From d5b7f2b62cdb3a14162c57e27c06a27dda9a78c4 Mon Sep 17 00:00:00 2001
From: Bill Wendling <isanbard@gmail.com>
Date: Sat, 19 Oct 2013 11:27:12 +0000
Subject: [PATCH] Perform an intelligent splice of the predecessor with the
 single successor.

If the predecessor's being spliced into a landing pad, then we need the PHIs to
come first and the rest of the predecessor's code to come *after* the landing
pad instruction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193035 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Utils/Local.cpp                | 15 ++++++-
 .../JumpThreading/landing-pad-splicing.ll     | 43 +++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 test/Transforms/JumpThreading/landing-pad-splicing.ll

diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index 82b8da3a107..78217c8efa3 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -503,7 +503,19 @@ void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, Pass *P) {
 
   // Splice all the instructions from PredBB to DestBB.
   PredBB->getTerminator()->eraseFromParent();
-  DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList());
+
+  // First splice over the PHI nodes.
+  BasicBlock::iterator PI = PredBB->begin();
+  while (isa<PHINode>(PI))
+    ++PI;
+
+  if (PI != PredBB->begin())
+    DestBB->getInstList().splice(DestBB->begin(), PredBB->getInstList(),
+                                 PredBB->begin(), PI);
+
+  // Now splice over the rest of the instructions.
+  DestBB->getInstList().splice(DestBB->getFirstInsertionPt(),
+                               PredBB->getInstList(), PI, PredBB->end());
 
   if (P) {
     DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>();
@@ -513,6 +525,7 @@ void llvm::MergeBasicBlockIntoOnlyPred(BasicBlock *DestBB, Pass *P) {
       DT->eraseNode(PredBB);
     }
   }
+
   // Nuke BB.
   PredBB->eraseFromParent();
 }
diff --git a/test/Transforms/JumpThreading/landing-pad-splicing.ll b/test/Transforms/JumpThreading/landing-pad-splicing.ll
new file mode 100644
index 00000000000..1ac0209270b
--- /dev/null
+++ b/test/Transforms/JumpThreading/landing-pad-splicing.ll
@@ -0,0 +1,43 @@
+; RUN: opt -S -jump-threading < %s -disable-output
+; PR17621
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.8.0"
+
+declare void @_ZN1F7doApplyEv() unnamed_addr readnone align 2
+
+define void @_Z3fn1v() uwtable {
+entry:
+  store i32 0, i32* undef, align 4
+  invoke void @_ZN1F7doApplyEv()
+          to label %_ZN1D5applyEv.exit unwind label %lpad1
+
+_ZN1D5applyEv.exit:
+  invoke void @_ZN1F10insertTextEv()
+          to label %invoke.cont7 unwind label %lpad1
+
+invoke.cont7:
+  ret void
+
+lpad1:
+  %tmp1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  %tmp2 = load i32* undef, align 4
+  %tobool.i.i.i = icmp eq i32 %tmp2, 0
+  br i1 %tobool.i.i.i, label %_ZN1BI1FED1Ev.exit, label %if.then.i.i.i
+
+if.then.i.i.i:
+  br i1 undef, label %_ZN1BI1FED1Ev.exit, label %delete.notnull.i.i.i
+
+delete.notnull.i.i.i:
+  unreachable
+
+_ZN1BI1FED1Ev.exit:
+  br label %eh.resume
+
+eh.resume:
+  resume { i8*, i32 } undef
+}
+
+declare i32 @__gxx_personality_v0(...)
+
+declare void @_ZN1F10insertTextEv()