From a225da97194d2316dedd9376e2888ef30b572a9c Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Mon, 11 Mar 2013 20:53:00 +0000
Subject: [PATCH] Don't remove a landing pad if the invoke requires a table
 entry.

An invoke may require a table entry. For instance, when the function it calls
is expected to throw.
<rdar://problem/13360379>

llvm-svn: 176827
---
 lib/Transforms/Utils/SimplifyCFG.cpp         | 20 ++++-
 test/Transforms/SimplifyCFG/trivial-throw.ll | 77 ++++++++++++++++++++
 2 files changed, 94 insertions(+), 3 deletions(-)
 create mode 100644 test/Transforms/SimplifyCFG/trivial-throw.ll

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index a5c5c22aa5a..681bf9c2b7a 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -2789,9 +2789,20 @@ bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) {
       return false;
 
   // Turn all invokes that unwind here into calls and delete the basic block.
+  bool InvokeRequiresTableEntry = false;
+  bool Changed = false;
   for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) {
     InvokeInst *II = cast<InvokeInst>((*PI++)->getTerminator());
+
+    if (II->hasFnAttr(Attribute::UWTable)) {
+      // Don't remove an `invoke' instruction if the ABI requires an entry into
+      // the table.
+      InvokeRequiresTableEntry = true;
+      continue;
+    }
+
     SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
+
     // Insert a call instruction before the invoke.
     CallInst *Call = CallInst::Create(II->getCalledValue(), Args, "", II);
     Call->takeName(II);
@@ -2811,11 +2822,14 @@ bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) {
 
     // Finally, delete the invoke instruction!
     II->eraseFromParent();
+    Changed = true;
   }
 
-  // The landingpad is now unreachable.  Zap it.
-  BB->eraseFromParent();
-  return true;
+  if (!InvokeRequiresTableEntry)
+    // The landingpad is now unreachable.  Zap it.
+    BB->eraseFromParent();
+
+  return Changed;
 }
 
 bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) {
diff --git a/test/Transforms/SimplifyCFG/trivial-throw.ll b/test/Transforms/SimplifyCFG/trivial-throw.ll
new file mode 100644
index 00000000000..ca2b5693e60
--- /dev/null
+++ b/test/Transforms/SimplifyCFG/trivial-throw.ll
@@ -0,0 +1,77 @@
+; RUN: opt -simplifycfg -S < %s | FileCheck %s
+; <rdar://problem/13360379>
+
+@_ZTVN10__cxxabiv117__class_type_infoE = external global i8*
+@_ZTS13TestException = linkonce_odr constant [16 x i8] c"13TestException\00"
+@_ZTI13TestException = linkonce_odr unnamed_addr constant { i8*, i8* } { i8* bitcast (i8** getelementptr inbounds (i8** @_ZTVN10__cxxabiv117__class_type_infoE, i64 2) to i8*), i8* getelementptr inbounds ([16 x i8]* @_ZTS13TestException, i32 0, i32 0) }
+
+define void @throw(i32 %n) #0 {
+entry:
+  %exception = call i8* @__cxa_allocate_exception(i64 1) #4
+  call void @__cxa_throw(i8* %exception, i8* bitcast ({ i8*, i8* }* @_ZTI13TestException to i8*), i8* null) #2
+  unreachable
+}
+
+define void @func() #0 {
+entry:
+; CHECK: func()
+; CHECK: invoke void @throw
+; CHECK-NOT: call void @throw
+  invoke void @throw(i32 42) #0
+          to label %exit unwind label %lpad
+
+lpad:
+  %tmp0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  resume { i8*, i32 } %tmp0
+
+exit:
+  invoke void @abort() #2
+          to label %invoke.cont unwind label %lpad1
+
+invoke.cont:
+  unreachable
+
+lpad1:
+  %tmp1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          catch i8* bitcast ({ i8*, i8* }* @_ZTI13TestException to i8*)
+  %tmp2 = extractvalue { i8*, i32 } %tmp1, 1
+  %tmp3 = call i32 @llvm.eh.typeid.for(i8* bitcast ({ i8*, i8* }* @_ZTI13TestException to i8*)) #4
+  %matches = icmp eq i32 %tmp2, %tmp3
+  br i1 %matches, label %catch, label %eh.resume
+
+catch:
+  ret void
+
+eh.resume:
+  resume { i8*, i32 } %tmp1
+}
+
+define linkonce_odr hidden void @__clang_call_terminate(i8*) #1 {
+  %2 = call i8* @__cxa_begin_catch(i8* %0) #4
+  call void @_ZSt9terminatev() #5
+  unreachable
+}
+
+declare void @abort() #2
+
+declare i32 @llvm.eh.typeid.for(i8*) #3
+
+declare void @__cxa_end_catch()
+
+declare i8* @__cxa_allocate_exception(i64)
+
+declare i32 @__gxx_personality_v0(...)
+
+declare void @__cxa_throw(i8*, i8*, i8*)
+
+declare i8* @__cxa_begin_catch(i8*)
+
+declare void @_ZSt9terminatev()
+
+attributes #0 = { ssp uwtable }
+attributes #1 = { noinline noreturn nounwind }
+attributes #2 = { noreturn }
+attributes #3 = { nounwind readnone }
+attributes #4 = { nounwind }
+attributes #5 = { noreturn nounwind }