From 521fc5bcd73489f604a0b3251247c5ef21b5a0a5 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Wed, 23 Nov 2011 08:23:54 +0000
Subject: [PATCH] Handle the case of a no-return invoke correctly. It actually
 still has successors, they just are all landing pad successors. We handle
 this the same way as no successors. Comments attached for the next person to
 wade through here and another lovely test case courtesy of Benjamin Kramer's
 bugpoint reduction.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145098 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MachineBasicBlock.cpp   |  8 ++++++++
 test/CodeGen/X86/block-placement.ll | 24 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/lib/CodeGen/MachineBasicBlock.cpp b/lib/CodeGen/MachineBasicBlock.cpp
index f05b6c1eb97..b9d1ef7c68c 100644
--- a/lib/CodeGen/MachineBasicBlock.cpp
+++ b/lib/CodeGen/MachineBasicBlock.cpp
@@ -305,6 +305,14 @@ void MachineBasicBlock::updateTerminator() {
         assert(!TBB && "Found more than one non-landing-pad successor!");
         TBB = *SI;
       }
+
+      // If there is no non-landing-pad successor, the block has no
+      // fall-through edges to be concerned with.
+      if (!TBB)
+        return;
+
+      // Finally update the unconditional successor to be reached via a branch
+      // if it would not be reached by fallthrough.
       if (!isLayoutSuccessor(TBB))
         TII->InsertBranch(*this, TBB, 0, Cond, dl);
     }
diff --git a/test/CodeGen/X86/block-placement.ll b/test/CodeGen/X86/block-placement.ll
index 05d6f8138f9..c03b03ed02d 100644
--- a/test/CodeGen/X86/block-placement.ll
+++ b/test/CodeGen/X86/block-placement.ll
@@ -504,6 +504,30 @@ loop:
   br label %loop
 }
 
+declare void @fake_throw() noreturn
+
+define void @test_eh_throw() {
+; For blocks containing a 'throw' (or similar functionality), we have
+; a no-return invoke. In this case, only EH successors will exist, and
+; fallthrough simply won't occur. Make sure we don't crash trying to update
+; terminators for such constructs.
+;
+; CHECK: test_eh_throw
+; CHECK: %entry
+; CHECK: %cleanup
+
+entry:
+  invoke void @fake_throw() to label %continue unwind label %cleanup
+
+continue:
+  unreachable
+
+cleanup:
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  unreachable
+}
+
 define void @test_unnatural_cfg_backwards_inner_loop() {
 ; Test that when we encounter an unnatural CFG structure after having formed
 ; a chain for an inner loop which happened to be laid out backwards we don't