http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55953
--- Comment #3 from Evgeniy Dushistov <dushistov at mail dot ru> 2013-01-12
00:13:09 UTC ---
Cross compiling for arm, g++ have almost the same version:
arm-angstrom-linux-gnueabi-g++ (Linaro GCC 4.7-2012.10) 4.7.3 20121001:
variant one (for):
movw r3, #2280 ; 0x8e8
movt r3, #1
vmov.i8 q8, #48 ; 0x30
mov r2, #48 ; 0x30
vst1.64 {d16-d17}, [r3 :64]
vstr d16, [r3, #16]
vstr d17, [r3, #24]
vstr d16, [r3, #32]
vstr d17, [r3, #40] ; 0x28
vstr d16, [r3, #48] ; 0x30
vstr d17, [r3, #56] ; 0x38
vstr d16, [r3, #64] ; 0x40
vstr d17, [r3, #72] ; 0x48
vstr d16, [r3, #80] ; 0x50
vstr d17, [r3, #88] ; 0x58
strb r2, [r3, #96] ; 0x60
strb r2, [r3, #97] ; 0x61
strb r2, [r3, #98] ; 0x62
strb r2, [r3, #99] ; 0x63
bx lr
variant two(memset):
movw r0, #2272 ; 0x8e0
mov r1, #48 ; 0x30
movt r0, #1
mov r2, #100 ; 0x64
b 0x8494 <memset>
The time difference near 5%, the first variant win,
command line options:
-march=armv7-a -mtune=cortex-a8 -mcpu=cortex-a8 -mfpu=neon -mfloat-abi=hard
-Ofast
