Re: [PATCH] Generate a label for the split cold function while using -freorder-blocks-and-partition

[Sriraman Tallam]

On Tue, Apr 23, 2013 at 9:59 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> On Tue, Apr 23, 2013 at 03:58:06PM -0700, Sriraman Tallam wrote:
>>   This patch generates 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.
>>
>>   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 assembler name.
>>         * gcc.dg/tree-prof/cold_partition_label.c: New test.
>
> This doesn't honor NO_DOT_IN_LABEL (and NO_DOLLAR_IN_LABEL).

Fixed, by calling clean_symbol_name

> Also, don't some function start in cold section and then switch into hot
> section?

I am not able to generate a test where this happens. However, I  fixed
this problem by generating the cold label only when the first function
block is not cold.

Patch attached, please see if this is ok.

Thanks
Sri

>
>         Jakub

Index: final.c
===================================================================
--- final.c     (revision 198212)
+++ final.c     (working copy)
@@ -2101,6 +2101,22 @@ 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 function's assembler name.  */
+         if (in_cold_section_p)
+           {
+             char *cold_function_name;
+             const char *mangled_function_name;
+             tree asm_name = DECL_ASSEMBLER_NAME (current_function_decl);
+
+             mangled_function_name = IDENTIFIER_POINTER (asm_name);
+             cold_function_name = XNEWVEC (char,
+                 strlen (mangled_function_name) + strlen (".cold") + 1);
+             sprintf (cold_function_name, "%s.cold", mangled_function_name);
+             clean_symbol_name (cold_function_name);
+             ASM_OUTPUT_LABEL (asm_out_file, cold_function_name);
+             XDELETEVEC (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 } } */