Hi,
The PR is logged against Darwin, and (as Jakub points out in the PR thread)
indeed Darwin is missing a nonlocal_goto_receiver to restore the PIC reg in
code that uses it (most of the patch).
However, there is a second issue, and (if I've understood things correctly)
this affects GOT targets too - thus there is a single non-darwin-specific hunk
for which I need approval for X86 as a whole.
consider (x86 -fPIC -m32)
==
int g42 = 42;
int foo (void) <=== doesn't use EBX, so doesn't save it.
{
__label__ x;
int z;
int bar (int *zz) <== does use EBX, and saves it
{
*zz = g42;
goto x; <== however, EBX is not restored here.
}
bar(&z);
x:
return z;
}
==
... this all works OK when the caller of foo and foo are in one object (and
thus share the same GOT)
.. however, suppose we build the code above as a shared lib and call it from a
pie executable (or another so).
Now, when the caller (with a different GOT value from the lib) calls foo() -
EBX gets trashed (probably *boom*).
The solution proposed here (for this aspect) is that, if a function contains a
nonlocal label, then the PICbase register should be preserved. This is the
only non-darwin-specific hunk in the patch.
[For the Darwin case, it is always necessary to preserve and restore the PIC
base, since a different base is used in each function].
The remainder of the patch is darwin-specific, to provide restoration of the
pic register at non-local-goto-recievers.
==
I have verified that the patch works as expected on x86_64-linux (@m32),
i686-darwin9 and x86_64-darwin12 (@m32) - and that, otherwise, there are no
test changes (Ada and Java tested on Darwin, but not on Linux).
(Other Darwin folks {thanks!} have tested this across a wider range of Darwin
versions)
==
OK for trunk?
OK open branches? (since this is a wrong code bug)
thanks,
Iain
gcc/
PR target/51784
* config/i386/i386.c (output_set_got, DARWIN): Adjust to emit a second
label for nonlocal
goto receivers. Don't output pic base labels unless we're producing
PIC; mark that action
unreachable().
(ix86_save_reg): If the function contains a nonlocal label, save the
PIC base reg.
* config/darwin-protos.h (machopic_should_output_picbase_label): New.
* gcc/config/darwin.c (emitted_pic_label_num): New GTY.
(update_pic_label_number_if_needed): New.
(machopic_output_function_base_name): Adjust for nonlocal receiver case.
(machopic_should_output_picbase_label): New.
* config/i386/i386.md (enum unspecv): UNSPECV_NLGR: New.
(nonlocal_goto_receiver): New insn and split.
gcc/config/darwin-protos.h | 1 +
gcc/config/darwin.c | 30 +++++++++++++++++++++++++-----
gcc/config/i386/i386.c | 23 ++++++++++++++---------
gcc/config/i386/i386.md | 34 +++++++++++++++++++++++++++++++++-
4 files changed, 73 insertions(+), 15 deletions(-)
diff --git a/gcc/config/darwin-protos.h b/gcc/config/darwin-protos.h
index 0755e94..70b7fb0 100644
--- a/gcc/config/darwin-protos.h
+++ b/gcc/config/darwin-protos.h
@@ -25,6 +25,7 @@ extern void machopic_validate_stub_or_non_lazy_ptr (const
char *);
extern void machopic_output_function_base_name (FILE *);
extern const char *machopic_indirection_name (rtx, bool);
extern const char *machopic_mcount_stub_name (void);
+extern bool machopic_should_output_picbase_label (void);
#ifdef RTX_CODE
diff --git a/gcc/config/darwin.c b/gcc/config/darwin.c
index a049a5d..7e63fdf 100644
--- a/gcc/config/darwin.c
+++ b/gcc/config/darwin.c
@@ -369,14 +369,13 @@ machopic_gen_offset (rtx orig)
static GTY(()) const char * function_base_func_name;
static GTY(()) int current_pic_label_num;
+static GTY(()) int emitted_pic_label_num;
-void
-machopic_output_function_base_name (FILE *file)
+static void
+update_pic_label_number_if_needed (void)
{
const char *current_name;
- /* If dynamic-no-pic is on, we should not get here. */
- gcc_assert (!MACHO_DYNAMIC_NO_PIC_P);
/* When we are generating _get_pc thunks within stubs, there is no current
function. */
if (current_function_decl)
@@ -394,7 +393,28 @@ machopic_output_function_base_name (FILE *file)
