[X86] Add test for `~x & x` -> `0` in DAG Lowering; NFC

[goldstein.w.n]

Rebase

[RKSimon]

LGTM - but maybe name this combine-andn.ll ? Or just add them to combine-and.ll?

[goldstein.w.n]

Move and tests, add add tests

[goldstein.w.n]

In D145142#4164133, @RKSimon wrote:

LGTM - but maybe name this combine-andn.ll ? Or just add them to combine-and.ll?

Done (also updated with ~x + x cases in combine-add.ll as we are missing combine there as well.

[goldstein.w.n]

Rebase

llvm/test/CodeGen/X86/andn-x-x.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-pc-linux-gnu | FileCheck %s
+
+define <2 x i64> @andnp_xx(<2 x i64> %v0) nounwind {
+; CHECK-LABEL: andnp_xx:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    andnps %xmm0, %xmm0
+; CHECK-NEXT:    retq
+  %x = xor <2 x i64> %v0, <i64 -1, i64 -1>
+  %y = and <2 x i64> %v0, %x
+  ret <2 x i64> %y
+}
+
+define <2 x i64> @andnp_xx_2(<2 x i64> %v0) nounwind {
+; CHECK-LABEL: andnp_xx_2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    andnps %xmm0, %xmm0
+; CHECK-NEXT:    retq
+  %x = xor <2 x i64> %v0, <i64 -1, i64 -1>
+  %y = and <2 x i64> %x, %v0
+  ret <2 x i64> %y
+}
+
+define i64 @andn_xx(i64 %v0) nounwind {
+; CHECK-LABEL: andn_xx:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movq %rdi, %rax
+; CHECK-NEXT:    notq %rax
+; CHECK-NEXT:    andq %rdi, %rax
+; CHECK-NEXT:    retq
+  %x = xor i64 %v0, -1
+  %y = and i64 %v0, %x
+  ret i64 %y
+}
+
+define i64 @andn_xx_2(i64 %v0) nounwind {
+; CHECK-LABEL: andn_xx_2:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movq %rdi, %rax
+; CHECK-NEXT:    notq %rax
+; CHECK-NEXT:    andq %rdi, %rax
+; CHECK-NEXT:    retq
+  %x = xor i64 %v0, -1
+  %y = and i64 %x, %v0
+  ret i64 %y
+}