Bug 41355 - Type of ADDR_EXPR in CALL_EXPR not rebuilt when function is cloned
Summary: Type of ADDR_EXPR in CALL_EXPR not rebuilt when function is cloned
Status: RESOLVED FIXED
Alias: None
Product: gcc
Classification: Unclassified
Component: tree-optimization (show other bugs)
Version: 4.5.0
: P3 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2009-09-14 16:38 UTC by baldrick@free.fr
Modified: 2010-07-07 21:24 UTC (History)
4 users (show)

See Also:
Host:
Target:
Build:
Known to work:
Known to fail:
Last reconfirmed: 2010-07-05 18:43:39


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Description baldrick@free.fr 2009-09-14 16:38:19 UTC
Testcase, compile at -O2.  A clone "g.clone.0" is formed which is the same as "g", only the second argument has been dropped.  The bug is that in the CALL_EXPR the type of the called function is still the original type.

// begin testcase
static __attribute__((noinline)) int g(int i, int j) { 
   if (j != 0) return 0;
   return i;
}
int f(int i) { return g(i, 0); }
// end testcase

Breaking on verify_gimple_call, and waiting until after "Assembling functions: g.clone.0 float" is printed, notice how the type of the addr_expr is a pointer
to "type <function_type 0x7ffff70c2540 type <integer_type 0x7ffff7e8c540 int>", while the type of g.clone.0 (see arg 0) is "type <function_type 0x7ffff70c2e40 type <integer_type 0x7ffff7e8c540 int>", and these two types do not match, though they should.

(gdb) call debug_tree(fn)
 <addr_expr 0x7ffff7ff0b00
    type <pointer_type 0x7ffff70c26c0
        type <function_type 0x7ffff70c2540 type <integer_type 0x7ffff7e8c540 int>
            QI
            size <integer_cst 0x7ffff7e7b7e0 constant 8>
            unit size <integer_cst 0x7ffff7e7b810 constant 1>
            align 8 symtab 0 alias set -1 canonical type 0x7ffff70c2540
            arg-types <tree_list 0x7ffff70da3c0 value <integer_type 0x7ffff7e8c540 int>
                chain <tree_list 0x7ffff70da390 value <integer_type 0x7ffff7e8c540 int>
                    chain <tree_list 0x7ffff7e999f0 value <void_type 0x7ffff7e9b3c0 void>>>>
            pointer_to_this <pointer_type 0x7ffff70c26c0>>
        unsigned DI
        size <integer_cst 0x7ffff7e7bb70 constant 64>
        unit size <integer_cst 0x7ffff7e7bba0 constant 8>
        align 64 symtab 0 alias set -1 canonical type 0x7ffff70c26c0>
    readonly constant
    arg 0 <function_decl 0x7ffff7123200 g.clone.0
        type <function_type 0x7ffff70c2e40 type <integer_type 0x7ffff7e8c540 int>
            QI size <integer_cst 0x7ffff7e7b7e0 8> unit size <integer_cst 0x7ffff7e7b810 1>
            align 8 symtab 0 alias set -1 canonical type 0x7ffff70c2540
            arg-types <tree_list 0x7ffff70daa20 value <integer_type 0x7ffff7e8c540 int> chain <tree_list 0x7ffff7e999f0>>
            pointer_to_this <pointer_type 0x7ffff70c26c0>>
        readonly addressable asm_written used nothrow static decl_5 QI file clone.c line 1 col 38 align 8 attributes <tree_list 0x7ffff70da3f0> initial <error_mark 0x7ffff7e86e60> abstract_origin <function_decl 0x7ffff70c1c00 g>
        arguments <parm_decl 0x7ffff7e84d80 i type <integer_type 0x7ffff7e8c540 int>
            used SI file clone.c line 1 col 44
            size <integer_cst 0x7ffff7e7ba80 constant 32>
            unit size <integer_cst 0x7ffff7e7b6f0 constant 4>
            align 32 context <function_decl 0x7ffff7123200 g.clone.0> abstract_origin <parm_decl 0x7ffff7e846c0 i>
            (reg/v:SI 0 ax [orig:59 i ] [59]) arg-type <integer_type 0x7ffff7e8c540 int>
            incoming-rtl (reg:SI 5 di [ i ])>
        result <result_decl 0x7ffff70db100 D.2707 type <integer_type 0x7ffff7e8c540 int>
            used ignored regdecl SI file clone.c line 1 col 38 size <integer_cst 0x7ffff7e7ba80 32> unit size <integer_cst 0x7ffff7e7b6f0 4>
            align 32 context <function_decl 0x7ffff7123200 g.clone.0> abstract_origin <result_decl 0x7ffff70db000 D.1606>
            (reg:SI 58 [ <retval> ])>
        (mem:QI (symbol_ref:DI ("g.clone.0") [flags 0x3] <function_decl 0x7ffff7123200 g.clone.0>) [0 S1 A8])>
    clone.c:5:16>
Comment 1 Duncan Sands 2010-07-05 18:43:39 UTC
It turns out that the problem is that when build_function_type_skip_args creates
the new type, TYPE_POINTER_TO for the new type is still pointing to the old type.
When gimple_call_set_fndecl is used to change the fndecl to one with less
arguments, an ADDR_EXPR is built.  The type of the ADDR_EXPR is obtained from the
TYPE_POINTER_TO field of the new type, and thus has type pointer-to-old-type
rather than pointer-to-new-type.  I'm testing the following patch.  The idea
here is that calling copy_node has no advantage.  In spite of the comment,
build_distinct_type_copy preserves attributes etc too, so it might as well
be used always.  [I think the comment refers to some earlier logic, since
the change introducing build_distinct_type_copy post-dates it].

