Index: llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp
+++ llvm/trunk/lib/Target/ARM/ARMTargetTransformInfo.cpp
@@ -586,34 +586,53 @@
   if (!ST->isMClass())
     return BasicTTIImplBase::getUnrollingPreferences(L, SE, UP);
 
-  // Only enable on Thumb-2 targets for simple loops.
-  if (!ST->isThumb2() || L->getNumBlocks() != 1)
-    return;
-
   // Disable loop unrolling for Oz and Os.
   UP.OptSizeThreshold = 0;
   UP.PartialOptSizeThreshold = 0;
-  BasicBlock *BB = L->getLoopLatch();
-  if (BB->getParent()->optForSize())
+  if (L->getHeader()->getParent()->optForSize())
+    return;
+
+  // Only enable on Thumb-2 targets.
+  if (!ST->isThumb2())
+    return;
+
+  SmallVector<BasicBlock*, 4> ExitingBlocks;
+  L->getExitingBlocks(ExitingBlocks);
+  DEBUG(dbgs() << "Loop has:\n"
+      << "Blocks: " << L->getNumBlocks() << "\n"
+      << "Exit blocks: " << ExitingBlocks.size() << "\n");
+
+  // Only allow another exit other than the latch. This acts as an early exit
+  // as it mirrors the profitability calculation of the runtime unroller.
+  if (ExitingBlocks.size() > 2)
+    return;
+
+  // Limit the CFG of the loop body for targets with a branch predictor.
+  // Allowing 4 blocks permits if-then-else diamonds in the body.
+  if (ST->hasBranchPredictor() && L->getNumBlocks() > 4)
     return;
 
   // Scan the loop: don't unroll loops with calls as this could prevent
   // inlining.
   unsigned Cost = 0;
-  for (auto &I : *BB) {
-    if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
-      ImmutableCallSite CS(&I);
-      if (const Function *F = CS.getCalledFunction()) {
-        if (!isLoweredToCall(F))
-          continue;
+  for (auto *BB : L->getBlocks()) {
+    for (auto &I : *BB) {
+      if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
+        ImmutableCallSite CS(&I);
+        if (const Function *F = CS.getCalledFunction()) {
+          if (!isLoweredToCall(F))
+            continue;
+        }
+        return;
       }
-      return;
+      SmallVector<const Value*, 4> Operands(I.value_op_begin(),
+                                            I.value_op_end());
+      Cost += getUserCost(&I, Operands);
     }
-    SmallVector<const Value*, 4> Operands(I.value_op_begin(),
-                                          I.value_op_end());
-    Cost += getUserCost(&I, Operands);
   }
 
+  DEBUG(dbgs() << "Cost of loop: " << Cost << "\n");
+
   UP.Partial = true;
   UP.Runtime = true;
   UP.UnrollRemainder = true;
Index: llvm/trunk/test/Transforms/LoopUnroll/ARM/multi-blocks.ll
===================================================================
--- llvm/trunk/test/Transforms/LoopUnroll/ARM/multi-blocks.ll
+++ llvm/trunk/test/Transforms/LoopUnroll/ARM/multi-blocks.ll
@@ -0,0 +1,316 @@
+; RUN: opt -mtriple=thumbv8m.main -mcpu=cortex-m33 -loop-unroll -S < %s -o - | FileCheck %s
+; RUN: opt -mtriple=thumbv7em -mcpu=cortex-m7 -loop-unroll -S < %s -o - | FileCheck %s
+
+;CHECK-LABEL: test_three_blocks
+;CHECK: for.body.epil:
+;CHECK: if.then.epil:
+;CHECK: for.inc.epil:
+;CHECK: for.body:
+;CHECK: if.then:
+;CHECK: for.inc:
+;CHECK: for.body.epil.1:
+;CHECK: if.then.epil.1:
+;CHECK: for.inc.epil.1:
+;CHECK: for.body.epil.2:
+;CHECK: if.then.epil.2:
+;CHECK: for.inc.epil.2:
+;CHECK: if.then.1:
+;CHECK: for.inc.1:
+;CHECK: if.then.2:
+;CHECK: for.inc.2:
+;CHECK: if.then.3:
+;CHECK: for.inc.3:
+define void @test_three_blocks(i32* nocapture %Output,
+                               i32* nocapture readonly %Condition,
+                               i32* nocapture readonly %Input,
