[PATCH] x86: Skip ENDBR when emitting direct call/jmp to local function

H.J. Lu hjl.tools@gmail.com
Wed Feb 23 22:35:05 GMT 2022


Skip the 4-byte ENDBR when emitting a direct call/jmp to a local function
with ENDBR at function entry.

This has been tested on Linux kernel.

gcc/

	PR target/102953
	* config/i386/i386-features.cc
	(rest_of_insert_endbr_and_patchable_area): Set
	SYMBOL_FLAG_FUNCTION_ENDBR when inserting ENDBR.
	* config/i386/i386.cc (ix86_print_operand): Skip the 4-byte ENDBR
	when calling the local function with ENDBR at function entry.
	* config/i386/i386.h (SYMBOL_FLAG_FUNCTION_ENDBR): New.
	(SYMBOL_FLAG_FUNCTION_ENDBR_P): Likewise.

gcc/testsuite/

	PR target/102953
	* gcc.target/i386/pr102953-1.c: New test.
	* gcc.target/i386/pr102953-2.c: Likewise.
---
 gcc/config/i386/i386-features.cc           |  2 ++
 gcc/config/i386/i386.cc                    | 11 +++++++-
 gcc/config/i386/i386.h                     |  5 ++++
 gcc/testsuite/gcc.target/i386/pr102953-1.c | 25 ++++++++++++++++++
 gcc/testsuite/gcc.target/i386/pr102953-2.c | 30 ++++++++++++++++++++++
 5 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/pr102953-1.c
 create mode 100644 gcc/testsuite/gcc.target/i386/pr102953-2.c

diff --git a/gcc/config/i386/i386-features.cc b/gcc/config/i386/i386-features.cc
index 6fe41c3c24f..3ca1131ed59 100644
--- a/gcc/config/i386/i386-features.cc
+++ b/gcc/config/i386/i386-features.cc
@@ -1979,6 +1979,8 @@ rest_of_insert_endbr_and_patchable_area (bool need_endbr,
 	      || (TARGET_DLLIMPORT_DECL_ATTRIBUTES
 		  && DECL_DLLIMPORT_P (cfun->decl))))
 	{
+	  rtx symbol = XEXP (DECL_RTL (cfun->decl), 0);
+	  SYMBOL_REF_FLAGS (symbol) |= SYMBOL_FLAG_FUNCTION_ENDBR;
 	  if (crtl->profile && flag_fentry)
 	    {
 	      /* Queue ENDBR insertion to x86_function_profiler.
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index b2bf90576d5..33777f942f2 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -13810,7 +13810,16 @@ ix86_print_operand (FILE *file, rtx x, int code)
       else if (flag_pic || MACHOPIC_INDIRECT)
 	output_pic_addr_const (file, x, code);
       else
-	output_addr_const (file, x);
+	{
+	  /* Skip ENDBR when emitting a direct call/jmp to a local
+	     function with ENDBR at function entry.  */
+	  if (code == 'P'
+	      && GET_CODE (x) == SYMBOL_REF
+	      && SYMBOL_REF_LOCAL_P (x)
+	      && SYMBOL_FLAG_FUNCTION_ENDBR_P (x))
+	    x = gen_rtx_PLUS (Pmode, x, GEN_INT (4));
+	  output_addr_const (file, x);
+	}
     }
 }
 
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index f41e0908250..e3e50e1ebbb 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -2786,6 +2786,11 @@ extern GTY(()) tree ms_va_list_type_node;
 #define SYMBOL_REF_STUBVAR_P(X) \
 	((SYMBOL_REF_FLAGS (X) & SYMBOL_FLAG_STUBVAR) != 0)
 
+/* Flag to mark a function with ENDBR at entry.  */
+#define SYMBOL_FLAG_FUNCTION_ENDBR	(SYMBOL_FLAG_MACH_DEP << 5)
+#define SYMBOL_FLAG_FUNCTION_ENDBR_P(X) \
+	((SYMBOL_REF_FLAGS (X) & SYMBOL_FLAG_FUNCTION_ENDBR) != 0)
+
 extern void debug_ready_dispatch (void);
 extern void debug_dispatch_window (int);
 
diff --git a/gcc/testsuite/gcc.target/i386/pr102953-1.c b/gcc/testsuite/gcc.target/i386/pr102953-1.c
new file mode 100644
index 00000000000..2afad391baf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr102953-1.c
@@ -0,0 +1,25 @@
+/* { dg-do compile { target { ! *-*-darwin* } } } */
+/* { dg-options "-O2 -fno-pic -fplt -fcf-protection" } */
+
+extern int func (int);
+
+extern int i;
+
+__attribute__ ((noclone, noinline, noipa))
+static int
+bar (int x)
+{
+  if (x == 0)
+    return x;
+  return bar (x - 1) + func (x);
+}
+
+void *
+foo (void)
+{
+  i = bar (2);
+  return bar;
+}
+
+/* { dg-final { scan-assembler-times {call\t_?bar\+4\M} 2 } } */
+/* { dg-final { scan-assembler-times {call\t_?func\M} 1 } } */
diff --git a/gcc/testsuite/gcc.target/i386/pr102953-2.c b/gcc/testsuite/gcc.target/i386/pr102953-2.c
new file mode 100644
index 00000000000..5b8d517f4f2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr102953-2.c
@@ -0,0 +1,30 @@
+/* { dg-do compile { target { ! *-*-darwin* } } } */
+/* { dg-options "-O2 -fno-pic -fplt -fcf-protection" } */
+
+static int bar (int x);
+extern int func (int);
+
+int
+foo (int i)
+{
+  return bar (i);
+}
+
+void *
+bar_p (void)
+{
+  return bar;
+}
+
+__attribute__ ((noclone, noinline, noipa))
+static int
+bar (int x)
+{
+  if (x == 0)
+    return x;
+  return bar (x - 1) + func (x);
+}
+
+/* { dg-final { scan-assembler-times {call\t_?bar\+4\M} 1 } } */
+/* { dg-final { scan-assembler-times {jmp\t_?bar\+4\M} 1 } } */
+/* { dg-final { scan-assembler-times {call\t_?func\M} 1 } } */
-- 
2.35.1



More information about the Gcc-patches mailing list