[InstCombine] add tests for bitcasted shuffle operand; NFC

Similar to D76844, but this is casted from wider element type.
See D77881.

llvm/test/Transforms/InstCombine/shufflevec-bitcast.ll

@@ -108,3 +108,59 @@ define <4 x i16> @splat_bitcast_operand_wider_src_elt(<2 x i32> %x) {
   %s2 = shufflevector <4 x i16> %bc, <4 x i16> undef, <4 x i32> <i32 0, i32 1, i32 0, i32 1>
   ret <4 x i16> %s2
 }
+
+define <4 x i16> @splat_bitcast_operand_wider_src_elt_uses(<2 x i32> %x) {
+; CHECK-LABEL: @splat_bitcast_operand_wider_src_elt_uses(
+; CHECK-NEXT:    [[S1:%.*]] = shufflevector <2 x i32> [[X:%.*]], <2 x i32> undef, <2 x i32> <i32 1, i32 1>
+; CHECK-NEXT:    [[BC:%.*]] = bitcast <2 x i32> [[S1]] to <4 x i16>
+; CHECK-NEXT:    call void @use(<4 x i16> [[BC]])
+; CHECK-NEXT:    [[S2:%.*]] = shufflevector <4 x i16> [[BC]], <4 x i16> undef, <4 x i32> <i32 0, i32 1, i32 0, i32 1>
+; CHECK-NEXT:    ret <4 x i16> [[S2]]
+;
+  %s1 = shufflevector <2 x i32> %x, <2 x i32> undef, <2 x i32> <i32 1, i32 1>
+  %bc = bitcast <2 x i32> %s1 to <4 x i16>
+  call void @use(<4 x i16> %bc)
+  %s2 = shufflevector <4 x i16> %bc, <4 x i16> undef, <4 x i32> <i32 0, i32 1, i32 0, i32 1>
+  ret <4 x i16> %s2
+}
+
+; Scaled mask is inverse of first mask.
+
+define <16 x i8> @shuf_bitcast_operand_wider_src(<4 x i32> %x) {
+; CHECK-LABEL: @shuf_bitcast_operand_wider_src(
+; CHECK-NEXT:    [[S1:%.*]] = shufflevector <4 x i32> [[X:%.*]], <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:    [[BC:%.*]] = bitcast <4 x i32> [[S1]] to <16 x i8>
+; CHECK-NEXT:    [[S2:%.*]] = shufflevector <16 x i8> [[BC]], <16 x i8> undef, <16 x i32> <i32 12, i32 13, i32 14, i32 15, i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7, i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    ret <16 x i8> [[S2]]
+;
+  %s1 = shufflevector <4 x i32> %x, <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+  %bc = bitcast <4 x i32> %s1 to <16 x i8>
+  %s2 = shufflevector <16 x i8> %bc, <16 x i8> undef, <16 x i32> <i32 12, i32 13, i32 14, i32 15, i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7, i32 0, i32 1, i32 2, i32 3>
+  ret <16 x i8> %s2
+}
+
+define <16 x i8> @shuf_bitcast_operand_cannot_widen(<4 x i32> %x) {
+; CHECK-LABEL: @shuf_bitcast_operand_cannot_widen(
+; CHECK-NEXT:    [[S1:%.*]] = shufflevector <4 x i32> [[X:%.*]], <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:    [[BC:%.*]] = bitcast <4 x i32> [[S1]] to <16 x i8>
+; CHECK-NEXT:    [[S2:%.*]] = shufflevector <16 x i8> [[BC]], <16 x i8> undef, <16 x i32> <i32 12, i32 13, i32 12, i32 13, i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7, i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    ret <16 x i8> [[S2]]
+;
+  %s1 = shufflevector <4 x i32> %x, <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+  %bc = bitcast <4 x i32> %s1 to <16 x i8>
+  %s2 = shufflevector <16 x i8> %bc, <16 x i8> undef, <16 x i32> <i32 12, i32 13, i32 12, i32 13, i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7, i32 0, i32 1, i32 2, i32 3>
+  ret <16 x i8> %s2
+}
+
+define <16 x i8> @shuf_bitcast_operand_cannot_widen_undef(<4 x i32> %x) {
+; CHECK-LABEL: @shuf_bitcast_operand_cannot_widen_undef(
+; CHECK-NEXT:    [[S1:%.*]] = shufflevector <4 x i32> [[X:%.*]], <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+; CHECK-NEXT:    [[BC:%.*]] = bitcast <4 x i32> [[S1]] to <16 x i8>
+; CHECK-NEXT:    [[S2:%.*]] = shufflevector <16 x i8> [[BC]], <16 x i8> undef, <16 x i32> <i32 12, i32 undef, i32 14, i32 15, i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7, i32 0, i32 1, i32 2, i32 3>
+; CHECK-NEXT:    ret <16 x i8> [[S2]]
+;
+  %s1 = shufflevector <4 x i32> %x, <4 x i32> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
+  %bc = bitcast <4 x i32> %s1 to <16 x i8>
+  %s2 = shufflevector <16 x i8> %bc, <16 x i8> undef, <16 x i32> <i32 12, i32 undef, i32 14, i32 15, i32 8, i32 9, i32 10, i32 11, i32 4, i32 5, i32 6, i32 7, i32 0, i32 1, i32 2, i32 3>
+  ret <16 x i8> %s2
+}