Generally speaking, this can only happen with unreachable code.
However, neglecting to check for this condition would lead us to loop
forever.
llvm-svn: 262284
Summary:
The code was simply ensuring that the catchpad's pred is its catchswitch,
which was letting cases slip through where the flow edge was the unwind
edge of the catchswitch rather than one of its catch clauses.
Reviewers: andrew.w.kaylor, rnk, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D16011
llvm-svn: 257275
Summary:
Funclet-based EH personalities/tables likely can't handle these, and they
can't be generated at source, so make them officially illegal in IR as
well.
Reviewers: andrew.w.kaylor, rnk, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15963
llvm-svn: 257274
Summary:
A funclet EH pad may be exited by an unwind edge, which may be a
cleanupret exiting its cleanuppad, an invoke exiting a funclet, or an
unwind out of a nested funclet transitively exiting its parent. Funclet
EH personalities require all such exceptional exits from a given funclet to
have the same unwind destination, and EH preparation / state numbering /
table generation implicitly depends on this. Formalize it as a rule of
the IR in the LangRef and verifier.
Reviewers: rnk, majnemer, andrew.w.kaylor
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15962
llvm-svn: 257273
Summary:
Funclet EH personalities require a tree-like nesting among funclets
(enforced by the ParentPad linkage in the IR), and also require that
unwind edges conform to certain rules with respect to the tree:
- An unwind edge may exit 0 or more ancestor pads
- An unwind edge must enter exactly one EH pad, which must be distinct
from any exited pads
- A cleanupret's edge must exit its cleanuppad
Describe these rules in the LangRef, and enforce them in the verifier.
Reviewers: rnk, majnemer, andrew.w.kaylor
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15961
llvm-svn: 257272
Summary:
The handler list must be nonempty and consist solely of CatchPads.
Reviewers: rnk, andrew.w.kaylor, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15842
llvm-svn: 256691
Summary: A catchswitch cannot be a parent of a cleanuppad or another catchswitch.
Reviewers: rnk, andrew.w.kaylor, majnemer
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D15841
llvm-svn: 256690
While we have successfully implemented a funclet-oriented EH scheme on
top of LLVM IR, our scheme has some notable deficiencies:
- catchendpad and cleanupendpad are necessary in the current design
but they are difficult to explain to others, even to seasoned LLVM
experts.
- catchendpad and cleanupendpad are optimization barriers. They cannot
be split and force all potentially throwing call-sites to be invokes.
This has a noticable effect on the quality of our code generation.
- catchpad, while similar in some aspects to invoke, is fairly awkward.
It is unsplittable, starts a funclet, and has control flow to other
funclets.
- The nesting relationship between funclets is currently a property of
control flow edges. Because of this, we are forced to carefully
analyze the flow graph to see if there might potentially exist illegal
nesting among funclets. While we have logic to clone funclets when
they are illegally nested, it would be nicer if we had a
representation which forbade them upfront.
Let's clean this up a bit by doing the following:
- Instead, make catchpad more like cleanuppad and landingpad: no control
flow, just a bunch of simple operands; catchpad would be splittable.
- Introduce catchswitch, a control flow instruction designed to model
the constraints of funclet oriented EH.
- Make funclet scoping explicit by having funclet instructions consume
the token produced by the funclet which contains them.
- Remove catchendpad and cleanupendpad. Their presence can be inferred
implicitly using coloring information.
N.B. The state numbering code for the CLR has been updated but the
veracity of it's output cannot be spoken for. An expert should take a
look to make sure the results are reasonable.
Reviewers: rnk, JosephTremoulet, andrew.w.kaylor
Differential Revision: http://reviews.llvm.org/D15139
llvm-svn: 255422
