[tree-ssa] work around non-canonical ptr-to-member

[Richard Henderson <rth at redhat dot com>]

On Mon, Jan 19, 2004 at 03:16:33PM -0700, law@redhat.com wrote:
> FAIL: 27_io/basic_filebuf/underflow/wchar_t/9178.cc execution test

Ugliness.  The C++ front end is creating two different ptr-to-member
structures, in this case at 

#4  0x0806c339 in build_ptrmemfunc_type (type=0x401b1ef4)
    at ../../../src-ssa/gcc/cp/decl.c:5916
#5  0x080ff4dc in build_unary_op (code=ADDR_EXPR, xarg=0x402e5e60,
    noconvert=1075519220) at ../../../src-ssa/gcc/cp/typeck.c:4058
#6  0x081007c1 in unary_complex_lvalue (code=ADDR_EXPR, arg=0x402d6a8c)
    at ../../../src-ssa/gcc/cp/typeck.c:4165
#7  0x080ff431 in build_unary_op (code=ADDR_EXPR, xarg=0x402d6a8c,
    noconvert=1126607108) at ../../../src-ssa/gcc/cp/typeck.c:3975
#8  0x080fedde in build_x_unary_op (code=ADDR_EXPR, xarg=0x402d6a8c)
    at ../../../src-ssa/gcc/cp/typeck.c:3558
#9  0x080e3fec in cp_parser_unary_expression (parser=0x4026cf00,
    address_p=false) at ../../../src-ssa/gcc/cp/parser.c:4308

and at

#4  0x0806c339 in build_ptrmemfunc_type (type=0x401af488)
    at ../../../src-ssa/gcc/cp/decl.c:5916
#5  0x0809a3c6 in tsubst (t=0x42cd128c, args=0x402e5f20, complain=tf_none,
    in_decl=0x0) at ../../../src-ssa/gcc/cp/pt.c:6877
#6  0x08099d38 in tsubst (t=0x431895c4, args=0x402e5f20, complain=tf_none,
    in_decl=0x0) at ../../../src-ssa/gcc/cp/pt.c:6557
#7  0x0809977e in tsubst_arg_types (arg_types=0x4353ea88, args=0x402e5f20,
    complain=tf_none, in_decl=0x0) at ../../../src-ssa/gcc/cp/pt.c:6371
#8  0x08099930 in tsubst_function_type (t=0x430ffd64, args=0x402e5f20,
    complain=tf_none, in_decl=0x0) at ../../../src-ssa/gcc/cp/pt.c:6433
#9  0x0809a522 in tsubst (t=0x430ffd64, args=0x402e5f20, complain=tf_none,
    in_decl=0x0) at ../../../src-ssa/gcc/cp/pt.c:6943
#10 0x080a4311 in fn_type_unification (fn=0x4310001c, explicit_targs=0x0,
    targs=0x402e5f20, args=0x402ea180, return_type=0x0, strict=116, len=-1)
    at ../../../src-ssa/gcc/cp/pt.c:8776

and then builds an assignment between the two structures.  I can work
around this for now, but it really seems to me like the C++ front end
should build a canonical ptr-to-member for any one type and remember it.


r~



	* tree-sra.c (get_scalar_for_field): Validate field.
	(create_scalar_copies): Iterate over rhs fields too.

Index: tree-sra.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/Attic/tree-sra.c,v
retrieving revision 1.1.2.16
diff -c -p -d -r1.1.2.16 tree-sra.c
*** tree-sra.c	18 Jan 2004 23:09:08 -0000	1.1.2.16
--- tree-sra.c	20 Jan 2004 17:13:22 -0000
*************** get_scalar_for_field (tree var, tree fie
*** 210,215 ****
--- 210,227 ----
  {
    struct sra_elt key;
  
+ #ifdef ENABLE_CHECKING
+   /* Validate that FIELD actually exists in VAR's type.  */
+   {
+     tree f;
+     for (f = TYPE_FIELDS (TREE_TYPE (var)); f ; f = TREE_CHAIN (f))
+       if (f == field)
+ 	goto found;
+     abort ();
+    found:;
+   }
+ #endif
+ 
    key.kind = COMPONENT_REF;
    key.base = var;
    key.field = field;
*************** create_scalar_copies (tree lhs, tree rhs
*** 686,710 ****
      }
    else
      {
!       tree f;
  
!       for (f = TYPE_FIELDS (type); f; f = TREE_CHAIN (f))
  	{
  	  tree lhs_var, rhs_var;
  
  	  /* Only copy FIELD_DECLs.  */
! 	  if (TREE_CODE (f) != FIELD_DECL)
  	    continue;
  
  	  if (mode == FIELD_SCALAR)
! 	    lhs_var = csc_build_component_ref (lhs, f);
  	  else
! 	    lhs_var = get_scalar_for_field (lhs, f);
  
  	  if (mode == SCALAR_FIELD)
! 	    rhs_var = csc_build_component_ref (rhs, f);
  	  else
! 	    rhs_var = get_scalar_for_field (rhs, f);
  
  	  csc_assign (&tsi, lhs_var, rhs_var);
  	}
--- 698,729 ----
      }
    else
      {
!       tree lf, rf;
  
!       /* ??? C++ generates copies between different pointer-to-member
! 	 structures of different types.  To combat this, we must track
! 	 the field of both the left and right structures, so that we
! 	 index the variables with fields of their own type.  */
! 
!       for (lf = TYPE_FIELDS (type), rf = TYPE_FIELDS (TREE_TYPE (rhs));
! 	   lf;
! 	   lf = TREE_CHAIN (lf), rf = TREE_CHAIN (rf))
  	{
  	  tree lhs_var, rhs_var;
  
  	  /* Only copy FIELD_DECLs.  */
! 	  if (TREE_CODE (lf) != FIELD_DECL)
  	    continue;
  
  	  if (mode == FIELD_SCALAR)
! 	    lhs_var = csc_build_component_ref (lhs, lf);
  	  else
! 	    lhs_var = get_scalar_for_field (lhs, lf);
  
  	  if (mode == SCALAR_FIELD)
! 	    rhs_var = csc_build_component_ref (rhs, rf);
  	  else
! 	    rhs_var = get_scalar_for_field (rhs, rf);
  
  	  csc_assign (&tsi, lhs_var, rhs_var);
  	}