[PATCH]: PR 20203: unrecognizable insn building binutils

[Alan Modra <amodra at bigpond dot net dot au>]

The testcase in PR 20203 sees expand generating a memory address of the
form (plus (mem) (const_int)) which is obviously invalid on ppc.  The
cause is the expand_expr call in get_memory_rtx, which uses EXPAND_SUM.
When fed with

 <plus_expr 0x8000205798
    type <pointer_type 0x800029b9c0
        type <integer_type 0x80002074e0 unsigned char public unsigned QI
            size <integer_cst 0x80001ff4b0 constant invariant 8>
            unit size <integer_cst 0x80001ff4e0 constant invariant 1>
            align 8 symtab 0 alias set -1 precision 8 min <integer_cst 0x80001ff5a0 0> max <integer_cst 0x80001ff5d0 255>
            pointer_to_this <pointer_type 0x800029b9c0>>
        unsigned SI
        size <integer_cst 0x80001ff8a0 constant invariant 32>
        unit size <integer_cst 0x80001ff3c0 constant invariant 4>
        align 32 symtab 0 alias set -1>
   
    arg 0 <component_ref 0x800020c140 type <pointer_type 0x800029b9c0>
       
        arg 0 <indirect_ref 0x80002dd100 type <record_type 0x80002d59c0 bfd_section>
            arg 0 <parm_decl 0x80002db000 s>>
        arg 1 <field_decl 0x80002d5c30 contents type <pointer_type 0x800029b9c0>
            unsigned SI file /src/tmp/mips_miscompile.i line 6 size <integer_cst 0x80001ff8a0 32> unit size <integer_cst 0x80001ff3c0 4>
            align 32 offset_align 128
            offset <integer_cst 0x80001ff3f0 constant invariant 0> bit offset <integer_cst 0x80001ff8a0 32> context <record_type 0x80002d59c0 bfd_section> arguments <integer_cst 0x80001ff3f0 0>>>
    arg 1 <convert_expr 0x80002dd1c0 type <pointer_type 0x800029b9c0>
       
        arg 0 <convert_expr 0x80002dd140 type <integer_type 0x80002078f0 unsigned int>
           
            arg 0 <nop_expr 0x80002dd0c0 type <integer_type 0x8000207b60 long long int>
               
                arg 0 <minus_expr 0x80002056c0 type <integer_type 0x8000207a90 long unsigned int>
                   
                    arg 0 <component_ref 0x800020c0f0 type <integer_type 0x8000207a90 long unsigned int>
                       
                        arg 0 <indirect_ref 0x80002dd040 type <record_type 0x80002d59c0 bfd_section>
                            arg 0 <parm_decl 0x80002db000 s>> arg 1 <field_decl 0x80002d5b60 size>>
                    arg 1 <integer_cst 0x80002dc180 constant invariant 16>>>>>>

the chain of convert_exprs and nop_expr result in the minus_expr being
emitted, and, since this expansion is done with EXPAND_SUM it goes via
simplify_gen_binary here:

      /* Convert A - const to A + (-const).  */
      if (GET_CODE (op1) == CONST_INT)
	{
	  op1 = negate_rtx (mode, op1);
	  return REDUCE_BIT_FIELD (simplify_gen_binary (PLUS, mode, op0, op1));
	}

This particular path doesn't do anything special regarding the MEM, so
we emit invalid rtl.  I'm not sure whether expand_expr has already gone
wrong at this point, ie. whether EXPAND_SUM should mean that no
instructions are emitted on this tree, but I guess not.  The description
of EXPAND_SUM seems to preclude conversions.  (If we were left with one
big rtl expression, then break_out_memory_refs called in memory_address
would put all the mems in pseudos.)

I suppose another possibility is that this tree shouldn't be generated
in the first place..

	PR target/20203
	* builtins.c (get_memory_rtx): Expand address exp using EXPAND_NORMAL.
	Remove convert_memory_address call duplicating that in memory_address.

Bootstrap and regression tests powerpc-linux and powerpc64-linux in
progress.


Index: gcc/builtins.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/builtins.c,v
retrieving revision 1.426
diff -u -p -r1.426 builtins.c
--- gcc/builtins.c	24 Feb 2005 20:00:04 -0000	1.426
+++ gcc/builtins.c	25 Feb 2005 08:04:09 -0000
@@ -978,12 +978,8 @@ expand_builtin_prefetch (tree arglist)
 static rtx
 get_memory_rtx (tree exp)
 {
-  rtx addr = expand_expr (exp, NULL_RTX, ptr_mode, EXPAND_SUM);
-  rtx mem;
-
-  addr = convert_memory_address (Pmode, addr);
-
-  mem = gen_rtx_MEM (BLKmode, memory_address (BLKmode, addr));
+  rtx addr = expand_expr (exp, NULL_RTX, ptr_mode, EXPAND_NORMAL);
+  rtx mem = gen_rtx_MEM (BLKmode, memory_address (BLKmode, addr));
 
   /* Get an expression we can use to find the attributes to assign to MEM.
      If it is an ADDR_EXPR, use the operand.  Otherwise, dereference it if

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre