[PATCH] Add TARGET_IFUNC_REF_LOCAL_OK

H.J. Lu hjl.tools@gmail.com
Sun Jun 20 02:10:35 GMT 2021


1. On some targets, like PowerPC, reference to ifunc function resolver
must be non-local so that compiler will properly emit PLT call.  Add
TARGET_IFUNC_REF_LOCAL_OK to allow binding indirect function resolver
locally for targets which don't require special PLT call sequence.
2. Add ix86_call_use_plt_p to call local ifunc function resolvers via
PLT.

gcc/

	PR target/51469
	PR target/83782
	* target.def (ifunc_ref_local_ok): Add a target hook.
	* varasm.c (default_binds_local_p_3): Force indirect function
	resolver non-local only if targetm.ifunc_ref_local_ok returns
	false.
	* config/i386/i386-expand.c (ix86_expand_call): Call
	ix86_call_use_plt_p to check if PLT should be used.
	* config/i386/i386-protos.h (ix86_call_use_plt_p): New.
	* config/i386/i386.c (output_pic_addr_const): Call
	ix86_call_use_plt_p to check if "@PLT" is needed.
	(ix86_call_use_plt_p): New.
	(TARGET_IFUNC_REF_LOCAL_OK): New.
	* doc/tm.texi.in: Add TARGET_IFUNC_REF_LOCAL_OK.
	* doc/tm.texi: Regenerated.

gcc/testsuite/

	PR target/51469
	PR target/83782
	* gcc.target/i386/pr83782-1.c: New test.
	* gcc.target/i386/pr83782-2.c: Likewise.
---
 gcc/config/i386/i386-expand.c             |  2 +-
 gcc/config/i386/i386-protos.h             |  1 +
 gcc/config/i386/i386.c                    | 25 +++++++++++++++++++++-
 gcc/doc/tm.texi                           |  5 +++++
 gcc/doc/tm.texi.in                        |  2 ++
 gcc/target.def                            |  8 +++++++
 gcc/testsuite/gcc.target/i386/pr83782-1.c | 26 +++++++++++++++++++++++
 gcc/testsuite/gcc.target/i386/pr83782-2.c | 26 +++++++++++++++++++++++
 gcc/varasm.c                              |  3 ++-
 9 files changed, 95 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr83782-1.c
 create mode 100644 gcc/testsuite/gcc.target/i386/pr83782-2.c

diff --git a/gcc/config/i386/i386-expand.c b/gcc/config/i386/i386-expand.c
index 8f4e4e4d884..229a765cb40 100644
--- a/gcc/config/i386/i386-expand.c
+++ b/gcc/config/i386/i386-expand.c
@@ -8184,7 +8184,7 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx callarg1,
       rtx addr = XEXP (fnaddr, 0);
       if (flag_pic
 	  && GET_CODE (addr) == SYMBOL_REF
-	  && !SYMBOL_REF_LOCAL_P (addr))
+	  && ix86_call_use_plt_p (addr))
 	{
 	  if (flag_plt
 	      && (SYMBOL_REF_DECL (addr) == NULL_TREE
diff --git a/gcc/config/i386/i386-protos.h b/gcc/config/i386/i386-protos.h
index e6ac9390777..2d1cd07a215 100644
--- a/gcc/config/i386/i386-protos.h
+++ b/gcc/config/i386/i386-protos.h
@@ -152,6 +152,7 @@ extern void ix86_expand_sse_movcc (rtx, rtx, rtx, rtx);
 extern void ix86_expand_sse_unpack (rtx, rtx, bool, bool);
 extern bool ix86_expand_int_addcc (rtx[]);
 extern rtx_insn *ix86_expand_call (rtx, rtx, rtx, rtx, rtx, bool);
+extern bool ix86_call_use_plt_p (rtx);
 extern void ix86_split_call_vzeroupper (rtx, rtx);
 extern void x86_initialize_trampoline (rtx, rtx, rtx);
 extern rtx ix86_zero_extend_to_Pmode (rtx);
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 7d0d4143bca..731a516b516 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -11971,7 +11971,7 @@ output_pic_addr_const (FILE *file, rtx x, int code)
 	  assemble_name (file, name);
 	}
       if (!TARGET_MACHO && !(TARGET_64BIT && TARGET_PECOFF)
-	  && code == 'P' && ! SYMBOL_REF_LOCAL_P (x))
+	  && code == 'P' && ix86_call_use_plt_p (x))
 	fputs ("@PLT", file);
       break;
 
@@ -15678,6 +15678,26 @@ ix86_zero_extend_to_Pmode (rtx exp)
   return force_reg (Pmode, convert_to_mode (Pmode, exp, 1));
 }
 
+/* Return true if the function is called via PLT.   */
+
+bool
+ix86_call_use_plt_p (rtx call_op)
+{
+  if (SYMBOL_REF_LOCAL_P (call_op))
+    {
+      if (SYMBOL_REF_DECL (call_op))
+	{
+	  /* NB: All ifunc functions must be called via PLT.  */
+	  cgraph_node *node
+	    = cgraph_node::get (SYMBOL_REF_DECL (call_op));
+	  if (node && node->ifunc_resolver)
+	    return true;
+	}
+      return false;
+    }
+  return true;
+}
+
 /* Return true if the function being called was marked with attribute
    "noplt" or using -fno-plt and we are compiling for non-PIC.  We need
    to handle the non-PIC case in the backend because there is no easy
@@ -24016,6 +24036,9 @@ ix86_run_selftests (void)
 #define TARGET_GET_MULTILIB_ABI_NAME \
   ix86_get_multilib_abi_name
 
