Index: lib/Transforms/Scalar/LoopUnswitch.cpp
===================================================================
--- lib/Transforms/Scalar/LoopUnswitch.cpp
+++ lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -80,6 +80,7 @@
 
     struct LoopProperties {
       unsigned CanBeUnswitchedCount;
+      unsigned WasUnswitchedCount;
       unsigned SizeEstimation;
       UnswitchedValsMap UnswitchedVals;
     };
@@ -119,6 +120,10 @@
       // Check was this case value unswitched before or not.
       bool isUnswitched(const SwitchInst *SI, const Value *V);
 
+      // Returns true if another unswitching could be done within the cost
+      // threshold.
+      bool CostAllowsUnswitching();
+
       // Clone all loop-unswitch related loop properties.
       // Redistribute unswitching quotas.
       // Note, that new loop data is stored inside the VMap.
@@ -246,8 +251,9 @@
          I != E; ++I)
       Metrics.analyzeBasicBlock(*I, TTI, EphValues);
 
-    Props.SizeEstimation = std::min(Metrics.NumInsts, Metrics.NumBlocks * 5);
+    Props.SizeEstimation = Metrics.NumInsts;
     Props.CanBeUnswitchedCount = MaxSize / (Props.SizeEstimation);
+    Props.WasUnswitchedCount = 0;
     MaxSize -= Props.SizeEstimation * Props.CanBeUnswitchedCount;
 
     if (Metrics.notDuplicatable) {
@@ -258,13 +264,6 @@
     }
   }
 
-  if (!Props.CanBeUnswitchedCount) {
-    DEBUG(dbgs() << "NOT unswitching loop %"
-                 << L->getHeader()->getName() << ", cost too high: "
-                 << L->getBlocks().size() << "\n");
-    return false;
-  }
-
   // Be careful. This links are good only before new loop addition.
   CurrentLoopProperties = &Props;
   CurLoopInstructions = &Props.UnswitchedVals;
@@ -279,7 +278,8 @@
 
   if (LIt != LoopsProperties.end()) {
     LoopProperties &Props = LIt->second;
-    MaxSize += Props.CanBeUnswitchedCount * Props.SizeEstimation;
+    MaxSize += (Props.CanBeUnswitchedCount + Props.WasUnswitchedCount)
+      * Props.SizeEstimation;
     LoopsProperties.erase(LIt);
   }
 
@@ -299,6 +299,10 @@
   return (*CurLoopInstructions)[SI].count(V);
 }
 
+bool LUAnalysisCache::CostAllowsUnswitching() {
+  return CurrentLoopProperties->CanBeUnswitchedCount > 0;
+}
+
 // Clone all loop-unswitch related loop properties.
 // Redistribute unswitching quotas.
 // Note, that new loop data is stored inside the VMap.
@@ -312,6 +316,8 @@
   // Reallocate "can-be-unswitched quota"
 
   --OldLoopProps.CanBeUnswitchedCount;
+  ++OldLoopProps.WasUnswitchedCount;
+  NewLoopProps.WasUnswitchedCount = 0;
   unsigned Quota = OldLoopProps.CanBeUnswitchedCount;
   NewLoopProps.CanBeUnswitchedCount = Quota / 2;
   OldLoopProps.CanBeUnswitchedCount = Quota - Quota / 2;
@@ -656,6 +662,14 @@
   }
 
   // Check to see if it would be profitable to unswitch current loop.
+  if (!BranchesInfo.CostAllowsUnswitching()) {
+    DEBUG(dbgs() << "NOT unswitching loop %"
+                 << currentLoop->getHeader()->getName()
+                 << " at non-trivial condition '"
+                 << *Val << "' == " << *LoopCond << "\n"
+                 << ". Cost too high.\n");
+    return false;
+  }
 
