PATCH: PR optimization/9016

[Mark Mitchell]

Here's a patch for PR9016, a failure to optimize floating-point
computations appropriately when inlining.

The problem is that we commit to code-shape too early; we generate:

  (SET (MEM (ADDRESSOF (REG))) (CONST_DOUBLE ...))

and then cannot simplify this to:

  (SET (REG) (CONST_DOUBLE ...))

so we end up dumping the constant to memory.

If we think we are setting a REG in the first place, we do:

  (SET (REG) (MEM (SYMBOL_REF (.LCXX))))

which we then do a better job simplifying.

This test makes us always load CONST_DOUBLEs from the constant pool,
which gives the optimal code for the test case in the PR.

I'll check in this patch shortly, if nobody tells me it's a horrible
mistake.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com


2003-03-14  Mark Mitchell  <mark@codesourcery.com>

	PR optimization/9016
	* config/i386/i386.c (ix86_expand_move): Force more CONST_DOUBLEs
	into the constant pool.

Index: config/i386/i386.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/i386/i386.c,v
retrieving revision 1.548
diff -c -5 -p -r1.548 i386.c
*** config/i386/i386.c	12 Mar 2003 18:06:29 -0000	1.548
--- config/i386/i386.c	14 Mar 2003 07:07:00 -0000
*************** ix86_expand_move (mode, operands)
*** 8371,8383 ****
  	     force the value to memory now, since we'll get better code
  	     out the back end.  */
  
  	  if (strict)
  	    ;
! 	  else if (GET_CODE (op1) == CONST_DOUBLE
! 		   && register_operand (op0, mode))
! 	    op1 = validize_mem (force_const_mem (mode, op1));
  	}
      }
  
    insn = gen_rtx_SET (VOIDmode, op0, op1);
  
--- 8371,8391 ----
  	     force the value to memory now, since we'll get better code
  	     out the back end.  */
  
  	  if (strict)
  	    ;
! 	  else if (GET_CODE (op1) == CONST_DOUBLE)
! 	    {
! 	      op1 = validize_mem (force_const_mem (mode, op1));
! 	      if (!register_operand (op0, mode))
! 		{
! 		  rtx temp = gen_reg_rtx (mode);
! 		  emit_insn (gen_rtx_SET (VOIDmode, temp, op1));
! 		  emit_move_insn (op0, temp);
! 		  return;
! 		}
! 	    }
  	}
      }
  
    insn = gen_rtx_SET (VOIDmode, op0, op1);