Index: gcc-4.5/gcc/tree.c
===================================================================
--- gcc-4.5.orig/gcc/tree.c	2010-07-05 20:26:21.349376337 +0200
+++ gcc-4.5/gcc/tree.c	2010-07-05 20:29:11.582730610 +0200
@@ -7208,24 +7208,10 @@
 	new_reversed = void_list_node;
     }
 
-  /* Use copy_node to preserve as much as possible from original type
-     (debug info, attribute lists etc.)
-     Exception is METHOD_TYPEs must have THIS argument.
-     When we are asked to remove it, we need to build new FUNCTION_TYPE
-     instead.  */
-  if (TREE_CODE (orig_type) != METHOD_TYPE
-      || !bitmap_bit_p (args_to_skip, 0))
-    {
-      new_type = copy_node (orig_type);
-      TYPE_ARG_TYPES (new_type) = new_reversed;
-    }
-  else
-    {
-      new_type
-        = build_distinct_type_copy (build_function_type (TREE_TYPE (orig_type),
-							 new_reversed));
-      TYPE_CONTEXT (new_type) = TYPE_CONTEXT (orig_type);
-    }
+  new_type
+    = build_distinct_type_copy (build_function_type (TREE_TYPE (orig_type),
+                                                     new_reversed));
+  TYPE_CONTEXT (new_type) = TYPE_CONTEXT (orig_type);
 
   /* This is a new type, not a copy of an old type.  Need to reassociate
      variants.  We can handle everything except the main variant lazily.  */
Comment 2 Jan Hubicka 2010-07-05 19:02:11 UTC
Subject: Re:  Type of ADDR_EXPR in CALL_EXPR
	not rebuilt when function is cloned

> It turns out that the problem is that when build_function_type_skip_args
> creates
> the new type, TYPE_POINTER_TO for the new type is still pointing to the old
> type.
> When gimple_call_set_fndecl is used to change the fndecl to one with less
> arguments, an ADDR_EXPR is built.  The type of the ADDR_EXPR is obtained from
> the
> TYPE_POINTER_TO field of the new type, and thus has type pointer-to-old-type
> rather than pointer-to-new-type.  I'm testing the following patch.  The idea
> here is that calling copy_node has no advantage.  In spite of the comment,

The conditional you removed is about case where METHOD_TYPE is passed and "this" pointer
is not removed.  In this case we still want to produce METHOD_TYPE just with args
adjusted.  I think this functionality should be preserved.

Are attributes attached to decl (not type) also copied?

Honza
Comment 3 Duncan Sands 2010-07-05 19:14:29 UTC
Hi Honza, my original patch was silly, I'm trying this instead:

@@ -7216,7 +7216,7 @@
   if (TREE_CODE (orig_type) != METHOD_TYPE
       || !bitmap_bit_p (args_to_skip, 0))
     {
-      new_type = copy_node (orig_type);
+      new_type = build_distinct_type_copy (orig_type);
       TYPE_ARG_TYPES (new_type) = new_reversed;
     }
   else
Comment 4 Jan Hubicka 2010-07-05 19:18:50 UTC
Subject: Re:  Type of ADDR_EXPR in CALL_EXPR
	not rebuilt when function is cloned

> Hi Honza, my original patch was silly, I'm trying this instead:
This seems fine, thanks!  
Honza
Comment 5 Duncan Sands 2010-07-06 08:23:38 UTC
Even better, it actually works! :)
Comment 6 Duncan Sands 2010-07-07 15:25:25 UTC
Fixed in commits 161918 (mainline) and 161919 (gcc-4.5 branch).
Comment 7 Eric Botcazou 2010-07-07 21:24:46 UTC
> Fixed in commits 161918 (mainline) and 161919 (gcc-4.5 branch).

The right procedure is to copy-and-paste the ChangeLog entry in the commit log, this will automatically add a cross-reference with an URL to this audit trail.