Index: llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
@@ -1540,8 +1540,17 @@
     // The insert is to the LSB end of the vector (depends on endian).
     // That's all we need.
   } else {
-    // TODO: Look through a shift-right and translate the insert index.
-    return nullptr;
+    // If not, we must match a right-shift to translate the insert index.
+    uint64_t ShiftC;
+    if (!match(T, m_OneUse(m_LShr(m_Value(X), m_ConstantInt(ShiftC)))))
+      return nullptr;
+
+    // Check the shift amount to see if this can be folded to a select-shuffle.
+    // Big endian has MSB at vector index 0, so the insert index is flipped.
+    if (IsBigEndian && (NumEltsInScalar - 1 - IndexC) * VecEltWidth != ShiftC)
+      return nullptr;
+    if (!IsBigEndian && IndexC * VecEltWidth != ShiftC)
+      return nullptr;
   }
 
   // Bitcast the scalar to a vector type with the destination element type.
Index: llvm/test/Transforms/InstCombine/insert-trunc.ll
===================================================================
--- llvm/test/Transforms/InstCombine/insert-trunc.ll
+++ llvm/test/Transforms/InstCombine/insert-trunc.ll
@@ -143,11 +143,16 @@
 }
 
 define <4 x i16> @lshr_same_length_poison_basevec_le(i64 %x) {
-; ALL-LABEL: @lshr_same_length_poison_basevec_le(
-; ALL-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 32
-; ALL-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
-; ALL-NEXT:    [[R:%.*]] = insertelement <4 x i16> poison, i16 [[T]], i64 2
-; ALL-NEXT:    ret <4 x i16> [[R]]
+; BE-LABEL: @lshr_same_length_poison_basevec_le(
+; BE-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 32
+; BE-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
+; BE-NEXT:    [[R:%.*]] = insertelement <4 x i16> poison, i16 [[T]], i64 2
+; BE-NEXT:    ret <4 x i16> [[R]]
+;
+; LE-LABEL: @lshr_same_length_poison_basevec_le(
+; LE-NEXT:    [[VEC_X:%.*]] = bitcast i64 [[X:%.*]] to <4 x i16>
+; LE-NEXT:    [[R:%.*]] = shufflevector <4 x i16> [[VEC_X]], <4 x i16> poison, <4 x i32> <i32 undef, i32 undef, i32 2, i32 undef>
+; LE-NEXT:    ret <4 x i16> [[R]]
 ;
   %s = lshr i64 %x, 32
   %t = trunc i64 %s to i16
@@ -156,11 +161,16 @@
 }
 
 define <4 x i16> @lshr_same_length_poison_basevec_be(i64 %x) {
-; ALL-LABEL: @lshr_same_length_poison_basevec_be(
-; ALL-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 32
-; ALL-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
-; ALL-NEXT:    [[R:%.*]] = insertelement <4 x i16> poison, i16 [[T]], i64 1
-; ALL-NEXT:    ret <4 x i16> [[R]]
+; BE-LABEL: @lshr_same_length_poison_basevec_be(
+; BE-NEXT:    [[VEC_X:%.*]] = bitcast i64 [[X:%.*]] to <4 x i16>
+; BE-NEXT:    [[R:%.*]] = shufflevector <4 x i16> [[VEC_X]], <4 x i16> poison, <4 x i32> <i32 undef, i32 1, i32 undef, i32 undef>
+; BE-NEXT:    ret <4 x i16> [[R]]
+;
+; LE-LABEL: @lshr_same_length_poison_basevec_be(
+; LE-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 32
+; LE-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
+; LE-NEXT:    [[R:%.*]] = insertelement <4 x i16> poison, i16 [[T]], i64 1
+; LE-NEXT:    ret <4 x i16> [[R]]
 ;
   %s = lshr i64 %x, 32
   %t = trunc i64 %s to i16
@@ -170,9 +180,8 @@
 
 define <4 x i16> @lshr_same_length_poison_basevec_both_endian(i64 %x) {
 ; BE-LABEL: @lshr_same_length_poison_basevec_both_endian(
-; BE-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 48
-; BE-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
-; BE-NEXT:    [[R:%.*]] = insertelement <4 x i16> poison, i16 [[T]], i64 0
+; BE-NEXT:    [[VEC_X:%.*]] = bitcast i64 [[X:%.*]] to <4 x i16>
+; BE-NEXT:    [[R:%.*]] = shufflevector <4 x i16> [[VEC_X]], <4 x i16> poison, <4 x i32> <i32 0, i32 undef, i32 undef, i32 undef>
 ; BE-NEXT:    ret <4 x i16> [[R]]
 ;
 ; LE-LABEL: @lshr_same_length_poison_basevec_both_endian(
@@ -208,9 +217,8 @@
 ; BE-NEXT:    ret <8 x i16> [[R]]
 ;
 ; LE-LABEL: @lshr_longer_length_poison_basevec_le(
-; LE-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 48
-; LE-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
-; LE-NEXT:    [[R:%.*]] = insertelement <8 x i16> poison, i16 [[T]], i64 3
+; LE-NEXT:    [[VEC_X:%.*]] = bitcast i64 [[X:%.*]] to <4 x i16>
+; LE-NEXT:    [[R:%.*]] = shufflevector <4 x i16> [[VEC_X]], <4 x i16> poison, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 3, i32 undef, i32 undef, i32 undef, i32 undef>
 ; LE-NEXT:    ret <8 x i16> [[R]]
 ;
   %s = lshr i64 %x, 48
@@ -220,11 +228,16 @@
 }
 
