diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index cf3d16f05db..61966f52f51 100644
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2592,9 +2592,6 @@ void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
     LSRUse &LU = Uses[LUIdx];
     FormulaSorter Sorter(L, LU, SE, DT);
 
-    // Clear out the set of used regs; it will be recomputed.
-    LU.Regs.clear();
-
     for (size_t FIdx = 0, NumForms = LU.Formulae.size();
          FIdx != NumForms; ++FIdx) {
       Formula &F = LU.Formulae[FIdx];
@@ -2632,9 +2629,18 @@ void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
         --NumForms;
         continue;
       }
+    }
+
+    // