On Tue, Nov 4, 2014 at 10:46 AM, Uros Bizjak <ubiz...@gmail.com> wrote:
>> Following patch fixes PR 63538, where the data in the large data
>> section was accessed through 32bit address. The patch unifies places
>> where large data sections are determined and passes all declarations
>> to ix86_in_large_data_p only.
>>
>> The patch fixes the testcase form the PR. Also, the code from several
>> tests involving various -mlarge-data-threshold= settings looks
>> consistent now.
[...]
> We probably want to avoid putting automatic variables (and STRING_CSTs
> ?) to large data section. However, it is important that we use the
> same condition in ix86_encode_section_info and
> x86_64_elf_select_section (and likes), otherwise the data can go into
> large section, while the access to the data will be via limited 32bit
> pointers.
>
> The attached alternative patch rejects automatic variables and
> STRING_CSTs from large data sections. Please note, that it still
> access the data with the correct instructions.
Considering that STRING_CSTs always have TREE_STATIC set, the patch
should allow them, similar to the patch at [1].
Attached is the final patch.
2014-11-04 Uros Bizjak <ubiz...@gmail.com>
PR target/63538
* config/i386/i386.c (in_large_data_p): Reject automatic variables.
(ix86_encode_section_info): Do not check for non-automatic varibles
when setting SYMBOL_FLAG_FAR_ADDR flag.
(x86_64_elf_select_section): Do not check ix86_cmodel here.
(x86_64_elf_unique_section): Ditto.
(x86_elf_aligned_common): Emit tab before .largecomm.
testsuite/ChangeLog:
2014-11-03 Uros Bizjak <ubiz...@gmail.com>
PR target/63538
* gcc.target/i386/pr63538.c: New test.
I plan to commit the patch in a couple of days to mainline and 4.9 branch.
[1] https://gcc.gnu.org/ml/gcc-patches/2014-10/msg01963.html
Uros.
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c (revision 217089)
+++ gcc/config/i386/i386.c (working copy)
@@ -5066,6 +5066,10 @@ ix86_in_large_data_p (tree exp)
if (TREE_CODE (exp) == FUNCTION_DECL)
return false;
+ /* Automatic variables are never large data. */
+ if (TREE_CODE (exp) == VAR_DECL && !is_global_var (exp))
+ return false;
+
if (TREE_CODE (exp) == VAR_DECL && DECL_SECTION_NAME (exp))
{
const char *section = DECL_SECTION_NAME (exp);
@@ -5099,8 +5103,7 @@ ATTRIBUTE_UNUSED static section *
x86_64_elf_select_section (tree decl, int reloc,
unsigned HOST_WIDE_INT align)
{
- if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC)
- && ix86_in_large_data_p (decl))
+ if (ix86_in_large_data_p (decl))
{
const char *sname = NULL;
unsigned int flags = SECTION_WRITE;
@@ -5186,8 +5189,7 @@ x86_64_elf_section_type_flags (tree decl, const ch
static void ATTRIBUTE_UNUSED
x86_64_elf_unique_section (tree decl, int reloc)
{
- if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC)
- && ix86_in_large_data_p (decl))
+ if (ix86_in_large_data_p (decl))
{
const char *prefix = NULL;
/* We only need to use .gnu.linkonce if we don't have COMDAT groups. */
@@ -5256,7 +5258,7 @@ x86_elf_aligned_common (FILE *file,
{
if ((ix86_cmodel == CM_MEDIUM || ix86_cmodel == CM_MEDIUM_PIC)
&& size > (unsigned int)ix86_section_threshold)
- fputs (".largecomm\t", file);
+ fputs ("\t.largecomm\t", file);
else
fputs (COMMON_ASM_OP, file);
assemble_name (file, name);
@@ -44230,9 +44232,7 @@ ix86_encode_section_info (tree decl, rtx rtl, int
{
default_encode_section_info (decl, rtl, first);
- if (TREE_CODE (decl) == VAR_DECL
- && (TREE_STATIC (decl) || DECL_EXTERNAL (decl))
- && ix86_in_large_data_p (decl))
+ if (ix86_in_large_data_p (decl))
SYMBOL_REF_FLAGS (XEXP (rtl, 0)) |= SYMBOL_FLAG_FAR_ADDR;
}
Index: gcc/testsuite/gcc.target/i386/pr63538.c
===================================================================
--- gcc/testsuite/gcc.target/i386/pr63538.c (revision 0)
+++ gcc/testsuite/gcc.target/i386/pr63538.c (working copy)
@@ -0,0 +1,13 @@
+/* PR target/63538 */
+/* { dg-do compile } */
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O2 -mcmodel=medium -mlarge-data-threshold=0" } */
+
+static char *str = "Hello World";
+
+char *foo ()
+{
+ return str;
+}
+
+/* { dg-final { scan-assembler "movabs" } } */
