From a4824774dc6cc54a8a69fec74eea6e2ed415a109 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 5 Jan 2016 06:27:50 +0000
Subject: [PATCH] [SimplifyCFG] Remove redundant catchpads

Remove duplicate catchpad handlers from a catchswitch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256814 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/Local.cpp                   | 19 +++++++++++++++++--
 test/Transforms/SimplifyCFG/wineh-unreachable.ll | 18 ++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index e75163f323d..3845ca2e7e5 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -1305,8 +1305,9 @@ static bool markAliveBlocks(Function &F,
       }
     }
 
-    // Turn invokes that call 'nounwind' functions into ordinary calls.
-    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
+    TerminatorInst *Terminator = BB->getTerminator();
+    if (auto *II = dyn_cast<InvokeInst>(Terminator)) {
+      // Turn invokes that call 'nounwind' functions into ordinary calls.
       Value *Callee = II->getCalledValue();
       if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
         changeToUnreachable(II, true);
@@ -1321,6 +1322,20 @@ static bool markAliveBlocks(Function &F,
           changeToCall(II);
         Changed = true;
       }
+    } else if (auto *CatchSwitch = dyn_cast<CatchSwitchInst>(Terminator)) {
+      // Remove catchpads which cannot be reached.
+      SmallPtrSet<BasicBlock *, 4> HandlersSeen;
+      for (CatchSwitchInst::handler_iterator I = CatchSwitch->handler_begin(),
+                                             E = CatchSwitch->handler_end();
+           I != E; ++I) {
+        BasicBlock *HandlerBB = *I;
+        if (!HandlersSeen.insert(HandlerBB).second) {
+          CatchSwitch->removeHandler(I);
+          --I;
+          --E;
+          Changed = true;
+        }
+      }
     }
 
     Changed |= ConstantFoldTerminator(BB, true);
diff --git a/test/Transforms/SimplifyCFG/wineh-unreachable.ll b/test/Transforms/SimplifyCFG/wineh-unreachable.ll
index 670119467da..d871e17b6b0 100644
--- a/test/Transforms/SimplifyCFG/wineh-unreachable.ll
+++ b/test/Transforms/SimplifyCFG/wineh-unreachable.ll
@@ -81,3 +81,21 @@ catch.body:
 exit:
   unreachable
 }
+
+; CHECK-LABEL: define void @test6()
+define void @test6() personality i8* bitcast (void ()* @Personality to i8*) {
+entry:
+  invoke void @f()
+          to label %exit unwind label %catch.pad
+
+catch.pad:
+  %cs1 = catchswitch within none [label %catch.body, label %catch.body] unwind to caller
+  ; CHECK: catchswitch within none [label %catch.body] unwind to caller
+
+catch.body:
+  %catch = catchpad within %cs1 [i8* null, i32 0, i8* null]
+  catchret from %catch to label %exit
+
+exit:
+  ret void
+}
-- 
2.11.0