   // Do not do non-trivial unswitch while optimizing for size.
   if (OptimizeForSize || F->hasFnAttribute(Attribute::OptimizeForSize))
Index: test/Transforms/LoopUnswitch/2015-06-10-Threshold.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopUnswitch/2015-06-10-Threshold.ll
@@ -0,0 +1,54 @@
+; RUN: opt < %s -loop-unswitch --loop-unswitch-threshold 4 \
+; RUN:   -verify-loop-info -S < %s 2>&1 -stats | FileCheck %s
+
+; Test for a bug. This tests that loop unswitching decisions in
+; different functions are independent. This was previously not the
+; case; the threshold of 4 would in effect be set to 0 after the first
+; unswitching and carried over as 0 into the next function.
+
+; CHECK-LABEL: @test1(
+define i32 @test1(i32* %var) {
+entry:
+; The loop should be unswitched on %c == true or %c == false, producing
+; two versions of the loop. The unswitch cost is 4.
+  %c = icmp eq i32 1, 2
+  br label %loop
+
+loop:
+  %i = phi i32 [0, %entry], [%nexti, %loop]
+  %incby = select i1 %c, i32 10, i32 20
+; CHECK-DAG: add i32 %i.us, 10
+; CHECK-DAG: add i32 %i, 20
+  %nexti = add i32 %i, %incby
+  %iterate = icmp eq i32 %nexti, 40
+  br i1 %iterate, label %loop, label %loop_exit
+
+; CHECK: loop_exit:
+loop_exit:
+  ret i32 0
+}
+
+; test2 is identical to test1, so the same thing should happen here as there.
+; CHECK-LABEL: @test2(
+define i32 @test2(i32* %var) {
+entry:
+  %c = icmp eq i32 1, 2
+  br label %loop
+
+loop:
+  %i = phi i32 [0, %entry], [%nexti, %loop]
+  %incby = select i1 %c, i32 10, i32 20
+; CHECK-DAG: add i32 %i.us, 10
+; CHECK-DAG: add i32 %i, 20
+  %nexti = add i32 %i, %incby
+  %iterate = icmp eq i32 %nexti, 40
+  br i1 %iterate, label %loop, label %loop_exit
+
+; CHECK: loop_exit:
+loop_exit:
+  ret i32 0
+}
+
+
+; CHECK: Statistics Collected
+; CHECK: 2 loop-unswitch - Number of selects unswitched
Index: test/Transforms/LoopUnswitch/2015-06-10-Trivial.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopUnswitch/2015-06-10-Trivial.ll
@@ -0,0 +1,68 @@
+; RUN: opt < %s -loop-unswitch --loop-unswitch-threshold 4 \
+; RUN:   -verify-loop-info -S < %s 2>&1 -stats | FileCheck %s
+
+; Test for a bug. This tests that trivial unswitching happens even if
+; the computed unswitching cost is above the threshold and that
+; unswitching other loops in the same function does not prevent
+; unswitching on trivial conditions.
+
+define i32 @test(i32* %var) {
+; CHECK-LABEL: @test(
+; The first loop should be unswitched trivially on %c1 == false, leaving
+; one version of the loop with %c1 == true and no version for %c1 == false.
+; The unswitch cost is 5, above the threshold, but that should not matter
+; for trivial unswitching.
+  %c1 = icmp eq i32 1, 1
+; CHECK: br i1 %c1
+  br label %loop1
+
+loop1:
+; CHECK-NOT: br i1 false
+; CHECK: br i1 true
+; CHECK-NOT: br i1 false
+  %dummy1 = add i32 1, 1  ; to make the unswitch cost 5
+  %dummy2 = add i32 1, 1
+  %dummy3 = add i32 1, 1
+  %dummy4 = add i32 1, 1
+  br i1 %c1, label %loop1, label %loop1_exit
+
+; CHECK: loop1_exit:
+loop1_exit:
+; The second loop should be unswitched non-trivially on %c2 == true or
+; %c2 == false, producing two versions of the loop. The unswitch cost is 4.
+  %c2 = icmp eq i32 1, 2
+  br label %loop2
+
+loop2:
+  %i = phi i32 [0, %loop1_exit], [%nexti, %loop2]
+  %incby = select i1 %c2, i32 10, i32 20
+; CHECK-DAG: add i32 %i.us, 10
+; CHECK-DAG: add i32 %i, 20
+  %nexti = add i32 %i, %incby
+  %iterate = icmp eq i32 %nexti, 40
+  br i1 %iterate, label %loop2, label %loop2_exit
+
+; CHECK: loop2_exit:
+loop2_exit:
+  %c3 = icmp eq i32 1, 1
+  br label %loop3
+
+; The third loop is trivially unswitchable like the first one, the only
+; difference is that the unswitchable condition is %c3 == true, not false.
+loop3:
+; CHECK-NOT: br i1 true
+; CHECK: br i1 false
+; CHECK-NOT: br i1 true
+  %dummy5 = add i32 1, 1  ; to make the unswitch cost 5
+  %dummy6 = add i32 1, 1
+  %dummy7 = add i32 1, 1
+  %dummy8 = add i32 1, 1
+  br i1 %c3, label %loop3_exit, label %loop3
+
+; CHECK: loop3_exit:
+loop3_exit:
+  ret i32 0
+}
+
+; CHECK: Statistics Collected
+; CHECK: 2 loop-unswitch - Number of unswitches that are trivial
\ No newline at end of file