[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, 28 insertions, 101 deletions

diff --git a/llvm/test/Feature/exception.ll b/llvm/test/Feature/exception.ll
index c6c436ae83d..05dbfe89645 100644
--- a/llvm/test/Feature/exception.ll
+++ b/llvm/test/Feature/exception.ll
@@ -31,8 +31,8 @@ entry:
   invoke void @_Z3quxv() optsize
           to label %exit unwind label %pad
 pad:
-  %cp = cleanuppad [i7 4]
-  cleanupret %cp unwind to caller
+  %cp = cleanuppad within none [i7 4]
+  cleanupret from %cp unwind to caller
 exit:
   ret void
 }
@@ -43,9 +43,9 @@ entry:
   invoke void @_Z3quxv() optsize
           to label %exit unwind label %pad
 cleanup:
-  cleanupret %cp unwind label %pad
+  cleanupret from %cp unwind label %pad
 pad:
-  %cp = cleanuppad []
+  %cp = cleanuppad within none []
   br label %cleanup
 exit:
   ret void
@@ -57,9 +57,9 @@ entry:
   invoke void @_Z3quxv() optsize
           to label %exit unwind label %pad
 cleanup:
-  cleanupret %0 unwind label %pad
+  cleanupret from %0 unwind label %pad
 pad:
-  %0 = cleanuppad []
+  %0 = cleanuppad within none []
   br label %cleanup
 exit:
   ret void
@@ -70,12 +70,10 @@ entry:
   invoke void @_Z3quxv() optsize
           to label %exit unwind label %pad
 pad:
-  %cp = catchpad [i7 4]
-          to label %catch unwind label %endpad
+  %cs1 = catchswitch within none [label %catch] unwind to caller
 catch:
-  catchret %cp to label %exit
-endpad:
-  catchendpad unwind to caller
+  %cp = catchpad within %cs1 [i7 4]
+  catchret from %cp to label %exit
 exit:
   ret void
 }
@@ -85,13 +83,13 @@ define void @catchret1() personality i32 (...)* @__gxx_personality_v0 {
 entry:
   invoke void @_Z3quxv() optsize
           to label %exit unwind label %pad
-catch:
-  catchret %cp to label %exit
+catchret:
+  catchret from %cp to label %exit
 pad:
-  %cp = catchpad []
-          to label %catch unwind label %endpad
-endpad:
-  catchendpad unwind to caller
+  %cs1 = catchswitch within none [label %catch] unwind to caller
+catch:
+  %cp = catchpad within %cs1 [i7 4]
+  br label %catchret
 exit:
   ret void
 }
@@ -101,13 +99,13 @@ define void @catchret2() personality i32 (...)* @__gxx_personality_v0 {
 entry:
   invoke void @_Z3quxv() optsize
           to label %exit unwind label %pad
-catch:
-  catchret %0 to label %exit
+catchret:
+  catchret from %0 to label %exit
 pad:
-  %0 = catchpad []
-          to label %catch unwind label %endpad
-endpad:
-  catchendpad unwind to caller
+  %cs1 = catchswitch within none [label %catch] unwind to caller
+catch:
+  %0 = catchpad within %cs1 [i7 4]
+  br label %catchret
 exit:
   ret void
 }
@@ -117,9 +115,10 @@ entry:
   invoke void @_Z3quxv() optsize
           to label %exit unwind label %bb2
 bb2:
-  catchpad [i7 4] to label %exit unwind label %bb3
-bb3:
-  catchendpad unwind to caller
+  %cs1 = catchswitch within none [label %catch] unwind to caller
+catch:
+  catchpad within %cs1 [i7 4]
+  br label %exit
 exit:
   ret i8 0
 }
@@ -132,7 +131,7 @@ try.cont:
   invoke void @_Z3quxv() optsize
           to label %try.cont unwind label %bb
 bb:
-  terminatepad [i7 4] unwind label %bb
+  terminatepad within none [i7 4] unwind label %bb
 }
 
 define void @terminatepad1() personality i32 (...)* @__gxx_personality_v0 {
@@ -143,7 +142,7 @@ try.cont:
   invoke void @_Z3quxv() optsize
           to label %try.cont unwind label %bb
 bb:
-  terminatepad [i7 4] unwind to caller
+  terminatepad within none [i7 4] unwind to caller
 }
 
 define void @cleanuppad() personality i32 (...)* @__gxx_personality_v0 {
@@ -154,78 +153,6 @@ try.cont:
   invoke void @_Z3quxv() optsize
           to label %try.cont unwind label %bb
 bb:
-  cleanuppad [i7 4]
-  ret void
-}
-
-define void @catchendpad0() personality i32 (...)* @__gxx_personality_v0 {
-entry:
-  br label %try.cont
-
-try.cont:
-  invoke void @_Z3quxv() optsize
-          to label %try.cont unwind label %bb
-bb:
-  catchendpad unwind label %bb
-}
-
-define void @catchendpad1() personality i32 (...)* @__gxx_personality_v0 {
-entry:
-  br label %try.cont
-
-try.cont:
-  invoke void @_Z3quxv() optsize
-          to label %try.cont unwind label %bb
-bb:
-  catchendpad unwind to caller
-}
-
-define void @cleanupendpad0() personality i32 (...)* @__gxx_personality_v0 {
-entry:
-  invoke void @_Z3quxv() optsize
-          to label %exit unwind label %pad
-pad:
-  %cp = cleanuppad [i7 4]
-  invoke void @_Z3quxv() optsize
-          to label %stop unwind label %endpad
-stop:
-  unreachable
-endpad:
-  cleanupendpad %cp unwind label %pad
-exit:
-  ret void
-}
-
-; forward ref by name
-define void @cleanupendpad1() personality i32 (...)* @__gxx_personality_v0 {
-entry:
-  invoke void @_Z3quxv() optsize
-          to label %exit unwind label %pad
-endpad:
-  cleanupendpad %cp unwind to caller
-pad:
-  %cp = cleanuppad []
-  invoke void @_Z3quxv() optsize
-          to label %stop unwind label %endpad
-stop:
-  unreachable
-exit:
-  ret void
-}
-
-; forward ref by ID
-define void @cleanupendpad2() personality i32 (...)* @__gxx_personality_v0 {
-entry:
-  invoke void @_Z3quxv() optsize
-          to label %exit unwind label %pad
-endpad:
-  cleanupendpad %0 unwind label %pad
-pad:
-  %0 = cleanuppad []
-  invoke void @_Z3quxv() optsize
-          to label %stop unwind label %endpad
-stop:
-  unreachable
-exit:
+  cleanuppad within none [i7 4]
   ret void
 }