Index: lib/CodeGen/IfConversion.cpp
===================================================================
--- lib/CodeGen/IfConversion.cpp
+++ lib/CodeGen/IfConversion.cpp
@@ -1723,11 +1723,15 @@
   // Skip past the dups on each side separately since there may be
   // differing dbg_value entries.
   for (unsigned i = 0; i < NumDups1; ++DI1) {
+    if (DI1 == MBB1.end())
+      break;
     if (!DI1->isDebugValue())
       ++i;
   }
   while (NumDups1 != 0) {
     ++DI2;
+    if (DI2 == MBB2.end())
+      break;
     if (!DI2->isDebugValue())
       --NumDups1;
   }
@@ -1762,6 +1766,12 @@
   }
   MBB1.erase(DI1, MBB1.end());
 
+  // Identical blocks, already moved all the instructions up.
+  if (MBB1.empty() && MBB2.empty()) {
+    BBI.BB->removeSuccessor(&MBB1, true);
+    BBI.BB->removeSuccessor(&MBB2, true);
+    return true;
+  }
   DI2 = BBI2->BB->end();
   // The branches have been checked to match. Skip over the branch in the false
   // block so that we don't try to predicate it.
Index: test/CodeGen/MIR/PowerPC/ifcvt-diamond-ret.mir
===================================================================
--- /dev/null
+++ test/CodeGen/MIR/PowerPC/ifcvt-diamond-ret.mir
@@ -0,0 +1,34 @@
+# RUN: llc -mtriple=powerpc64le-unknown-linux-gnu -run-pass=if-converter %s -o - | FileCheck %s
+---
+name:           foo
+body:           |
+  bb.0:
+  liveins: $x0, $x3
+  successors: %bb.1(0x40000000), %bb.2(0x40000000)
+
+  dead renamable $x3 = ANDIo8 killed renamable $x3, 1, implicit-def dead $cr0, implicit-def $cr0gt
+  $cr2lt = CROR $cr0gt, $cr0gt
+  BCn killed renamable $cr2lt, %bb.2
+  B %bb.1
+
+  bb.1:
+    renamable $x3 = LIS8 4096
+    MTLR8 $x0, implicit-def $lr8
+    BLR8 implicit $lr8, implicit $rm, implicit $x3
+
+  bb.2:
+    renamable $x3 = LIS8 4096
+    MTLR8 $x0, implicit-def $lr8
+    BLR8 implicit $lr8, implicit $rm, implicit $x3
+...
+
+# Diamond testcase with equivalent branches terminating in returns.
+
+# CHECK: body:             |          
+# CHECK:  bb.0:
+# CHECK:    dead renamable $x3 = ANDIo8 killed renamable $x3, 1, implicit-def dead $cr0, implicit-def $cr0gt
+# CHECK:    $cr2lt = CROR $cr0gt, $cr0gt
+# CHECK:    renamable $x3 = LIS8 4096
+# CHECK:    MTLR8 $x0, implicit-def $lr8
+# CHECK:    BLR8 implicit $lr8, implicit $rm, implicit $x3
+