On 11/28/2016 03:00 PM, David Malcolm wrote:
On Mon, 2016-11-28 at 14:44 -0700, Jeff Law wrote:
On 11/23/2016 04:55 PM, Segher Boessenkool wrote:
Combine can turn a conditional trap into an unconditional trap. If
it
does that it should make the code after it unreachable (an
unconditional
trap should be the last insn in its bb, and that bb has no
successors).
This patch seems to work. It is hard to be sure, this is very hard
to
trigger. Quite a few other passes look like they need something
similar
as well, but I don't see anything else handling it yet either.
How does this look? Any better ideas?
It's probably a reasonable place to start as there's lots of
similarities to converting a conditional branch to an unconditional.
Like you I worry there may be other instances of this issue may be
lurking.
The possibility of having a conditional trap in the IL turn into an
unconditional trap has always been there. As you note, it's somewhat
difficult to trigger since the SSA optimizers ought to
expose/optimize
this long before we get to RTL.
Could the RTL frontend be of use here?
Maybe -- but only on targets where we have the right insns in the target
machine description.
jeff
