bpf: define BPF feature pre-processor macros

This commit makes the BPF backend to define the following macros for
c-family languages:

  __BPF_CPU_VERSION__

    This is a numeric value identifying the version of the BPF "cpu"
    for which GCC is generating code.

  __BPF_FEATURE_ALU32
  __BPF_FEATURE_JMP32
  __BPF_FEATURE_JMP_EXT
  __BPF_FEATURE_BSWAP
  __BPF_FEATURE_SDIV_SMOD
  __BPF_FEATURE_MOVSX
  __BPF_FEATURE_LDSX
  __BPF_FEATURE_GOTOL
  __BPF_FEATURE_ST

    These are defines if the corresponding "feature" is enabled.  The
    features are implicitly enabled by the BPF CPU version enabled,
    and most of them can also be enabled/disabled using
    target-specific -m[no-]FEATURE command line switches.

Note that this patch moves the definition of bpf_target_macros, that
implements TARGET_CPU_CPP_BUILTINS in the BPF backend, to a bpf-c.cc
file.  This is because we are now using facilities from c-family/* and
these features are not available in compilers like lto1.

A couple of tests are also added.
Tested in target bpf-unknown-none-gcc and host x86_64-linux-gnu.
No regressions.

gcc/ChangeLog

	* config.gcc: Add bpf-c.o as a target object for C and C++.
	* config/bpf/bpf.cc (bpf_target_macros): Move to bpf-c.cc.
	* config/bpf/bpf-c.cc: New file.
	(bpf_target_macros): Move from bpf.cc and define BPF CPU
	feature	macros.
	* config/bpf/t-bpf: Add rules to build bpf-c.o.

gcc/testsuite/ChangeLog

	* gcc.target/bpf/feature-macro-1.c: New test.
	* gcc.target/bpf/feature-macro-2.c: Likewise.

3 files changed, 92 insertions, 17 deletions

diff --git a/gcc/config/bpf/bpf-c.cc b/gcc/config/bpf/bpf-c.cc
new file mode 100644
index 0000000..f12f062
--- /dev/null
+++ b/gcc/config/bpf/bpf-c.cc
@@ -0,0 +1,88 @@
+/* BPF-specific code for C family languages.
+   Copyright (C) 2024 Free Software Foundation, Inc.
+   Contributed by Oracle Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#define IN_TARGET_CODE 1
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "c-family/c-common.h"
+#include "cpplib.h"
+
+/* Define target-specific CPP macros.  This function in used in the
+   definition of TARGET_CPU_CPP_BUILTINS in bpf.h */
+
+#define builtin_define(TXT) cpp_define (pfile, TXT)
+
+void
+bpf_target_macros (cpp_reader *pfile)
+{
+  builtin_define ("__BPF__");
+  builtin_define ("__bpf__");
+
+  if (TARGET_BIG_ENDIAN)
+    builtin_define ("__BPF_BIG_ENDIAN__");
+  else
+    builtin_define ("__BPF_LITTLE_ENDIAN__");
+
+  switch (bpf_isa)
+    {
+    case ISA_V1:
+      builtin_define_with_int_value ("__BPF_CPU_VERSION__", 1);
+      break;
+    case ISA_V2:
+      builtin_define_with_int_value ("__BPF_CPU_VERSION__", 2);
+      break;
+    case ISA_V3:
+      builtin_define_with_int_value ("__BPF_CPU_VERSION__", 3);
+      break;
+    case ISA_V4:
+      builtin_define_with_int_value ("__BPF_CPU_VERSION__", 4);
+      break;
+    default:
+      gcc_unreachable ();
+      break;
+    }
+
+  /* Different BPF CPU versions support different features.  Some of
+     them can be enabled/disabled explicitly.  */
+  if (bpf_has_alu32)
+    builtin_define ("__BPF_FEATURE_ALU32");
+  if (bpf_has_jmp32)
+    builtin_define ("__BPF_FEATURE_JMP32");
+  if (bpf_has_jmpext)
+    builtin_define ("__BPF_FEATURE_JMP_EXT");
+  if (bpf_has_bswap)
+    builtin_define ("__BPF_FEATURE_BSWAP");
+  if (bpf_has_sdiv)
+    builtin_define ("__BPF_FEATURE_SDIV_SMOD");
+  if (bpf_has_smov)
+    builtin_define ("__BPF_FEATURE_MOVSX");
+
+  /* Other CPU features can only be enabled/disabled generically by
+     selecting the corresponding CPU version.  */
+  if (bpf_isa >= ISA_V4)
+    {
+      builtin_define ("__BPF_FEATURE_LDSX");
+      builtin_define ("__BPF_FEATURE_GOTOL");
+      builtin_define ("__BPF_FEATURE_ST");
+    }
+}
diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
index d9141dd..98fb755 100644
--- a/gcc/config/bpf/bpf.cc
+++ b/gcc/config/bpf/bpf.cc
@@ -284,23 +284,6 @@ bpf_file_end (void)
 #undef TARGET_ASM_FILE_END
 #define TARGET_ASM_FILE_END bpf_file_end
 
-/* Define target-specific CPP macros.  This function in used in the
-   definition of TARGET_CPU_CPP_BUILTINS in bpf.h */
-
-#define builtin_define(TXT) cpp_define (pfile, TXT)
-
-void
-bpf_target_macros (cpp_reader *pfile)
-{
-  builtin_define ("__BPF__");
-  builtin_define ("__bpf__");
-
-  if (TARGET_BIG_ENDIAN)
-    builtin_define ("__BPF_BIG_ENDIAN__");
-  else
-    builtin_define ("__BPF_LITTLE_ENDIAN__");
-}
-
 /* Return an RTX representing the place where a function returns or
    receives a value of data type RET_TYPE, a tree node representing a
    data type.  */
diff --git a/gcc/config/bpf/t-bpf b/gcc/config/bpf/t-bpf
index dc50332..2facccb 100644
--- a/gcc/config/bpf/t-bpf
+++ b/gcc/config/bpf/t-bpf
@@ -1,6 +1,10 @@
 
 TM_H += $(srcdir)/config/bpf/btfext-out.h $(srcdir)/config/bpf/core-builtins.h
 
+bpf-c.o: $(srcdir)/config/bpf/bpf-c.cc
+	$(COMPILE) $<
+	$(POSTCOMPILE)
+
 btfext-out.o: $(srcdir)/config/bpf/btfext-out.cc
 	$(COMPILE) $<
 	$(POSTCOMPILE)