0-9]+]]:_(s32) = G_LSHR [[BITCAST1]], [[C]](s32)
+    ; CHECK: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 65535
+    ; CHECK: [[COPY1:%[0-9]+]]:_(s32) = COPY [[BITCAST]](s32)
+    ; CHECK: [[AND:%[0-9]+]]:_(s32) = G_AND [[COPY1]], [[C1]]
+    ; CHECK: [[COPY2:%[0-9]+]]:_(s32) = COPY [[LSHR]](s32)
+    ; CHECK: [[AND1:%[0-9]+]]:_(s32) = G_AND [[COPY2]], [[C1]]
+    ; CHECK: [[SHL:%[0-9]+]]:_(s32) = G_SHL [[AND1]], [[C]](s32)
+    ; CHECK: [[OR:%[0-9]+]]:_(s32) = G_OR [[AND]], [[SHL]]
+    ; CHECK: [[COPY3:%[0-9]+]]:_(s32) = COPY [[BITCAST1]](s32)
+    ; CHECK: [[AND2:%[0-9]+]]:_(s32) = G_AND [[COPY3]], [[C1]]
+    ; CHECK: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
+    ; CHECK: [[SHL1:%[0-9]+]]:_(s32) = G_SHL [[C2]], [[C]](s32)
+    ; CHECK: [[OR1:%[0-9]+]]:_(s32) = G_OR [[AND2]], [[SHL1]]
+    ; CHECK: [[MV:%[0-9]+]]:_(s64) = G_MERGE_VALUES [[OR]](s32), [[OR1]](s32)
+    ; CHECK: [[COPY4:%[0-9]+]]:_(s64) = COPY [[MV]](s64)
+    ; CHECK: $vgpr0_vgpr1 = COPY [[COPY4]](s64)
+    %0:_(<3 x s32>) = COPY $vgpr0_vgpr1_vgpr2
+    %1:_(<3 x s16>) = G_TRUNC %0
+    %2:_(s48) = G_BITCAST %1
+    %3:_(s64) = G_ANYEXT %2
+    $vgpr0_vgpr1 = COPY %3
+...