http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57540
--- Comment #1 from bin.cheng <amker.cheng at gmail dot com> ---
The dump of loop_init is like,
72: r178:SI=0
106: L106:
90: NOTE_INSN_BASIC_BLOCK 6
91: r178:SI=r178:SI+0x1
94: r190:SI=r177:SI<<0x2
REG_DEAD r177:SI
95: r191:SI=sfp:SI+r190:SI
REG_DEAD r190:SI
96: r192:SI=r191:SI-0x810
REG_DEAD r191:SI
REG_DEAD r189:SI
97: r177:SI=[r192:SI]
REG_DEAD r192:SI
98: cc:CC=cmp(r177:SI,0)
99: pc={(cc:CC>=0)?L104:pc}
REG_DEAD cc:CC
REG_BR_PROB 0x238c
Instructions 95/96 should be re-factored as below:
95: r191:SI=sfp:SI-0x810
REG_DEAD r190:SI
96: r192:SI=r191:SI+r190:SI
REG_DEAD r191:SI
REG_DEAD r189:SI
Thus instruction 95 is loop invariant and be hoisted. For arm target, the loop
can be simplified into:
blt .L3
.L5:
add r2, r2, #1
ldr r3, [sp, r3, asl #2]
cmp r3, #0
bge .L5
uxtb r2, r2
