About Loop Pattern ----GCC porting

["redriver jiang" <jiangpeople at gmail dot com>]

Hello:
      I am Jiang Hongjiang and recently I am porting the GCC backend
to a DSP, and get puzzled about the "decrement_and_branch_until_zero"
pattern.By Reading the GCC source, I find that this pattern is used in
loop optimization, and it's used under the condition of defining the
"doloop_end" pattern. Inspired by the c4x machine description file(
c4x.md), I defined the "doloop_end" pattern using "define_expand", and
generate the "decrement_and_branch_until_zero" insn in the preparation
statements. Right now the GCC can generate the
"decrement_and_branch_until_zero" insns and its related assemble
insn(in my platform it is "DJNZ Rn,lable"), but I find that the GCC
remains other insns(the cmp insns and other) unchanged. How do you
delete the "CMP" insn and other insn in the loop while using the
"decrement_and_branch_until_zero" pattern? The accessory demonstrates
a example.


Thanks!

Attachment: Example.txt
Description: Text document