Patch to stop GCC emitting (subreg (queued ...)) operands

[Richard Sandiford <r dot sandiford at redhat dot com>]

The mips compiler segfaults on the two test cases below.  GCC is emitting
instructions with QUEUED expressions for code like "if (v-- == 1)", where
"v" is a double-word value.

The problem seems to be that the simplify_gen_subreg patch to
operand_subword changed the way it handles QUEUED rtxes.  Before it
would return a null pointer, now it returns (subreg (queued ...)).  So
operand_subword_force now thinks that a QUEUED operand does not need to
be forced into a register.

I'm not sure where best to fix the problem.  Something somewhere has to
check for QUEUED operands, but should it be:

	1) operand_subword_force
	2) operand_subword
	3) simplify_gen_subreg
	4) something else?

In the patch below I went for 3).  It bootstraps on i686-pc-linux-gnu and
make check on mips-elf -mips1 showed no regressions.  I've included two test
cases because they exercise different callers of operand_subword_force
(do_jump_by_parts_greater_rtx and do_jump_by_parts_equality_rtx).

OK to install?

Richard


2001-07-09  Richard Sandiford  <rsandifo@redhat.com>

[gcc/]
	* simplify-rtx.c (simplify_gen_subreg): Return null for QUEUED rtxes.

[gcc/testsuite]
	* gcc.c-torture/compile/20010709-1.c,
	* gcc.c-torture/compile/20010709-2.c: New tests.

Index: simplify-rtx.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/simplify-rtx.c,v
retrieving revision 1.64
diff -c -p -d -r1.64 simplify-rtx.c
*** simplify-rtx.c	2001/07/02 15:43:38	1.64
--- simplify-rtx.c	2001/07/10 08:55:11
*************** simplify_gen_subreg (outermode, op, inne
*** 2464,2469 ****
--- 2464,2472 ----
        || byte >= GET_MODE_SIZE (innermode))
      abort ();
  
+   if (GET_CODE (op) == QUEUED)
+     return NULL_RTX;
+ 
    new = simplify_subreg (outermode, op, innermode, byte);
    if (new)
      return new;
*** /dev/null	Thu Aug 24 10:00:32 2000
--- testsuite/gcc.c-torture/compile/20010709-1.c	Mon Jul  9 19:18:53 2001
***************
*** 0 ****
--- 1,11 ----
+ typedef unsigned long long value;
+ 
+ void foo (value *v) {}
+ 
+ void test ()
+ {
+   value v;
+   foo (&v);
+   if (v-- > 0)
+     foo (&v);
+ }
*** /dev/null	Thu Aug 24 10:00:32 2000
--- testsuite/gcc.c-torture/compile/20010709-2.c	Tue Jul 10 09:52:08 2001
***************
*** 0 ****
--- 1,11 ----
+ typedef unsigned long long value;
+ 
+ void foo (value *v) {}
+ 
+ void test ()
+ {
+   value v;
+   foo (&v);
+   if (v-- == 1)
+     foo (&v);
+ }