diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 225c4826f16..90642d72286 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -8210,18 +8210,20 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
   if (N0.getOpcode() == ISD::SHL && N0.hasOneUse() &&
       (!LegalOperations || TLI.isOperationLegalOrCustom(ISD::SHL, VT)) &&
       TLI.isTypeDesirableForOp(ISD::SHL, VT)) {
-    if (const ConstantSDNode *CAmt = isConstOrConstSplat(N0.getOperand(1))) {
-      uint64_t Amt = CAmt->getZExtValue();
-      unsigned Size = VT.getScalarSizeInBits();
+    SDValue Amt = N0.getOperand(1);
+    KnownBits Known;
+    DAG.computeKnownBits(Amt, Known);
+    unsigned Size = VT.getScalarSizeInBits();
+    if (Known.getBitWidth() - Known.countMinLeadingZeros() <= Log2_32(Size)) {
+      SDLoc SL(N);
+      EVT AmtVT = TLI.getShiftAmountTy(VT, DAG.getDataLayout());
 
-      if (Amt < Size) {
-        SDLoc SL(N);
-        EVT AmtVT = TLI.getShiftAmountTy(VT, DAG.getDataLayout());
-
-        SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(0));
-        return DAG.getNode(ISD::SHL, SL, VT, Trunc,
-                           DAG.getConstant(Amt, SL, AmtVT));
+      SDValue Trunc = DAG.getNode(ISD::TRUNCATE, SL, VT, N0.getOperand(0));
+      if (AmtVT != Amt.getValueType()) {
+        Amt = DAG.getZExtOrTrunc(Amt, SL, AmtVT);
+        AddToWorklist(Amt.getNode());
       }
+      return DAG.getNode(ISD::SHL, SL, VT, Trunc, Amt);
     }
   }
 
diff --git a/test/CodeGen/AMDGPU/alignbit-pat.ll b/test/CodeGen/AMDGPU/alignbit-pat.ll
index e60083ebb63..5176f47f977 100644
--- a/test/CodeGen/AMDGPU/alignbit-pat.ll
+++ b/test/CodeGen/AMDGPU/alignbit-pat.ll
@@ -16,23 +16,6 @@ bb:
   ret void
 }
 
-; GCN-LABEL: {{^}}alignbit_shl_pat:
-; GCN-DAG: s_load_dword s[[SHL:[0-9]+]]
-; GCN-DAG: load_dwordx2 v{{\[}}[[LO:[0-9]+]]:[[HI:[0-9]+]]{{\]}}
-; GCN-DAG: s_sub_i32 s[[SHR:[0-9]+]], 32, s[[SHL]]
-; GCN:     v_alignbit_b32 v{{[0-9]+}}, v[[HI]], v[[LO]], s[[SHR]]
-
-define amdgpu_kernel void @alignbit_shl_pat(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1, i32 %arg2) {
-bb:
-  %tmp = load i64, i64 addrspace(1)* %arg, align 8
-  %tmp3 = and i32 %arg2, 31
-  %tmp4 = zext i32 %tmp3 to i64
-  %tmp5 = shl i64 %tmp, %tmp4
-  %tmp6 = trunc i64 %tmp5 to i32
-  store i32 %tmp6, i32 addrspace(1)* %arg1, align 4
-  ret void
-}
-
 ; GCN-LABEL: {{^}}alignbit_shr_pat_v:
 ; GCN-DAG: load_dword v[[SHR:[0-9]+]],
 ; GCN-DAG: load_dwordx2 v{{\[}}[[LO:[0-9]+]]:[[HI:[0-9]+]]{{\]}}
@@ -53,27 +36,6 @@ bb:
   ret void
 }
 
