[Bug tree-optimization/17647] [4.0 regression] Missing i386 addressing modes

[uros at kss-loka dot si]

------- Additional Comments From uros at kss-loka dot si  2004-11-05 08:00 -------
Another comment on code in comment #3:

LEA instruction uses only 32bit constant as a displacement. The code size of
inner loop is considerably bigger in gcc-4.0 compiled code. (Note that LEA with
a scale factor should be replaced by a shift in P4 case...)

Another feature would be to use an %ecx as a count register in inner loops. In
this case, TARGET_USE_LOOP architectures (such as K6) could use a loop insn for
inner loops.

gcc-4.0 (21 bytes)
  23:	8d 04 d5 00 00 00 00 	lea    0x0(,%edx,8),%eax
  2a:	dd 04 01             	fldl   (%ecx,%eax,1)
  2d:	dd 1c 03             	fstpl  (%ebx,%eax,1)
  30:	83 c2 01             	add    $0x1,%edx
  33:	39 55 0c             	cmp    %edx,0xc(%ebp)
  36:	7f eb                	jg     23 <LU_copy_matrix+0x23>

gcc-3.2 (13 bytes):
  22:	dd 04 c2             	fldl   (%edx,%eax,8)
  25:	dd 1c c1             	fstpl  (%ecx,%eax,8)
  28:	83 c0 01             	add    $0x1,%eax
  2b:	39 f0                	cmp    %esi,%eax
  2d:	7c f3                	jl     22 <LU_copy_matrix+0x22>


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17647