 define <8 x i16> @lshr_longer_length_poison_basevec_be(i64 %x) {
-; ALL-LABEL: @lshr_longer_length_poison_basevec_be(
-; ALL-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 32
-; ALL-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
-; ALL-NEXT:    [[R:%.*]] = insertelement <8 x i16> poison, i16 [[T]], i64 1
-; ALL-NEXT:    ret <8 x i16> [[R]]
+; BE-LABEL: @lshr_longer_length_poison_basevec_be(
+; BE-NEXT:    [[VEC_X:%.*]] = bitcast i64 [[X:%.*]] to <4 x i16>
+; BE-NEXT:    [[R:%.*]] = shufflevector <4 x i16> [[VEC_X]], <4 x i16> poison, <8 x i32> <i32 undef, i32 1, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
+; BE-NEXT:    ret <8 x i16> [[R]]
+;
+; LE-LABEL: @lshr_longer_length_poison_basevec_be(
+; LE-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 32
+; LE-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
+; LE-NEXT:    [[R:%.*]] = insertelement <8 x i16> poison, i16 [[T]], i64 1
+; LE-NEXT:    ret <8 x i16> [[R]]
 ;
   %s = lshr i64 %x, 32
   %t = trunc i64 %s to i16
@@ -246,11 +259,16 @@
 }
 
 define <2 x i16> @lshr_shorter_length_poison_basevec_le(i64 %x) {
-; ALL-LABEL: @lshr_shorter_length_poison_basevec_le(
-; ALL-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 16
-; ALL-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
-; ALL-NEXT:    [[R:%.*]] = insertelement <2 x i16> poison, i16 [[T]], i64 1
-; ALL-NEXT:    ret <2 x i16> [[R]]
+; BE-LABEL: @lshr_shorter_length_poison_basevec_le(
+; BE-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 16
+; BE-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i16
+; BE-NEXT:    [[R:%.*]] = insertelement <2 x i16> poison, i16 [[T]], i64 1
+; BE-NEXT:    ret <2 x i16> [[R]]
+;
+; LE-LABEL: @lshr_shorter_length_poison_basevec_le(
+; LE-NEXT:    [[VEC_X:%.*]] = bitcast i64 [[X:%.*]] to <4 x i16>
+; LE-NEXT:    [[R:%.*]] = shufflevector <4 x i16> [[VEC_X]], <4 x i16> poison, <2 x i32> <i32 undef, i32 1>
+; LE-NEXT:    ret <2 x i16> [[R]]
 ;
   %s = lshr i64 %x, 16
   %t = trunc i64 %s to i16
@@ -259,11 +277,16 @@
 }
 
 define <4 x i8> @lshr_shorter_length_poison_basevec_be(i64 %x) {
-; ALL-LABEL: @lshr_shorter_length_poison_basevec_be(
-; ALL-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 40
-; ALL-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i8
-; ALL-NEXT:    [[R:%.*]] = insertelement <4 x i8> poison, i8 [[T]], i64 2
-; ALL-NEXT:    ret <4 x i8> [[R]]
+; BE-LABEL: @lshr_shorter_length_poison_basevec_be(
+; BE-NEXT:    [[VEC_X:%.*]] = bitcast i64 [[X:%.*]] to <8 x i8>
+; BE-NEXT:    [[R:%.*]] = shufflevector <8 x i8> [[VEC_X]], <8 x i8> poison, <4 x i32> <i32 undef, i32 undef, i32 2, i32 undef>
+; BE-NEXT:    ret <4 x i8> [[R]]
+;
+; LE-LABEL: @lshr_shorter_length_poison_basevec_be(
+; LE-NEXT:    [[S:%.*]] = lshr i64 [[X:%.*]], 40
+; LE-NEXT:    [[T:%.*]] = trunc i64 [[S]] to i8
+; LE-NEXT:    [[R:%.*]] = insertelement <4 x i8> poison, i8 [[T]], i64 2
+; LE-NEXT:    ret <4 x i8> [[R]]
 ;
   %s = lshr i64 %x, 40
   %t = trunc i64 %s to i8