Re: don't output strings just because of debug information

[Alexandre Oliva <aoliva at redhat dot com>]

On Dec  9, 2007, Mark Mitchell <mark@codesourcery.com> wrote:

> Ian Lance Taylor wrote:
>> Alexandre Oliva <aoliva@redhat.com> writes:
>> 
>>> From  Alexandre Oliva  <aoliva@redhat.com>
>>> 
>>> * dwarf2out.c (reference_to_unused): Don't emit strings in
>>> initializers just because of debug information.
>> 
>> This is OK.

> I think it's OK too, but I have a couple of follow-on requests. :-)

> 1. tree.h doesn't document TREE_ASM_WRITTEN as applying to STRING_CST.
> I didn't know that we set it on STRING_CST, so I was initially surprised
> by Alexandre's patch.  Alexandre, would you mind updating that?

> 2. Is it possible to write a test case?

Thanks, here's what I've just checked in:

for  gcc/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* dwarf2out.c (reference_to_unused): Don't emit strings in
	initializers just because of debug information.
	* tree.h (TREE_ASM_WRITTEN): Document use for STRING_CSTs.

for  gcc/testsuite/ChangeLog
from  Alexandre Oliva  <aoliva@redhat.com>

	* gcc.dg/debug/const-3.c: New.

Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c.orig	2007-12-14 04:11:00.000000000 -0200
+++ gcc/dwarf2out.c	2007-12-14 04:13:03.000000000 -0200
@@ -10365,6 +10365,8 @@ reference_to_unused (tree * tp, int * wa
       if (!node->output)
 	return *tp;
     }
+  else if (TREE_CODE (*tp) == STRING_CST && !TREE_ASM_WRITTEN (*tp))
+    return *tp;
 
   return NULL_TREE;
 }
Index: gcc/tree.h
===================================================================
--- gcc/tree.h.orig	2007-12-14 04:11:00.000000000 -0200
+++ gcc/tree.h	2007-12-14 04:14:08.000000000 -0200
@@ -546,7 +546,7 @@ struct gimple_stmt GTY(())
 
        TREE_ASM_WRITTEN in
            VAR_DECL, FUNCTION_DECL, RECORD_TYPE, UNION_TYPE, QUAL_UNION_TYPE
-	   BLOCK, SSA_NAME
+	   BLOCK, SSA_NAME, STRING_CST
 
    used_flag:
 
@@ -1300,7 +1300,7 @@ extern void omp_clause_range_check_faile
 /* In integral and pointer types, means an unsigned type.  */
 #define TYPE_UNSIGNED(NODE) (TYPE_CHECK (NODE)->base.unsigned_flag)
 
-/* Nonzero in a VAR_DECL means assembler code has been written.
+/* Nonzero in a VAR_DECL or STRING_CST means assembler code has been written.
    Nonzero in a FUNCTION_DECL means that the function has been compiled.
    This is interesting in an inline function, since it might not need
    to be compiled separately.
Index: gcc/testsuite/gcc.dg/debug/const-3.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ gcc/testsuite/gcc.dg/debug/const-3.c	2007-12-14 04:23:45.000000000 -0200
@@ -0,0 +1,7 @@
+/* Make sure we don't emit strings just because of debug information
+   for string initializers.  */
+/* { dg-do compile } */
+/* { dg-options "-O2 -g" } */
+/* { dg-final { scan-assembler-not "dontgenerate" } } */
+static const char *p = "dontgenerate1";
+static const char *q[2] = { 0, "dontgenerate2" };

-- 
Alexandre Oliva         http://www.lsd.ic.unicamp.br/~oliva/
FSF Latin America Board Member         http://www.fsfla.org/
Red Hat Compiler Engineer   aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist  oliva@{lsd.ic.unicamp.br, gnu.org}