llvm/test/CodeGen
Chandler Carruth 03300ecaee Move the handling of unanalyzable branches out of the loop-driven chain
formation phase and into the initial walk of the basic blocks. We
essentially pre-merge all blocks where unanalyzable fallthrough exists,
as we won't be able to update the terminators effectively after any
reorderings. This is quite a bit more principled as there may be CFGs
where the second half of the unanalyzable pair has some analyzable
predecessor that gets placed first. Then it may get placed next,
implicitly breaking the unanalyzable branch even though we never even
looked at the part that isn't analyzable. I've included a test case that
triggers this (thanks Benjamin yet again!), and I'm hoping to synthesize
some more general ones as I dig into related issues.

Also, to make this new scheme work we have to be able to handle branches
into the middle of a chain, so add this check. We always fallback on the
incoming ordering.

Finally, this starts to really underscore a known limitation of the
current implementation -- we don't consider broken predecessors when
merging successors. This can caused major missed opportunities, and is
something I'm planning on looking at next (modulo more bug reports).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144994 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-19 10:26:02 +00:00
..
ARM When fast iseling a GEP, accumulate the offset rather than emitting a series of 2011-11-17 07:15:58 +00:00
CBackend
CellSPU Remove histogram tests. 2011-11-12 22:39:40 +00:00
CPP
Generic
MBlaze
Mips
MSP430
PowerPC
PTX allow non-device function calls in PTX when natively handling device-side printf 2011-11-11 14:45:12 +00:00
SPARC
Thumb
Thumb2 Add vmov.f32 to materialize f32 immediate splats which cannot be handled by 2011-11-15 02:12:34 +00:00
X86 Move the handling of unanalyzable branches out of the loop-driven chain 2011-11-19 10:26:02 +00:00
XCore