On Tue, Nov 12, 2013 at 10:10 AM, Cary Coutant <[email protected]> wrote:
>>>> Is there a format for compiler-defined labels that would not be able
>>>> to clash with other user-generated labels?
>>>
>>> My understanding is that the "." in the generated name ensures that it
>>> will not clash with user-generated labels which cannot contain ".". So
>>> this should not be an issue.
>>
>> Is that true for all languages? I don't think we can make that
>> assumption. Also, there may be clashes with other compiler generated
>> symbols. I know of at least one Fortran compiler that composes names
>> for module symbols as "modulename.symbolname", and if symbolname is
>> "cold" then you can have a clash.
>
> GCC already uses "." to generate names for cloned functions, and picks
> a different separator for targets where "." is legal (see
> clone_function_name in cgraphclones.c). It would probably be a good
> idea to use clone_function_name to generate the new name (in
> particular, because the C++ demangler already knows how to handle that
> style when it's applied to mangled names).
I have modified my original patch to use clone_function_name to
generate the cold part label and attached it.
Thanks
Sri
>
> -cary
Patch to generate labels for cold function parts that are split when
using the option -freorder-blocks-and-partition. The cold label name
is generated by suffixing "cold" to the assembler name of the hot
function in a demangler friendly way.
This is useful when getting back traces from gdb when the cold function
part does get executed.
* final.c (final_scan_insn): Generate cold label name by suffixing
"cold" to function's name.
* gcc.dg/tree-prof/cold_partition_label.c: New test.
Index: final.c
===================================================================
--- final.c (revision 204712)
+++ final.c (working copy)
@@ -2167,6 +2167,15 @@ final_scan_insn (rtx insn, FILE *file, int optimiz
targetm.asm_out.function_switched_text_sections (asm_out_file,
current_function_decl,
in_cold_section_p);
+ /* Emit a label for the split cold section. Form label name by
+ suffixing "cold" to the original function's name. */
+ if (in_cold_section_p)
+ {
+ tree cold_function_name
+ = clone_function_name (current_function_decl, "cold");
+ ASM_OUTPUT_LABEL (asm_out_file,
+ IDENTIFIER_POINTER (cold_function_name));
+ }
break;
case NOTE_INSN_BASIC_BLOCK:
Index: testsuite/gcc.dg/tree-prof/cold_partition_label.c
===================================================================
--- testsuite/gcc.dg/tree-prof/cold_partition_label.c (revision 0)
+++ testsuite/gcc.dg/tree-prof/cold_partition_label.c (revision 0)
@@ -0,0 +1,39 @@
+/* Test case to check if function foo gets split and the cold function
+ gets a label. */
+/* { dg-require-effective-target freorder } */
+/* { dg-options "-O2 -freorder-blocks-and-partition --save-temps" } */
+
+#define SIZE 10000
+
+const char *sarr[SIZE];
+const char *buf_hot;
+const char *buf_cold;
+
+__attribute__((noinline))
+void
+foo (int path)
+{
+ int i;
+ if (path)
+ {
+ for (i = 0; i < SIZE; i++)
+ sarr[i] = buf_hot;
+ }
+ else
+ {
+ for (i = 0; i < SIZE; i++)
+ sarr[i] = buf_cold;
+ }
+}
+
+int
+main (int argc, char *argv[])
+{
+ buf_hot = "hello";
+ buf_cold = "world";
+ foo (argc);
+ return 0;
+}
+
+/* { dg-final-use { scan-assembler "foo.cold" } } */
+/* { dg-final-use { cleanup-saved-temps } } */