-; GCN-LABEL: {{^}}alignbit_shl_pat_v:
-; GCN-DAG: load_dword v[[SHL:[0-9]+]],
-; GCN-DAG: load_dwordx2 v{{\[}}[[LO:[0-9]+]]:[[HI:[0-9]+]]{{\]}}
-; GCN-DAG: v_sub_i32_e32 v[[SHR:[0-9]+]], {{[^,]+}}, 32, v[[SHL]]
-; GCN: v_alignbit_b32 v{{[0-9]+}}, v[[HI]], v[[LO]], v[[SHR]]
-
-define amdgpu_kernel void @alignbit_shl_pat_v(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1) {
-bb:
-  %tid = tail call i32 @llvm.amdgcn.workitem.id.x()
-  %gep1 = getelementptr inbounds i64, i64 addrspace(1)* %arg, i32 %tid
-  %tmp = load i64, i64 addrspace(1)* %gep1, align 8
-  %gep2 = getelementptr inbounds i32, i32 addrspace(1)* %arg1, i32 %tid
-  %amt = load i32, i32 addrspace(1)* %gep2, align 4
-  %tmp3 = and i32 %amt, 31
-  %tmp4 = zext i32 %tmp3 to i64
-  %tmp5 = shl i64 %tmp, %tmp4
-  %tmp6 = trunc i64 %tmp5 to i32
-  store i32 %tmp6, i32 addrspace(1)* %gep2, align 4
-  ret void
-}
-
 ; GCN-LABEL: {{^}}alignbit_shr_pat_wrong_and30:
 ; Negative test, wrong constant
 ; GCN: v_lshr_b64
@@ -90,22 +52,6 @@ bb:
   ret void
 }
 
-; GCN-LABEL: {{^}}alignbit_shl_pat_wrong_and30:
-; Negative test, wrong constant
-; GCN: v_lshl_b64
-; GCN-NOT: v_alignbit_b32
-
-define amdgpu_kernel void @alignbit_shl_pat_wrong_and30(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1, i32 %arg2) {
-bb:
-  %tmp = load i64, i64 addrspace(1)* %arg, align 8
-  %tmp3 = and i32 %arg2, 30
-  %tmp4 = zext i32 %tmp3 to i64
-  %tmp5 = shl i64 %tmp, %tmp4
-  %tmp6 = trunc i64 %tmp5 to i32
-  store i32 %tmp6, i32 addrspace(1)* %arg1, align 4
-  ret void
-}
-
 ; GCN-LABEL: {{^}}alignbit_shr_pat_wrong_and63:
 ; Negative test, wrong constant
 ; GCN: v_lshr_b64
@@ -122,21 +68,6 @@ bb:
   ret void
 }
 
-; GCN-LABEL: {{^}}alignbit_shl_pat_wrong_and63:
-; Negative test, wrong constant
-; GCN: v_lshl_b64
-; GCN-NOT: v_alignbit_b32
-
-define amdgpu_kernel void @alignbit_shl_pat_wrong_and63(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1, i32 %arg2) {
-bb:
-  %tmp = load i64, i64 addrspace(1)* %arg, align 8
-  %tmp3 = and i32 %arg2, 63
-  %tmp4 = zext i32 %tmp3 to i64
-  %tmp5 = shl i64 %tmp, %tmp4
-  %tmp6 = trunc i64 %tmp5 to i32
-  store i32 %tmp6, i32 addrspace(1)* %arg1, align 4
-  ret void
-}
 declare i32 @llvm.amdgcn.workitem.id.x() #0
 
