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From e7fbaebc8ff650df76f43e92cb9ca59d5174ebe7 Mon Sep 17 00:00:00 2001
From: hjl <hjl@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu, 15 Mar 2018 17:54:40 +0000
Subject: [PATCH 13/13] i386: Don't generate alias for function return thunk
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.
gcc/
Backport from mainline
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/
Backport from mainline
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 | 92 ++++++++++-------------------
gcc/testsuite/gcc.target/i386/ret-thunk-9.c | 2 +-
2 files changed, 33 insertions(+), 61 deletions(-)
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 21c3c18bd3c..f4cd1c6f4e9 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -11067,19 +11067,23 @@ 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
@@ -11226,16 +11230,18 @@ output_indirect_thunk (bool need_bnd_p, unsigned int regno)
/* Output a funtion with a call and return thunk for indirect branch.
If BND_P is true, the BND prefix is needed. If REGNO != INVALID_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 (bool need_bnd_p, unsigned int regno)
+output_indirect_thunk_function (bool need_bnd_p, 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_bnd_p, false);
+ indirect_thunk_name (name, regno, need_bnd_p, ret_p);
decl = build_decl (BUILTINS_LOCATION, FUNCTION_DECL,
get_identifier (name),
build_function_type_list (void_type_node, NULL_TREE));
@@ -11278,50 +11284,6 @@ output_indirect_thunk_function (bool need_bnd_p, unsigned int regno)
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_bnd_p)
- 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_bnd_p, 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);
@@ -11368,19 +11330,29 @@ ix86_code_end (void)
rtx xops[2];
unsigned int regno;
+ if (indirect_return_needed)
+ output_indirect_thunk_function (false, INVALID_REGNUM, true);
+ if (indirect_return_bnd_needed)
+ output_indirect_thunk_function (true, INVALID_REGNUM, true);
+
+ if (indirect_return_via_cx)
+ output_indirect_thunk_function (false, CX_REG, true);
+ if (indirect_return_via_cx_bnd)
+ output_indirect_thunk_function (true, CX_REG, true);
+
if (indirect_thunk_needed)
- output_indirect_thunk_function (false, INVALID_REGNUM);
+ output_indirect_thunk_function (false, INVALID_REGNUM, false);
if (indirect_thunk_bnd_needed)
- output_indirect_thunk_function (true, INVALID_REGNUM);
+ output_indirect_thunk_function (true, 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 (false, regno);
+ output_indirect_thunk_function (false, regno, false);
if ((indirect_thunks_bnd_used & (1 << i)))
- output_indirect_thunk_function (true, regno);
+ output_indirect_thunk_function (true, regno, false);
}
for (regno = AX_REG; regno <= SP_REG; regno++)
@@ -11389,10 +11361,10 @@ ix86_code_end (void)
tree decl;
if ((indirect_thunks_used & (1 << regno)))
- output_indirect_thunk_function (false, regno);
+ output_indirect_thunk_function (false, regno, false);
if ((indirect_thunks_bnd_used & (1 << regno)))
- output_indirect_thunk_function (true, regno);
+ output_indirect_thunk_function (true, regno, false);
if (!(pic_labels_used & (1 << regno)))
continue;
@@ -28077,12 +28049,12 @@ ix86_output_function_return (bool long_p)
true);
if (need_bnd_p)
{
- 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 d2df8b874e0..eee230ca2f6 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 } } */
--
2.16.3
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