[PATCH] bpf: set PREFERRED_DEBUGGING_TYPE to BTF_DEBUG

[David Faust <david.faust@oracle.com>]

BTF is the standard debug info used with BPF programs, so it makes sense
to default to BTF rather than DWARF.

Tested on x86_64-linux-gnu host for bpf-unknown-none target.

gcc/
	* config/bpf/bpf.h (PREFERRED_DEBUGGING_TYPE): Set to BTF_DEBUG.

gcc/testsuite/
	* gcc.target/bpf/bpf-debug-options-1.c: New test.
	* gcc.target/bpf/bpf-debug-options-2.c: Likewise.
	* gcc.target/bpf/bpf-debug-options-3.c: Likewise.
	* gcc.target/bpf/core-options-4.c: Likewise.
---
 gcc/config/bpf/bpf.h                           |  5 +++++
 .../gcc.target/bpf/bpf-debug-options-1.c       | 17 +++++++++++++++++
 .../gcc.target/bpf/bpf-debug-options-2.c       | 18 ++++++++++++++++++
 .../gcc.target/bpf/bpf-debug-options-3.c       | 14 ++++++++++++++
 gcc/testsuite/gcc.target/bpf/core-options-4.c  |  4 ++++
 5 files changed, 58 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/bpf/bpf-debug-options-1.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/bpf-debug-options-2.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/bpf-debug-options-3.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/core-options-4.c

diff --git a/gcc/config/bpf/bpf.h b/gcc/config/bpf/bpf.h
index c67e17526bf..e163fbf688d 100644
--- a/gcc/config/bpf/bpf.h
+++ b/gcc/config/bpf/bpf.h
@@ -245,6 +245,11 @@ enum reg_class
 
 /**** Debugging Info ****/
 
+/* Use BTF debug info by default.  */
+
+#undef  PREFERRED_DEBUGGING_TYPE
+#define PREFERRED_DEBUGGING_TYPE BTF_DEBUG
+
 /* In eBPF it is not possible to unwind frames. Disable CFA.  */
 
 #define DWARF2_FRAME_INFO 0
diff --git a/gcc/testsuite/gcc.target/bpf/bpf-debug-options-1.c b/gcc/testsuite/gcc.target/bpf/bpf-debug-options-1.c
new file mode 100644
index 00000000000..409466c4ead
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/bpf-debug-options-1.c
@@ -0,0 +1,17 @@
+/* Default to BTF debug info.  */
+/* { dg-do compile } */
+/* { dg-options "-g -dA" }*/
+
+struct A {
+  int x;
+  int y;
+};
+
+int
+foo (struct A *a)
+{
+  return a->x;
+}
+
+/* { dg-final { scan-assembler-not "DWARF version" } } */
+/* { dg-final { scan-assembler "btf_version" } } */
diff --git a/gcc/testsuite/gcc.target/bpf/bpf-debug-options-2.c b/gcc/testsuite/gcc.target/bpf/bpf-debug-options-2.c
new file mode 100644
index 00000000000..03bde12315b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/bpf-debug-options-2.c
@@ -0,0 +1,18 @@
+/* -g defaults to BTF, which in turn implies -mco-re.  */
+/* { dg-do compile } */
+/* { dg-options "-g -dA" }*/
+
+struct A {
+  int x;
+  int y;
+};
+
+int
+foo (struct A *a)
+{
+  return __builtin_preserve_access_index (a->x);
+}
+
+/* { dg-final { scan-assembler-not "DWARF version" } } */
+/* { dg-final { scan-assembler "btf_version" } } */
+/* { dg-final { scan-assembler "btfext_version" } } */
diff --git a/gcc/testsuite/gcc.target/bpf/bpf-debug-options-3.c b/gcc/testsuite/gcc.target/bpf/bpf-debug-options-3.c
new file mode 100644
index 00000000000..d41790e0928
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/bpf-debug-options-3.c
@@ -0,0 +1,14 @@
+/* Using -g does not incorrectly force CO-RE enabled.  */
+/* { dg-do compile } */
+/* { dg-options "-g -dA -mno-co-re" }*/
+
+struct A {
+  int x;
+  int y;
+};
+
+int
+foo (struct A *a)
+{
+  return __builtin_preserve_access_index (a->x); /* { dg-error "BPF CO-RE is required" } */
+}
diff --git a/gcc/testsuite/gcc.target/bpf/core-options-4.c b/gcc/testsuite/gcc.target/bpf/core-options-4.c
new file mode 100644
index 00000000000..fde4195da42
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/core-options-4.c
@@ -0,0 +1,4 @@
+/* -g implies BTF, -gtoggle turns it off.  CO-RE should not work.  */
+/* { dg-do compile } */
+/* { dg-options "-g -mco-re -gtoggle" } */
+/* { dg-excess-errors "BPF CO-RE requires BTF debugging information" } */
-- 
2.43.0