 attributes #0 = { nounwind readnone speculatable }
diff --git a/test/CodeGen/AMDGPU/shift-i64-opts.ll b/test/CodeGen/AMDGPU/shift-i64-opts.ll
index a803849be02..5306e190a4f 100644
--- a/test/CodeGen/AMDGPU/shift-i64-opts.ll
+++ b/test/CodeGen/AMDGPU/shift-i64-opts.ll
@@ -243,3 +243,77 @@ define amdgpu_kernel void @trunc_shl_31_i32_i64_multi_use(i32 addrspace(1)* %out
   store volatile i64 %shl, i64 addrspace(1)* %in
   ret void
 }
+
+; GCN-LABEL: {{^}}trunc_shl_and31:
+; GCN:     s_and_b32 s[[AMT:[0-9]+]], s{{[0-9]+}}, 31
+; GCN:     v_lshlrev_b32_e32 v{{[0-9]+}}, s[[AMT]], v{{[0-9]+}}
+; GCN-NOT: v_lshl_b64
+; GCN-NOT: v_lshlrev_b64
+define amdgpu_kernel void @trunc_shl_and31(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1, i32 %arg2) {
+bb:
+  %tmp = load i64, i64 addrspace(1)* %arg, align 8
+  %tmp3 = and i32 %arg2, 31
+  %tmp4 = zext i32 %tmp3 to i64
+  %tmp5 = shl i64 %tmp, %tmp4
+  %tmp6 = trunc i64 %tmp5 to i32
+  store i32 %tmp6, i32 addrspace(1)* %arg1, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}trunc_shl_and30:
+; GCN:     s_and_b32 s[[AMT:[0-9]+]], s{{[0-9]+}}, 30
+; GCN:     v_lshlrev_b32_e32 v{{[0-9]+}}, s[[AMT]], v{{[0-9]+}}
+; GCN-NOT: v_lshl_b64
+; GCN-NOT: v_lshlrev_b64
+define amdgpu_kernel void @trunc_shl_and30(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1, i32 %arg2) {
+bb:
+  %tmp = load i64, i64 addrspace(1)* %arg, align 8
+  %tmp3 = and i32 %arg2, 30
+  %tmp4 = zext i32 %tmp3 to i64
+  %tmp5 = shl i64 %tmp, %tmp4
+  %tmp6 = trunc i64 %tmp5 to i32
+  store i32 %tmp6, i32 addrspace(1)* %arg1, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}trunc_shl_wrong_and63:
+; Negative test, wrong constant
+; GCN: v_lshl_b64
+define amdgpu_kernel void @trunc_shl_wrong_and63(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1, i32 %arg2) {
+bb:
+  %tmp = load i64, i64 addrspace(1)* %arg, align 8
+  %tmp3 = and i32 %arg2, 63
+  %tmp4 = zext i32 %tmp3 to i64
+  %tmp5 = shl i64 %tmp, %tmp4
+  %tmp6 = trunc i64 %tmp5 to i32
+  store i32 %tmp6, i32 addrspace(1)* %arg1, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}trunc_shl_no_and:
+; Negative test, shift can be full 64 bit
+; GCN: v_lshl_b64
+define amdgpu_kernel void @trunc_shl_no_and(i64 addrspace(1)* nocapture readonly %arg, i32 addrspace(1)* nocapture %arg1, i32 %arg2) {
+bb:
+  %tmp = load i64, i64 addrspace(1)* %arg, align 8
+  %tmp4 = zext i32 %arg2 to i64
+  %tmp5 = shl i64 %tmp, %tmp4
+  %tmp6 = trunc i64 %tmp5 to i32
+  store i32 %tmp6, i32 addrspace(1)* %arg1, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}trunc_shl_vec_vec:
+; GCN-DAG: v_lshlrev_b32_e32 v{{[0-9]+}}, 3, v{{[0-9]+}}
+; GCN-DAG: v_lshlrev_b32_e32 v{{[0-9]+}}, 4, v{{[0-9]+}}
+; GCN-DAG: v_lshlrev_b32_e32 v{{[0-9]+}}, 5, v{{[0-9]+}}
+; GCN-DAG: v_lshlrev_b32_e32 v{{[0-9]+}}, 6, v{{[0-9]+}}
+; GCN-NOT: v_lshl_b64
+; GCN-NOT: v_lshlrev_b64
+define amdgpu_kernel void @trunc_shl_vec_vec(<4 x i64> addrspace(1)* %arg) {
+bb:
+  %v = load <4 x i64>, <4 x i64> addrspace(1)* %arg, align 32
+  %shl = shl <4 x i64> %v, <i64 3, i64 4, i64 5, i64 6>
+  store <4 x i64> %shl, <4 x i64> addrspace(1)* %arg, align 32
+  ret void
+}