This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: threading jumps makes niter changed from INTEGER_CST to chrec_dont_know
- From: Jeff Law <law at redhat dot com>
- To: Eric Fisher <joefoxreal at gmail dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Tue, 05 Jan 2010 10:12:57 -0700
- Subject: Re: threading jumps makes niter changed from INTEGER_CST to chrec_dont_know
- References: <d6afecde1001050046l4363043bt504be33a6cec2cf3@mail.gmail.com>
On 01/05/10 01:46, Eric Fisher wrote:
Hi,
I found that sometimes -fno-tree-dominator-opts will bring a big speed
promotion. This is because that pass_dominator tries to thread jumps.
But sometimes this will cause that the loop's exit bb does not
dominator its latch bb again. Then pass_complete_unroll is unable to
know the exact number of loop iteration and will not unroll the loop
completely again
Please file a bug report with a complete testcase so that we can see
what's happening rather than trying to speculate.
jeff