bpf: add tests for CO-RE and BTF tag interaction

Add a couple of tests to ensure that BTF type/decl tags do not interfere
with generation of BPF CO-RE relocations.

gcc/testsuite/
	* gcc.target/bpf/core-btf-tag-1.c: New test.
	* gcc.target/bpf/core-btf-tag-2.c: New test.

Author: dafaust

gcc/testsuite/gcc.target/bpf/core-btf-tag-1.c

@@ -0,0 +1,23 @@
+/* Test that BTF type tags do not interfere with CO-RE relocations.  */
+
+/* { dg-do compile } */
+/* { dg-options "-gbtf -dA -mco-re" } */
+
+struct bpf_cpumask {
+  int i;
+  char c;
+} __attribute__((preserve_access_index));
+
+struct kptr_nested {
+	struct bpf_cpumask * __attribute__((btf_type_tag("kptr"))) mask;
+} __attribute__((preserve_access_index));
+
+void foo (struct kptr_nested *nested)
+{
+  if (nested && nested->mask)
+    nested->mask->i = 5;
+}
+
+/* { dg-final { scan-assembler-times "bpfcr_insn" 3 } } */
+/* { dg-final { scan-assembler-times "bpfcr_type \\(struct" 3 } } */
+/* { dg-final { scan-assembler-times "bpfcr_astr_off \\(\"0:0\"\\)" 3 } } */

gcc/testsuite/gcc.target/bpf/core-btf-tag-2.c

@@ -0,0 +1,23 @@
+/* Test that BTF decl tags do not interfere with CO-RE relocations.  */
+
+/* { dg-do compile } */
+/* { dg-options "-gbtf -dA -mco-re" } */
+
+struct bpf_cpumask {
+  int i;
+  char c;
+} __attribute__((preserve_access_index));
+
+struct kptr_nested {
+	struct bpf_cpumask * mask __attribute__((btf_decl_tag ("decltag")));
+} __attribute__((preserve_access_index));
+
+void foo (struct kptr_nested *nested __attribute__((btf_decl_tag ("foo"))))
+{
+  if (nested && nested->mask)
+    nested->mask->i = 5;
+}
+
+/* { dg-final { scan-assembler-times "bpfcr_insn" 3 } } */
+/* { dg-final { scan-assembler-times "bpfcr_type \\(struct" 3 } } */
+/* { dg-final { scan-assembler-times "bpfcr_astr_off \\(\"0:0\"\\)" 3 } } */