[WinEH] Fix catchpad pred verification

[JosephTremoulet]

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.

[majnemer]

LGTM

lib/IR/Verifier.cpp

if (auto *LPI = dyn_cast<LandingPadInst>(&I)) {
     return;
   }
   if (auto *CPI = dyn_cast<CatchPadInst>(&I)) {
     if (!pred_empty(BB))
       Assert(BB->getUniquePredecessor() == CPI->getCatchSwitch()->getParent(),
              "Block containg CatchPadInst must be jumped to "
              "only by its catchswitch.",
              CPI);
+    Assert(BB != CPI->getCatchSwitch()->getUnwindDest(),
+           "Catchswitch cannot unwind to one of its catchpads",
+           CPI->getCatchSwitch(), CPI);
     return;
   }
 
   // Verify that each pred has a legal terminator with a legal to/from EH
   // pad relationship.
   Instruction *ToPad = &I;
   Value *ToPadParent = getParentPad(ToPad);
   for (BasicBlock *PredBB : predecessors(BB)) {

test/Verifier/invalid-eh.ll

 ; RUN: sed -e s/.T12:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK12 %s
 ; RUN: sed -e s/.T13:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK13 %s
 ; RUN: sed -e s/.T14:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK14 %s
 ; RUN: sed -e s/.T15:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK15 %s
 ; RUN: sed -e s/.T16:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK16 %s
 ; RUN: sed -e s/.T17:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK17 %s
 ; RUN: sed -e s/.T18:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK18 %s
 ; RUN: sed -e s/.T19:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK19 %s
+; RUN: sed -e s/.T20:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK20 %s
+; RUN: sed -e s/.T21:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK21 %s
 
 declare void @g()
 
 ;T1: define void @f() {
 ;T1:   entry:
 ;T1:     catchret from undef to label %next
 ;T1:     ; CHECK1: CatchReturnInst needs to be provided a CatchPad
 ;T1:   next:

 ;T19:     ; CHECK19-NEXT: invoke void @g() [ "funclet"(token %innerpad) ]
 ;T19:     ; CHECK19-NEXT:         to label %unreachable unwind label %green
 ;T19:     ; CHECK19-NEXT: %greenswitch = catchswitch within none [label %catch] unwind label %blue
 ;T19:     ; CHECK19-NEXT: %bluepad = cleanuppad within none []
 ;T19:     ; CHECK19-NEXT: cleanupret from %bluepad unwind label %red
 ;T19:   unreachable:
 ;T19:     unreachable
 ;T19: }
+
+;T20: define void @f() personality void ()* @g {
+;T20:   entry:
+;T20:     ret void
+;T20:   switch:
+;T20:     %cs = catchswitch within none [label %catch] unwind label %catch
+;T20:     ; CHECK20: Catchswitch cannot unwind to one of its catchpads
+;T20:     ; CHECK20-NEXT: %cs = catchswitch within none [label %catch] unwind label %catch
+;T20:     ; CHECK20-NEXT: %cp = catchpad within %cs [i32 4]
+;T20:   catch:
+;T20:     %cp = catchpad within %cs [i32 4]
+;T20:     unreachable
+;T20: }
+
+;T21: define void @f() personality void ()* @g {
+;T21:   entry:
+;T21:     ret void
+;T21:   switch:
+;T21:     %cs = catchswitch within none [label %catch1] unwind label %catch2
+;T21:     ; CHECK21: Catchswitch cannot unwind to one of its catchpads
+;T21:     ; CHECK21-NEXT: %cs = catchswitch within none [label %catch1] unwind label %catch2
+;T21:     ; CHECK21-NEXT: %cp2 = catchpad within %cs [i32 2]
+;T21:   catch1:
+;T21:     %cp1 = catchpad within %cs [i32 1]
+;T21:     unreachable
+;T21:   catch2:
+;T21:     %cp2 = catchpad within %cs [i32 2]
+;T21:     unreachable
+;T21: }