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Re: [PATCH] Make mergeable read-only sections per-function, if requested.
- From: Segher Boessenkool <segher at kernel dot crashing dot org>
- To: Jeff Law <law at redhat dot com>
- Cc: Marek Polacek <polacek at redhat dot com>, gcc-patches at gcc dot gnu dot org
- Date: Thu, 7 May 2015 10:51:53 -0500
- Subject: Re: [PATCH] Make mergeable read-only sections per-function, if requested.
- Authentication-results: sourceware.org; auth=none
- References: <8f67f9aad3d5b98cb428dea0316a86615b89adb9 dot 1430937961 dot git dot segher at kernel dot crashing dot org> <20150507081507 dot GA3384 at redhat dot com> <20150507123058 dot GA23850 at gate dot crashing dot org> <554B6935 dot 9040300 at redhat dot com>
On Thu, May 07, 2015 at 07:31:33AM -0600, Jeff Law wrote:
> If you could cobble together a little test (ppc specific is fine with
> me) it'd be appreciated.
>
> With that, approved for the trunk.
I did one for *-*-linux*. Tested on powerpc64-linux and x86_64-linux.
Committed.
Segher
2015-05-07 Segher Boessenkool <segher@kernel.crashing.org>
gcc/
PR middle-end/192
PR middle-end/54303
* varasm.c (function_mergeable_rodata_prefix): New function.
(mergeable_string_section): Use it.
(mergeable_constant_section): Use it.
gcc/testsuite/
PR middle-end/192
PR middle-end/54303
* gcc.dg/fdata-sections-2.c: New file.
---
gcc/testsuite/gcc.dg/fdata-sections-2.c | 18 ++++++++++++++++++
gcc/varasm.c | 16 ++++++++++++++--
2 files changed, 32 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/fdata-sections-2.c
diff --git a/gcc/testsuite/gcc.dg/fdata-sections-2.c b/gcc/testsuite/gcc.dg/fdata-sections-2.c
new file mode 100644
index 0000000..dda90ba7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/fdata-sections-2.c
@@ -0,0 +1,18 @@
+/* PR middle-end/192 */
+/* PR middle-end/54303 */
+
+/* This checks that string constants are put in per-function rodata
+ sections, so that they can be garbage collected. */
+
+/* { dg-do compile { target *-*-linux* } } */
+/* { dg-options "-O -ffunction-sections -fdata-sections" } */
+
+const char *f1(void) { return "falderalde"; }
+const char *f2(void) { return "a"; }
+const char *f3(void) { return "falderalde"; }
+const char *f4(void) { return "eralde"; }
+
+/* { dg-final { scan-assembler {\.rodata\.f1\.str} } } */
+/* { dg-final { scan-assembler {\.rodata\.f2\.str} } } */
+/* { dg-final { scan-assembler-not {\.rodata\.f3\.str} } } */
+/* { dg-final { scan-assembler {\.rodata\.f4\.str} } } */
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 62d5163..11cb2c5 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -783,6 +783,18 @@ default_no_function_rodata_section (tree decl ATTRIBUTE_UNUSED)
return readonly_data_section;
}
+/* A subroutine of mergeable_string_section and mergeable_constant_section. */
+
+static const char *
+function_mergeable_rodata_prefix (void)
+{
+ section *s = targetm.asm_out.function_rodata_section (current_function_decl);
+ if (SECTION_STYLE (s) == SECTION_NAMED)
+ return s->named.name;
+ else
+ return targetm.asm_out.mergeable_rodata_prefix;
+}
+
/* Return the section to use for string merging. */
static section *
@@ -804,7 +816,7 @@ mergeable_string_section (tree decl ATTRIBUTE_UNUSED,
const char *str;
HOST_WIDE_INT i;
int j, unit;
- const char *prefix = targetm.asm_out.mergeable_rodata_prefix;
+ const char *prefix = function_mergeable_rodata_prefix ();
char *name = (char *) alloca (strlen (prefix) + 30);
mode = TYPE_MODE (TREE_TYPE (TREE_TYPE (decl)));
@@ -857,7 +869,7 @@ mergeable_constant_section (machine_mode mode ATTRIBUTE_UNUSED,
&& align <= 256
&& (align & (align - 1)) == 0)
{
- const char *prefix = targetm.asm_out.mergeable_rodata_prefix;
+ const char *prefix = function_mergeable_rodata_prefix ();
char *name = (char *) alloca (strlen (prefix) + 30);
sprintf (name, "%s.cst%d", prefix, (int) (align / 8));
--
1.8.1.4