+                               i32 %MaxJ) {
+entry:
+  %cmp8 = icmp eq i32 %MaxJ, 0
+  br i1 %cmp8, label %for.cond.cleanup, label %for.body.preheader
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.inc, %entry
+  %temp.0.lcssa = phi i32 [ 0, %entry ], [ %temp.1, %for.inc ]
+  store i32 %temp.0.lcssa, i32* %Output, align 4
+  ret void
+
+for.body:                                         ; preds = %for.body.preheader, %for.inc
+  %j.010 = phi i32 [ %inc, %for.inc ], [ 0, %for.body.preheader ]
+  %temp.09 = phi i32 [ %temp.1, %for.inc ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %Condition, i32 %j.010
+  %0 = load i32, i32* %arrayidx, align 4
+  %tobool = icmp eq i32 %0, 0
+  br i1 %tobool, label %for.inc, label %if.then
+
+if.then:                                          ; preds = %for.body
+  %arrayidx1 = getelementptr inbounds i32, i32* %Input, i32 %j.010
+  %1 = load i32, i32* %arrayidx1, align 4
+  %add = add i32 %1, %temp.09
+  br label %for.inc
+
+for.inc:                                          ; preds = %for.body, %if.then
+  %temp.1 = phi i32 [ %add, %if.then ], [ %temp.09, %for.body ]
+  %inc = add nuw i32 %j.010, 1
+  %exitcond = icmp eq i32 %inc, %MaxJ
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+}
+
+;CHECK-LABEL: test_two_exits
+;CHECK: for.body:
+;CHECK: if.end:
+;CHECK: cleanup.loopexit:
+;CHECK: cleanup:
+;CHECK: for.body.1:
+;CHECK: if.end.1:
+;CHECK: for.body.2:
+;CHECK: if.end.2:
+;CHECK: for.body.3:
+;CHECK: if.end.3:
+define void @test_two_exits(i32* nocapture %Output,
+                            i32* nocapture readonly %Condition,
+                            i32* nocapture readonly %Input,
+                            i32 %MaxJ) {
+entry:
+  %cmp14 = icmp eq i32 %MaxJ, 0
+  br i1 %cmp14, label %cleanup, label %for.body.preheader
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.preheader, %if.end
+  %j.016 = phi i32 [ %inc, %if.end ], [ 0, %for.body.preheader ]
+  %temp.015 = phi i32 [ %temp.0.add, %if.end ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %Input, i32 %j.016
+  %0 = load i32, i32* %arrayidx, align 4
+  %cmp1 = icmp ugt i32 %0, 65535
+  br i1 %cmp1, label %cleanup, label %if.end
+
+if.end:                                           ; preds = %for.body
+  %arrayidx2 = getelementptr inbounds i32, i32* %Condition, i32 %j.016
+  %1 = load i32, i32* %arrayidx2, align 4
+  %tobool = icmp eq i32 %1, 0
+  %add = select i1 %tobool, i32 0, i32 %0
+  %temp.0.add = add i32 %add, %temp.015
+  %inc = add nuw i32 %j.016, 1
+  %cmp = icmp ult i32 %inc, %MaxJ
+  br i1 %cmp, label %for.body, label %cleanup
+
+cleanup:                                          ; preds = %if.end, %for.body, %entry
+  %temp.0.lcssa = phi i32 [ 0, %entry ], [ %temp.015, %for.body ], [ %temp.0.add, %if.end ]
+  store i32 %temp.0.lcssa, i32* %Output, align 4
+  ret void
+}
+
+;CHECK-LABEL: test_three_exits
+;CHECK-NOT: for.body.epil
+;CHECK-NOT: if.end.epil
+;CHECK-LABEL: for.body
+;CHECK-LABEL: if.end
+;CHECK-LABEL: if.end5
+define void @test_three_exits(i32* nocapture %Output,
+                              i32* nocapture readonly %Condition,
+                              i32* nocapture readonly %Input,
+                              i32 %MaxJ) {
+entry:
+  %cmp20 = icmp eq i32 %MaxJ, 0
+  br i1 %cmp20, label %cleanup, label %for.body.preheader
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.preheader, %if.end5
+  %j.022 = phi i32 [ %inc, %if.end5 ], [ 0, %for.body.preheader ]
+  %temp.021 = phi i32 [ %temp.0.add, %if.end5 ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %Condition, i32 %j.022