+#undef TARGET_IFUNC_REF_LOCAL_OK
+#define TARGET_IFUNC_REF_LOCAL_OK hook_bool_void_true
+
 static bool ix86_libc_has_fast_function (int fcode ATTRIBUTE_UNUSED)
 {
 #ifdef OPTION_GLIBC
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 2a41ae5fba1..d327af03c80 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -12346,6 +12346,11 @@ The support includes the assembler, linker and dynamic linker.
 The default value of this hook is based on target's libc.
 @end deftypefn
 
+@deftypefn {Target Hook} bool TARGET_IFUNC_REF_LOCAL_OK (void)
+Return true if it is OK to reference indirect function resolvers
+locally.  The default is to return false.
+@end deftypefn
+
 @deftypefn {Target Hook} {unsigned int} TARGET_ATOMIC_ALIGN_FOR_MODE (machine_mode @var{mode})
 If defined, this function returns an appropriate alignment in bits for an
 atomic object of machine_mode @var{mode}.  If 0 is returned then the
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index f881cdabe9e..cc6f7994cb1 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -8073,6 +8073,8 @@ and the associated definitions of those functions.
 
 @hook TARGET_HAS_IFUNC_P
 
+@hook TARGET_IFUNC_REF_LOCAL_OK
+
 @hook TARGET_ATOMIC_ALIGN_FOR_MODE
 
 @hook TARGET_ATOMIC_ASSIGN_EXPAND_FENV
diff --git a/gcc/target.def b/gcc/target.def
index c009671c583..2c8aa90afac 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -2990,6 +2990,14 @@ The default value of this hook is based on target's libc.",
  bool, (void),
  default_has_ifunc_p)
 
+/* True if it is OK to reference indirect function resolvers locally.  */
+DEFHOOK
+(ifunc_ref_local_ok,
+ "Return true if it is OK to reference indirect function resolvers\n\
+locally.  The default is to return false.",
+ bool, (void),
+ hook_bool_void_false)
+
 /* True if it is OK to do sibling call optimization for the specified
    call expression EXP.  DECL will be the called function, or NULL if
    this is an indirect call.  */
diff --git a/gcc/testsuite/gcc.target/i386/pr83782-1.c b/gcc/testsuite/gcc.target/i386/pr83782-1.c
new file mode 100644
index 00000000000..f4c7370142a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr83782-1.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-require-ifunc "" } */
+/* { dg-options "-O2 -fpic" } */
+
+static void
+my_foo (void)
+{
+}
+
+static void (*resolve_foo (void)) (void)
+{
+  return my_foo;
+}
+
+extern void foo (void) __attribute__((ifunc("resolve_foo"), visibility("hidden")));
+
+void *
+bar(void)
+{
+  return foo;
+}
+
+/* { dg-final { scan-assembler {leal[ \t]foo@GOTOFF\(%[^,]*\),[ \t]%eax} { target ia32 } } } */
+/* { dg-final { scan-assembler {leaq[ \t]foo\(%rip\),[ \t]%rax} { target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-not "foo@GOT\\\(" { target ia32 } } } */
+/* { dg-final { scan-assembler-not "foo@GOTPCREL\\\(" { target { ! ia32 } } } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr83782-2.c b/gcc/testsuite/gcc.target/i386/pr83782-2.c
new file mode 100644
index 00000000000..6c6528fff46
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr83782-2.c
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-require-ifunc "" } */
+/* { dg-options "-O2 -fpic" } */
+
+static void
+my_foo (void)
+{
+}
+
+static void (*resolve_foo (void)) (void)
+{
+  return my_foo;
+}
+
+static void foo (void) __attribute__((ifunc("resolve_foo")));
+
+void *
+bar(void)
+{
+  return foo;
+}
+
+/* { dg-final { scan-assembler {leal[ \t]foo@GOTOFF\(%[^,]*\),[ \t]%eax} { target ia32 } } } */
+/* { dg-final { scan-assembler {leaq[ \t]foo\(%rip\),[ \t]%rax} { target { ! ia32 } } } } */
+/* { dg-final { scan-assembler-not "foo@GOT\\\(" { target ia32 } } } */
+/* { dg-final { scan-assembler-not "foo@GOTPCREL\\\(" { target { ! ia32 } } } } */
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 53cf6dea3f3..0cba7ab0ecd 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -7470,7 +7470,8 @@ default_binds_local_p_3 (const_tree exp, bool shlib, bool weak_dominate,
      FIXME: We can resolve the weakref case more curefuly by looking at the
      weakref alias.  */
   if (lookup_attribute ("weakref", DECL_ATTRIBUTES (exp))
-      || (TREE_CODE (exp) == FUNCTION_DECL
+      || (!targetm.ifunc_ref_local_ok ()
+	  && TREE_CODE (exp) == FUNCTION_DECL
 	  && cgraph_node::get (exp)
 	  && cgraph_node::get (exp)->ifunc_resolver))
     return false;
-- 
2.31.1



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