On 18/04/13 09:20, Steven Bosscher wrote:
On Thu, Apr 18, 2013 at 7:34 AM, Bin Cheng wrote:
Hi,
Before thumb1_reorg, ARM backend uses peephole to save comparison
instructions when a flag setting move is found before branch instruction.
Since we are using thumb1_reog now, it can be extended to catch more
opportunities by searching flag setting move instruction before branch,
rather than only the exact one before branch.
For example:
mov r0, r1
//other insns does not kill r0
branch if (r0 == 0)
//other insns
Tested on thumb1, is it OK?
Isn't this something you could use compare-elim.c for instead of a
target specific pass?
Ciao!
Steven
I haven't looked at compare-elim, but probably not. Thumb1 doesn't use
cc1 and doesn't expose flag setting instructions in a MI manner (since
add instructions clobber the flags). As such it needs private back-end
data to work out what's safe.