+  %0 = load i32, i32* %arrayidx, align 4
+  %cmp1 = icmp ugt i32 %0, 65535
+  br i1 %cmp1, label %cleanup, label %if.end
+
+if.end:                                           ; preds = %for.body
+  %arrayidx2 = getelementptr inbounds i32, i32* %Input, i32 %j.022
+  %1 = load i32, i32* %arrayidx2, align 4
+  %cmp3 = icmp ugt i32 %1, 65535
+  br i1 %cmp3, label %cleanup, label %if.end5
+
+if.end5:                                          ; preds = %if.end
+  %tobool = icmp eq i32 %0, 0
+  %add = select i1 %tobool, i32 0, i32 %1
+  %temp.0.add = add i32 %add, %temp.021
+  %inc = add nuw i32 %j.022, 1
+  %cmp = icmp ult i32 %inc, %MaxJ
+  br i1 %cmp, label %for.body, label %cleanup
+
+cleanup:                                          ; preds = %if.end5, %for.body, %if.end, %entry
+  %temp.0.lcssa = phi i32 [ 0, %entry ], [ %temp.021, %if.end ], [ %temp.021, %for.body ], [ %temp.0.add, %if.end5 ]
+  store i32 %temp.0.lcssa, i32* %Output, align 4
+  ret void
+}
+
+;CHECK-LABEL: test_four_blocks
+;CHECK: for.body.epil:
+;CHECK: if.else.epil:
+;CHECK: if.then.epil:
+;CHECK: for.cond.cleanup:
+;CHECK: for.body:
+;CHECK: if.then:
+;CHECK: for.inc:
+;CHECK: for.body.epil.1:
+;CHECK: if.else.epil.1:
+;CHECK: if.then.epil.1:
+;CHECK: for.inc.epil.1:
+;CHECK: for.body.epil.2:
+;CHECK: if.else.epil.2:
+;CHECK: if.then.epil.2:
+;CHECK: for.inc.epil.2:
+;CHECK: if.else.1:
+;CHECK: if.then.1:
+;CHECK: for.inc.1:
+;CHECK: if.else.2:
+;CHECK: if.then.2:
+;CHECK: for.inc.2:
+;CHECK: if.else.3:
+;CHECK: if.then.3:
+;CHECK: for.inc.3:
+define void @test_four_blocks(i32* nocapture %Output,
+                              i32* nocapture readonly %Condition,
+                              i32* nocapture readonly %Input,
+                              i32 %MaxJ) {
+entry:
+  %cmp25 = icmp ugt i32 %MaxJ, 1
+  br i1 %cmp25, label %for.body.lr.ph, label %for.cond.cleanup
+
+for.body.lr.ph:                                   ; preds = %entry
+  %.pre = load i32, i32* %Input, align 4
+  br label %for.body
+
+for.cond.cleanup:                                 ; preds = %for.inc, %entry
+  %temp.0.lcssa = phi i32 [ 0, %entry ], [ %temp.1, %for.inc ]
+  store i32 %temp.0.lcssa, i32* %Output, align 4
+  ret void
+
+for.body:                                         ; preds = %for.inc, %for.body.lr.ph
+  %0 = phi i32 [ %.pre, %for.body.lr.ph ], [ %2, %for.inc ]
+  %j.027 = phi i32 [ 1, %for.body.lr.ph ], [ %inc, %for.inc ]
+  %temp.026 = phi i32 [ 0, %for.body.lr.ph ], [ %temp.1, %for.inc ]
+  %arrayidx = getelementptr inbounds i32, i32* %Condition, i32 %j.027
+  %1 = load i32, i32* %arrayidx, align 4
+  %cmp1 = icmp ugt i32 %1, 65535
+  %arrayidx2 = getelementptr inbounds i32, i32* %Input, i32 %j.027
+  %2 = load i32, i32* %arrayidx2, align 4
+  %cmp4 = icmp ugt i32 %2, %0
+  br i1 %cmp1, label %if.then, label %if.else
+
+if.then:                                          ; preds = %for.body
+  %cond = zext i1 %cmp4 to i32
+  %add = add i32 %temp.026, %cond
+  br label %for.inc
+
+if.else:                                          ; preds = %for.body
+  %not.cmp4 = xor i1 %cmp4, true
+  %sub = sext i1 %not.cmp4 to i32
+  %sub10.sink = add i32 %j.027, %sub
+  %arrayidx11 = getelementptr inbounds i32, i32* %Input, i32 %sub10.sink
+  %3 = load i32, i32* %arrayidx11, align 4
+  %sub13 = sub i32 %temp.026, %3
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then, %if.else
+  %temp.1 = phi i32 [ %add, %if.then ], [ %sub13, %if.else ]
+  %inc = add nuw i32 %j.027, 1
+  %exitcond = icmp eq i32 %inc, %MaxJ
+  br i1 %exitcond, label %for.cond.cleanup, label %for.body