++current_pic_label_num;
function_base_func_name = "L_machopic_stub_dummy";
}
- fprintf (file, "L%011d$pb", current_pic_label_num);
+}
+
+void
+machopic_output_function_base_name (FILE *file)
+{
+ /* If dynamic-no-pic is on, we should not get here. */
+ gcc_assert (!MACHO_DYNAMIC_NO_PIC_P);
+
+ update_pic_label_number_if_needed ();
+ fprintf (file, "L%d$pb", current_pic_label_num);
+}
+
+bool
+machopic_should_output_picbase_label (void)
+{
+ update_pic_label_number_if_needed ();
+
+ if (current_pic_label_num == emitted_pic_label_num)
+ return false;
+
+ emitted_pic_label_num = current_pic_label_num;
+ return true;
}
/* The suffix attached to non-lazy pointer symbols. */
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 5df6ab7..f523c2a 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -8827,10 +8827,8 @@ output_set_got (rtx dest, rtx label ATTRIBUTE_UNUSED)
output_asm_insn ("mov%z0\t{%2, %0|%0, %2}", xops);
#if TARGET_MACHO
- /* Output the Mach-O "canonical" label name ("Lxx$pb") here too. This
- is what will be referenced by the Mach-O PIC subsystem. */
- if (!label)
- ASM_OUTPUT_LABEL (asm_out_file, MACHOPIC_FUNCTION_BASE_NAME);
+ /* We don't need a pic base, we're not producing pic. */
+ gcc_unreachable ();
#endif
targetm.asm_out.internal_label (asm_out_file, "L",
@@ -8845,12 +8843,18 @@ output_set_got (rtx dest, rtx label ATTRIBUTE_UNUSED)
xops[2] = gen_rtx_SYMBOL_REF (Pmode, ggc_strdup (name));
xops[2] = gen_rtx_MEM (QImode, xops[2]);
output_asm_insn ("call\t%X2", xops);
- /* Output the Mach-O "canonical" label name ("Lxx$pb") here too. This
- is what will be referenced by the Mach-O PIC subsystem. */
+
#if TARGET_MACHO
- if (!label)
+ /* Output the Mach-O "canonical" pic base label name ("Lxx$pb") here.
+ This is what will be referenced by the Mach-O PIC subsystem. */
+ if (machopic_should_output_picbase_label () || !label)
ASM_OUTPUT_LABEL (asm_out_file, MACHOPIC_FUNCTION_BASE_NAME);
- else
+
+ /* When we are restoring the pic base at the site of a nonlocal label,
+ and we decided to emit the pic base above, we will still output a
+ local label used for calculating the correction offset (even though
+ the offset will be 0 in that case). */
+ if (label)
targetm.asm_out.internal_label (asm_out_file, "L",
CODE_LABEL_NUMBER (label));
#endif
@@ -8932,7 +8936,8 @@ ix86_save_reg (unsigned int regno, bool maybe_eh_return)
&& (df_regs_ever_live_p (REAL_PIC_OFFSET_TABLE_REGNUM)
|| crtl->profile
|| crtl->calls_eh_return
- || crtl->uses_const_pool))
+ || crtl->uses_const_pool
+ || cfun->has_nonlocal_label))
return ix86_select_alt_pic_regnum () == INVALID_REGNUM;
if (crtl->calls_eh_return && maybe_eh_return)
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 2777e9c..df9faf2 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -222,6 +222,8 @@
UNSPECV_XEND
UNSPECV_XABORT
UNSPECV_XTEST
+
+ UNSPECV_NLGR
])
;; Constants to represent rounding modes in the ROUND instruction
@@ -16227,7 +16229,37 @@
emit_insn (gen_set_got (pic_offset_table_rtx));
DONE;
})
-
+
+(define_insn_and_split "nonlocal_goto_receiver"
+ [(unspec_volatile [(const_int 0)] UNSPECV_NLGR)]
+ "TARGET_MACHO && !TARGET_64BIT && flag_pic"
+{
+ if (crtl->uses_pic_offset_table)
+ return "#";
+ else
+ return "# not used"; /* just for debug. */
+}
+ ""
+ [(const_int 0)]
+{
+ if (crtl->uses_pic_offset_table)
+ {
+ rtx xops[3];
+ rtx label_rtx = gen_label_rtx ();
+ rtx tmp;
+
+ /* Get a new pic base. */
+ emit_insn (gen_set_got_labelled (pic_offset_table_rtx, label_rtx));
+ /* Correct this with the offset from the new to the old. */
+ xops[0] = xops[1] = pic_offset_table_rtx;
+ label_rtx = gen_rtx_LABEL_REF (SImode, label_rtx);
+ tmp = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, label_rtx),
UNSPEC_MACHOPIC_OFFSET);
+ xops[2] = gen_rtx_CONST (Pmode, tmp);
+ ix86_expand_binary_operator (MINUS, SImode, xops);
+ }
+ DONE;
+})
+
;; Avoid redundant prefixes by splitting HImode arithmetic to SImode.
(define_split
