[IR] Reformulate LLVM's EH funclet IR

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

1 files changed, 10 insertions, 11 deletions

diff --git a/llvm/test/Transforms/Inline/PR25155.ll b/llvm/test/Transforms/Inline/PR25155.ll
index f2a9ec32fda..aed9a58ab3d 100644
--- a/llvm/test/Transforms/Inline/PR25155.ll
+++ b/llvm/test/Transforms/Inline/PR25155.ll
@@ -8,21 +8,23 @@ entry:
           to label %try.cont unwind label %catch.dispatch
 
 catch.dispatch:                                   ; preds = %entry
-  %0 = catchpad [i8* null, i32 64, i8* null]
-          to label %catch unwind label %catchendblock
+  %cs1 = catchswitch within none [label %catch] unwind to caller
 
 catch:                                            ; preds = %catch.dispatch
+  %0 = catchpad within %cs1 [i8* null, i32 64, i8* null]
   invoke void @dtor()
-          to label %invoke.cont.1 unwind label %catchendblock
+          to label %invoke.cont.1 unwind label %ehcleanup
 
 invoke.cont.1:                                    ; preds = %catch
-  catchret %0 to label %try.cont
+  catchret from %0 to label %try.cont
 
 try.cont:                                         ; preds = %entry, %invoke.cont.1
   ret void
 
-catchendblock:                                    ; preds = %catch, %catch.dispatch
-  catchendpad unwind to caller
+ehcleanup:
+  %cp2 = cleanuppad within none []
+  call void @g()
+  cleanupret from %cp2 unwind to caller
 }
 
 ; CHECK-LABEL:  define void @f(
@@ -31,10 +33,7 @@ catchendblock:                                    ; preds = %catch, %catch.dispa
 ; CHECK:                 to label %dtor.exit unwind label %terminate.i
 
 ; CHECK:       terminate.i:
-; CHECK-NEXT:    terminatepad [void ()* @terminate] unwind label %catchendblock
-
-; CHECK:       catchendblock:
-; CHECK-NEXT:    catchendpad unwind to caller
+; CHECK-NEXT:    terminatepad within %0 [void ()* @terminate] unwind label %ehcleanup
 
 declare i32 @__CxxFrameHandler3(...)
 
@@ -47,7 +46,7 @@ invoke.cont:                                      ; preds = %entry
   ret void
 
 terminate:                                        ; preds = %entry
-  terminatepad [void ()* @terminate] unwind to caller
+  terminatepad within none [void ()* @terminate] unwind to caller
 }
 
 declare void @g()