i386: Don't generate alias for function return thunk

Message ID 20180226204843.GA232084@intel.com
State New
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Series
  • i386: Don't generate alias for function return thunk
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Commit Message

H.J. Lu Feb. 26, 2018, 8:48 p.m.
Function return thunks shouldn't be aliased to indirect branch thunks
since indirect branch thunks are placed in COMDAT section and a COMDAT
section with indirect branch may not have function return thunk.  This
patch generates function return thunks directly.

Tested on i686 and x86-64.  OK for trunk?

H.J.
---
gcc/

	PR target/84574
	* config/i386/i386.c (indirect_thunk_needed): Update comments.
	(indirect_thunk_bnd_needed): Likewise.
	(indirect_thunks_used): Likewise.
	(indirect_thunks_bnd_used): Likewise.
	(indirect_return_needed): New.
	(indirect_return_bnd_needed): Likewise.
	(output_indirect_thunk_function): Add a bool argument for
	function return.
	(output_indirect_thunk_function): Don't generate alias for
	function return thunk.
	(ix86_code_end): Call output_indirect_thunk_function to generate
	function return thunks.
	(ix86_output_function_return): Set indirect_return_bnd_needed
	and indirect_return_needed instead of indirect_thunk_bnd_needed
	and indirect_thunk_needed.

gcc/testsuite/

	PR target/84574
	* gcc.target/i386/ret-thunk-9.c: Expect __x86_return_thunk
	label instead of __x86_indirect_thunk label.
---
 gcc/config/i386/i386.c                      | 95 +++++++++++------------------
 gcc/testsuite/gcc.target/i386/ret-thunk-9.c |  2 +-
 2 files changed, 36 insertions(+), 61 deletions(-)

-- 
2.14.3

Patch

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 49f872d103f..9041485bd61 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -10799,19 +10799,23 @@  ix86_setup_frame_addresses (void)
    labels in call and return thunks.  */
 static int indirectlabelno;
 
-/* True if call and return thunk functions are needed.  */
+/* True if call thunk function is needed.  */
 static bool indirect_thunk_needed = false;
-/* True if call and return thunk functions with the BND prefix are
-   needed.  */
+/* True if call thunk function with the BND prefix is needed.  */
 static bool indirect_thunk_bnd_needed = false;
 
 /* Bit masks of integer registers, which contain branch target, used
-   by call and return thunks functions.  */
+   by call thunk functions.  */
 static int indirect_thunks_used;
 /* Bit masks of integer registers, which contain branch target, used
-   by call and return thunks functions with the BND prefix.  */
+   by call thunk functions with the BND prefix.  */
 static int indirect_thunks_bnd_used;
 
+/* True if return thunk function is needed.  */
+static bool indirect_return_needed = false;
+/* True if return thunk function with the BND prefix is needed.  */
+static bool indirect_return_bnd_needed = false;
+
 /* True if return thunk function via CX is needed.  */
 static bool indirect_return_via_cx;
 /* True if return thunk function via CX with the BND prefix is
@@ -11007,17 +11011,18 @@  output_indirect_thunk (enum indirect_thunk_prefix need_prefix,
 /* Output a funtion with a call and return thunk for indirect branch.
    If BND_P is true, the BND prefix is needed.  If REGNO != UNVALID_REGNUM,
    the function address is in REGNO.  Otherwise, the function address is
-   on the top of stack.  */
+   on the top of stack.  Thunk is used for function return if RET_P is
+   true.  */
 
 static void
 output_indirect_thunk_function (enum indirect_thunk_prefix need_prefix,
-				unsigned int regno)
+				unsigned int regno, bool ret_p)
 {
   char name[32];
   tree decl;
 
   /* Create __x86_indirect_thunk/__x86_indirect_thunk_bnd.  */
-  indirect_thunk_name (name, regno, need_prefix, false);
+  indirect_thunk_name (name, regno, need_prefix, ret_p);
   decl = build_decl (BUILTINS_LOCATION, FUNCTION_DECL,
 		     get_identifier (name),
 		     build_function_type_list (void_type_node, NULL_TREE));
@@ -11060,50 +11065,6 @@  output_indirect_thunk_function (enum indirect_thunk_prefix need_prefix,
 	ASM_OUTPUT_LABEL (asm_out_file, name);
       }
 