+}
+
+;CHECK-LABEL: test_five_blocks
+;CHECK-NOT: for.body.epil:
+;CHECK: for.body:
+;CHECK: if.end:
+;CHECK: if.else:
+;CHECK: for.inc:
+;CHECK-NOT: for.inc.1:
+define void @test_five_blocks(i32* nocapture %Output,
+                              i32* nocapture readonly %Condition,
+                              i32* nocapture readonly %Input,
+                              i32 %MaxJ) {
+entry:
+  %cmp24 = icmp ugt i32 %MaxJ, 1
+  br i1 %cmp24, label %for.body.preheader, label %cleanup
+
+for.body.preheader:                               ; preds = %entry
+  br label %for.body
+
+for.body:                                         ; preds = %for.body.preheader, %for.inc
+  %j.026 = phi i32 [ %inc, %for.inc ], [ 1, %for.body.preheader ]
+  %temp.025 = phi i32 [ %temp.1, %for.inc ], [ 0, %for.body.preheader ]
+  %arrayidx = getelementptr inbounds i32, i32* %Input, i32 %j.026
+  %0 = load i32, i32* %arrayidx, align 4
+  %add = add i32 %0, %temp.025
+  %cmp1 = icmp ugt i32 %add, 16777215
+  br i1 %cmp1, label %cleanup, label %if.end
+
+if.end:                                           ; preds = %for.body
+  %arrayidx2 = getelementptr inbounds i32, i32* %Condition, i32 %j.026
+  %1 = load i32, i32* %arrayidx2, align 4
+  %cmp3 = icmp ugt i32 %1, 65535
+  br i1 %cmp3, label %if.then4, label %if.else
+
+if.then4:                                         ; preds = %if.end
+  %sub = add i32 %j.026, -1
+  %arrayidx6 = getelementptr inbounds i32, i32* %Input, i32 %sub
+  %2 = load i32, i32* %arrayidx6, align 4
+  %cmp7 = icmp ugt i32 %0, %2
+  %cond = zext i1 %cmp7 to i32
+  %add8 = add i32 %add, %cond
+  br label %for.inc
+
+if.else:                                          ; preds = %if.end
+  %and = and i32 %add, %0
+  br label %for.inc
+
+for.inc:                                          ; preds = %if.then4, %if.else
+  %temp.1 = phi i32 [ %add8, %if.then4 ], [ %and, %if.else ]
+  %inc = add nuw i32 %j.026, 1
+  %cmp = icmp ult i32 %inc, %MaxJ
+  br i1 %cmp, label %for.body, label %cleanup
+
+cleanup:                                          ; preds = %for.inc, %for.body, %entry
+  %temp.2 = phi i32 [ 0, %entry ], [ %add, %for.body ], [ %temp.1, %for.inc ]
+  store i32 %temp.2, i32* %Output, align 4
+  ret void
+}
+
+;CHECK-LABEL: iterate_inc
+;CHECK: while.body:
+;CHECK: while.end:
+;CHECK: while.body.1:
+;CHECK: while.body.2:
+;CHECK: while.body.3:
+%struct.Node = type { %struct.Node*, i32 }
+define void @iterate_inc(%struct.Node* %n, i32 %limit) {
+entry:
+  %tobool5 = icmp eq %struct.Node* %n, null
+  br i1 %tobool5, label %while.end, label %land.rhs.preheader
+
+land.rhs.preheader:                               ; preds = %entry
+  br label %land.rhs
+
+land.rhs:                                         ; preds = %land.rhs.preheader, %while.body
+  %list.addr.06 = phi %struct.Node* [ %2, %while.body ], [ %n, %land.rhs.preheader ]
+  %val = getelementptr inbounds %struct.Node, %struct.Node* %list.addr.06, i32 0, i32 1
+  %0 = load i32, i32* %val, align 4
+  %cmp = icmp slt i32 %0, %limit
+  br i1 %cmp, label %while.body, label %while.end
+
+while.body:                                       ; preds = %land.rhs
+  %inc = add nsw i32 %0, 1
+  store i32 %inc, i32* %val, align 4
+  %1 = bitcast %struct.Node* %list.addr.06 to %struct.Node**
+  %2 = load %struct.Node*, %struct.Node** %1, align 4
+  %tobool = icmp eq %struct.Node* %2, null
+  br i1 %tobool, label %while.end, label %land.rhs
+
+while.end:                                        ; preds = %land.rhs, %while.body, %entry
+  ret void
+}