Index: lib/CodeGen/MachineBlockPlacement.cpp
===================================================================
--- lib/CodeGen/MachineBlockPlacement.cpp
+++ lib/CodeGen/MachineBlockPlacement.cpp
@@ -1944,6 +1944,22 @@
   if (ExitIt == LoopChain.end())
     return;
 
+  // If the header has viable fallthrough and our exit candidate is
+  // a predecessor of next element in built loop chain then rotation
+  // will introduce an unnecessary branch because before we had a fallthrough
+  // from exit candidate but now we will have a branch. This branch will not be
+  // extra one only if the last block in a chain is a predecessor of first
+  // element in chain, because then rotation will eliminate one branch.
+  if (ViableTopFallthrough) {
+    MachineBasicBlock *NextBlockInChain = *std::next(ExitIt);
+    MachineBasicBlock *Bottom = *std::prev(LoopChain.end());
+    if (NextBlockInChain->isPredecessor(ExitingBB))
+      if (!Top->isPredecessor(Bottom))
+        return;
+  }
+
+  DEBUG(dbgs() << "Do loop rotation with new exit block "
+               << getBlockName(ExitingBB) << "\n");
   std::rotate(LoopChain.begin(), std::next(ExitIt), LoopChain.end());
 }
 
Index: test/CodeGen/X86/block-placement.ll
===================================================================
--- test/CodeGen/X86/block-placement.ll
+++ test/CodeGen/X86/block-placement.ll
@@ -354,6 +354,7 @@
 ; single-source GCC.
 ; CHECK-LABEL: unnatural_cfg2
 ; CHECK: %entry
+; CHECK: %loop.header
 ; CHECK: %loop.body1
 ; CHECK: %loop.body2
 ; CHECK: %loop.body4
@@ -361,7 +362,6 @@
 ; CHECK: %loop.inner2.begin
 ; CHECK: %loop.body3
 ; CHECK: %loop.inner1.begin
-; CHECK: %loop.header
 ; CHECK: %bail
 
 entry:
@@ -1491,6 +1491,54 @@
   ret void
 }
 
+define i32 @not_rotate_if_extra_branch(i32 %count) {
+; Test checks that there is no loop rotation
+; if it introduces extra branch.
+; Specifically in this case because best exit is .header
+; but it has fallthrough to .middle block and last block in
+; loop chain .slow does not have afallthrough to .header.
+; CHECK-LABEL: not_rotate_if_extra_branch
+; CHECK: %.entry
+; CHECK: %.header
+; CHECK: %.middle
+; CHECK: %.backedge
+; CHECK: %.slow
+; CHECK: %.bailout
+; CHECK: %.stop
+.entry:
+  %sum.0 = shl nsw i32 %count, 1
+  br label %.header
+
+.header:
+  %i = phi i32 [ %i.1, %.backedge ], [ 0, %.entry ]
+  %sum = phi i32 [ %sum.1, %.backedge ], [ %sum.0, %.entry ]
+  %is_exc = icmp sgt i32 %i, 9000000
+  br i1 %is_exc, label %.bailout, label %.middle, !prof !13
+
+.bailout:
+  %sum.2 = add nsw i32 %count, 1
+  br label %.stop
+
+.middle:
+  %pr.1 = and i32 %i, 1023
+  %pr.2 = icmp eq i32 %pr.1, 0
+  br i1 %pr.2, label %.slow, label %.backedge, !prof !14
+
+.slow:
+  tail call void @effect(i32 %sum)
+  br label %.backedge
+
+.backedge:
+  %sum.1 = add nsw i32 %i, %sum
+  %i.1 = add nsw i32 %i, 1
+  %end = icmp slt i32 %i.1, %count
+  br i1 %end, label %.header, label %.stop, !prof !15
+
+.stop:
+  %sum.phi = phi i32 [ %sum.1, %.backedge ], [ %sum.2, %.bailout ]
+  ret i32 %sum.phi
+}
+
 declare void @effect(i32)
 
 !5 = !{!"branch_weights", i32 84, i32 16}
@@ -1501,3 +1549,6 @@
 !10 = !{!"branch_weights", i32 90, i32 10}
 !11 = !{!"branch_weights", i32 1, i32 1}
 !12 = !{!"branch_weights", i32 5, i32 3}
+!13 = !{!"branch_weights", i32 1, i32 1}
+!14 = !{!"branch_weights", i32 1, i32 1023}
+!15 = !{!"branch_weights", i32 4095, i32 1}
Index: test/CodeGen/X86/code_placement_cold_loop_blocks.ll
===================================================================
--- test/CodeGen/X86/code_placement_cold_loop_blocks.ll
+++ test/CodeGen/X86/code_placement_cold_loop_blocks.ll
@@ -37,7 +37,7 @@
   ret void
 }
 
-define void @nested_loop_0() !prof !1 {
+define void @nested_loop_0(i1 %flag) !prof !1 {
 ; Test if a block that is cold in the inner loop but not cold in the outer loop
 ; will merged to the outer loop chain.
 ;
@@ -68,8 +68,7 @@
 
 if.else:
   call void @e()
-  %call2 = call zeroext i1 @a()
-  br i1 %call2, label %header2, label %header, !prof !3
+  br i1 %flag, label %header2, label %header, !prof !3
 
 end:
   call void @f()