------- Comment #38 from sandra at codesourcery dot com 2010-07-21 16:08
-------
On reading the code again, I think the -7 is coming from the can_autoinc case
in determine_use_iv_cost_address. I also think it is correct to prefer
autoinc. E.g., here's the generated code for the loop in r161843:
.L2:
addi 11,8,9216
ldx 0,10,9
stdx 0,11,9
addi 9,9,8
bdnz .L2
and in r161844:
.L2:
ldu 0,8(11)
stdu 0,8(9)
bdnz .L2
I'm no expert on powerpc architecture, but 3 instructions versus 5 looks like a
win to me. Bit-rotten test case?
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29256