-  /* Create alias for __x86_return_thunk/__x86_return_thunk_bnd or
-     __x86_return_thunk_ecx/__x86_return_thunk_ecx_bnd.  */
-  bool need_alias;
-  if (regno == INVALID_REGNUM)
-    need_alias = true;
-  else if (regno == CX_REG)
-    {
-      if (need_prefix == indirect_thunk_prefix_bnd)
-	need_alias = indirect_return_via_cx_bnd;
-      else
-	need_alias = indirect_return_via_cx;
-    }
-  else
-    need_alias = false;
-
-  if (need_alias)
-    {
-      char alias[32];
-
-      indirect_thunk_name (alias, regno, need_prefix, true);
-#if TARGET_MACHO
-      if (TARGET_MACHO)
-	{
-	  fputs ("\t.weak_definition\t", asm_out_file);
-	  assemble_name (asm_out_file, alias);
-	  fputs ("\n\t.private_extern\t", asm_out_file);
-	  assemble_name (asm_out_file, alias);
-	  putc ('\n', asm_out_file);
-	  ASM_OUTPUT_LABEL (asm_out_file, alias);
-	}
-#else
-      ASM_OUTPUT_DEF (asm_out_file, alias, name);
-      if (USE_HIDDEN_LINKONCE)
-	{
-	  fputs ("\t.globl\t", asm_out_file);
-	  assemble_name (asm_out_file, alias);
-	  putc ('\n', asm_out_file);
-	  fputs ("\t.hidden\t", asm_out_file);
-	  assemble_name (asm_out_file, alias);
-	  putc ('\n', asm_out_file);
-	}
-#endif
-    }
-
   DECL_INITIAL (decl) = make_node (BLOCK);
   current_function_decl = decl;
   allocate_struct_function (decl, false);
@@ -11150,23 +11111,37 @@  ix86_code_end (void)
   rtx xops[2];
   unsigned int regno;
 
+  if (indirect_return_needed)
+    output_indirect_thunk_function (indirect_thunk_prefix_none,
+				    INVALID_REGNUM, true);
+  if (indirect_return_bnd_needed)
+    output_indirect_thunk_function (indirect_thunk_prefix_bnd,
+				    INVALID_REGNUM, true);
+
+  if (indirect_return_via_cx)
+    output_indirect_thunk_function (indirect_thunk_prefix_none,
+				    CX_REG, true);
+  if (indirect_return_via_cx_bnd)
+    output_indirect_thunk_function (indirect_thunk_prefix_bnd,
+				    CX_REG, true);
+
   if (indirect_thunk_needed)
     output_indirect_thunk_function (indirect_thunk_prefix_none,
-				    INVALID_REGNUM);
+				    INVALID_REGNUM, false);
   if (indirect_thunk_bnd_needed)
     output_indirect_thunk_function (indirect_thunk_prefix_bnd,
-				    INVALID_REGNUM);
+				    INVALID_REGNUM, false);
 
   for (regno = FIRST_REX_INT_REG; regno <= LAST_REX_INT_REG; regno++)
     {
       unsigned int i = regno - FIRST_REX_INT_REG + LAST_INT_REG + 1;
       if ((indirect_thunks_used & (1 << i)))
 	output_indirect_thunk_function (indirect_thunk_prefix_none,
-					regno);
+					regno, false);
 
       if ((indirect_thunks_bnd_used & (1 << i)))
 	output_indirect_thunk_function (indirect_thunk_prefix_bnd,
-					regno);
+					regno, false);
     }
 
   for (regno = FIRST_INT_REG; regno <= LAST_INT_REG; regno++)
@@ -11176,11 +11151,11 @@  ix86_code_end (void)
 
       if ((indirect_thunks_used & (1 << regno)))
 	output_indirect_thunk_function (indirect_thunk_prefix_none,
-					regno);
+					regno, false);
 
       if ((indirect_thunks_bnd_used & (1 << regno)))
 	output_indirect_thunk_function (indirect_thunk_prefix_bnd,
-					regno);
+					regno, false);
 
       if (!(pic_labels_used & (1 << regno)))
 	continue;
@@ -29039,12 +29014,12 @@  ix86_output_function_return (bool long_p)
 			       true);
 	  if (need_prefix == indirect_thunk_prefix_bnd)
 	    {
-	      indirect_thunk_bnd_needed |= need_thunk;
+	      indirect_return_bnd_needed |= need_thunk;
 	      fprintf (asm_out_file, "\tbnd jmp\t%s\n", thunk_name);
 	    }
 	  else
 	    {
-	      indirect_thunk_needed |= need_thunk;
+	      indirect_return_needed |= need_thunk;
 	      fprintf (asm_out_file, "\tjmp\t%s\n", thunk_name);
 	    }
 	}
diff --git a/gcc/testsuite/gcc.target/i386/ret-thunk-9.c b/gcc/testsuite/gcc.target/i386/ret-thunk-9.c
index b75fc9219b0..819671af933 100644
--- a/gcc/testsuite/gcc.target/i386/ret-thunk-9.c
+++ b/gcc/testsuite/gcc.target/i386/ret-thunk-9.c
@@ -13,7 +13,7 @@  foo (void)
 /* { dg-final { scan-assembler "jmp\[ \t\]*__x86_return_thunk" } } */
 /* { dg-final { scan-assembler "jmp\[ \t\]*\.LIND" } } */
 /* { dg-final { scan-assembler "call\[ \t\]*\.LIND" } } */
-/* { dg-final { scan-assembler "__x86_indirect_thunk:" } } */
+/* { dg-final { scan-assembler "__x86_return_thunk:" } } */
 /* { dg-final { scan-assembler "mov(?:l|q)\[ \t\]*_?bar" { target *-*-linux* } } } */
 /* { dg-final { scan-assembler-times {\tpause} 2 } } */
 /* { dg-final { scan-assembler-times {\tlfence} 2 } } */