[gcc r14-5925] This patch enables errors when external calls are created.

[gcc r14-5925] This patch enables errors when external calls are created.

[Cupertino Miranda]

https://gcc.gnu.org/g:faf5b148588bd7fbb60ec669aefa704044037cdc

commit r14-5925-gfaf5b148588bd7fbb60ec669aefa704044037cdc
Author: Cupertino Miranda <cupertino.miranda@oracle.com>
Date:   Thu Nov 23 22:28:01 2023 +0000

    This patch enables errors when external calls are created.
    
    When architectural limitations or usage of builtins implies the compiler
    to create function calls to external libraries that implement the
    functionality, GCC will now report an error claiming that this function
    calls are not compatible with eBPF target.
    Examples of those are the usage of __builtin_memmove and a sign division
    in BPF ISA v3 or below that will require to call __divdi3.
    This is currently an eBPF limitation which does not support linking of
    object files but rather "raw" non linked ones. Those object files are
    loaded and relocated by libbpf and the kernel.
    
    gcc/ChangeLog:
            * config/bpf/bpf.cc (bpf_output_call): Report error in case the
            function call is for a builtin.
            (bpf_external_libcall): Added target hook to detect and report
            error when other external calls that are not builtins.
    
    gcc/testsuite/ChangeLog:
            * gcc.target/bpf/atomic-cmpxchg-2.c: Adapted.
            * gcc.target/bpf/atomic-fetch-op-3.c: Adapted.
            * gcc.target/bpf/atomic-op-3.c: Adapted.
            * gcc.target/bpf/atomic-xchg-2.c: Adapted.
            * gcc.target/bpf/diag-sdiv.c: Adapted.
            * gcc.target/bpf/diag-smod.c: Adapted.

Diff:
---
 gcc/config/bpf/bpf.cc                            | 21 +++++++++++++++++++++
 gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c  |  2 +-
 gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c |  2 +-
 gcc/testsuite/gcc.target/bpf/atomic-op-3.c       |  2 +-
 gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c     |  2 +-
 gcc/testsuite/gcc.target/bpf/diag-sdiv.c         |  2 +-
 gcc/testsuite/gcc.target/bpf/diag-smod.c         |  2 +-
 7 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/gcc/config/bpf/bpf.cc b/gcc/config/bpf/bpf.cc
index 4bfba289546..80108018c24 100644
--- a/gcc/config/bpf/bpf.cc
+++ b/gcc/config/bpf/bpf.cc
@@ -746,6 +746,15 @@ bpf_output_call (rtx target)
 	    xops[0] = GEN_INT (TREE_INT_CST_LOW (TREE_VALUE (attr_args)));
 	    output_asm_insn ("call\t%0", xops);
 	  }
+	else if (fndecl_built_in_p (decl))
+	  {
+	    /* For now lets report this as an error while we are not able to
+	       link eBPF object files.  In particular with libgcc.  */
+	    tree name = DECL_NAME (decl);
+	    error ("call to external builtin %s in function, which is not supported by "
+		   "eBPF", name != NULL_TREE ? IDENTIFIER_POINTER (name) : "(anon)");
+	    output_asm_insn ("call 0", NULL);
+	  }
 	else
 	  output_asm_insn ("call\t%0", &target);
 
@@ -765,6 +774,18 @@ bpf_output_call (rtx target)
   return "";
 }
 
+static void
+bpf_external_libcall (rtx fun)
+{
+  tree decl = SYMBOL_REF_DECL (fun);
+  tree name = DECL_NAME (decl);
+  error ("call to external libcall %s in function, which is not supported by "
+	 "eBPF", name != NULL_TREE ? IDENTIFIER_POINTER (name) : "(anon)");
+}
+
+#undef  TARGET_ASM_EXTERNAL_LIBCALL
+#define TARGET_ASM_EXTERNAL_LIBCALL bpf_external_libcall
+
 /* Print register name according to assembly dialect.  In normal
    syntax registers are printed like %rN where N is the register
    number.
diff --git a/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c b/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c
index 4036570ac60..fec720584e4 100644
--- a/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c
+++ b/gcc/testsuite/gcc.target/bpf/atomic-cmpxchg-2.c
@@ -6,7 +6,7 @@ foo (int *p, int *expected, int desired)
 {
   return __atomic_compare_exchange (p, expected, &desired, 0,
 				    __ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
-}
+} /* { dg-error "call to external builtin" } */
 
 int
 foo64 (long *p, long *expected, long desired)
diff --git a/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c b/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c
index 044a2f76474..ea1b8e48928 100644
--- a/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c
+++ b/gcc/testsuite/gcc.target/bpf/atomic-fetch-op-3.c
@@ -9,7 +9,7 @@ long
 test_atomic_fetch_add (long x)
 {
   return __atomic_fetch_add (&val, x, __ATOMIC_ACQUIRE);
-}
+} /* { dg-error "call to external builtin" } */
 
 long
 test_atomic_fetch_sub (long x)
diff --git a/gcc/testsuite/gcc.target/bpf/atomic-op-3.c b/gcc/testsuite/gcc.target/bpf/atomic-op-3.c
index b2ce2892634..fefafd6b748 100644
--- a/gcc/testsuite/gcc.target/bpf/atomic-op-3.c
+++ b/gcc/testsuite/gcc.target/bpf/atomic-op-3.c
@@ -20,7 +20,7 @@ void
 test_atomic_and (int x)
 {
   __atomic_and_fetch (&val, x, __ATOMIC_ACQUIRE);
-}
+} /* { dg-error "call to external builtin" } */
 
 void
 test_atomic_nand (int x)
diff --git a/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c b/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c
index 3b6324e966b..eab695bf388 100644
--- a/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c
+++ b/gcc/testsuite/gcc.target/bpf/atomic-xchg-2.c
@@ -7,7 +7,7 @@ int foo (int *p, int *new)
   int old;
   __atomic_exchange (p, new, &old, __ATOMIC_RELAXED);
   return old;
-}
+} /* { dg-error "call to external builtin" } */
 
 int foo64 (long *p, long *new)
 {
diff --git a/gcc/testsuite/gcc.target/bpf/diag-sdiv.c b/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
index c48bbf03df9..c3332558e7d 100644
--- a/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
+++ b/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
@@ -7,6 +7,6 @@ foo ()
 {
   signed int x = 5;
   signed int y = 2;
-  signed int z = x / y;
+  signed int z = x / y; /* { dg-error "call to external libcall" } */
 }
 /* { dg-final { scan-assembler-not "sdiv(32)?\t%r" } } */
diff --git a/gcc/testsuite/gcc.target/bpf/diag-smod.c b/gcc/testsuite/gcc.target/bpf/diag-smod.c
index d3df308217f..25bcb1e4ffd 100644
--- a/gcc/testsuite/gcc.target/bpf/diag-smod.c
+++ b/gcc/testsuite/gcc.target/bpf/diag-smod.c
@@ -7,6 +7,6 @@ foo ()
 {
   signed int x = 5;
   signed int y = 2;
-  signed int z = x % y;
+  signed int z = x % y; /* { dg-error "call to external libcall" } */
 }
 /* { dg-final { scan-assembler-not "smod(32)?\t%r" } } */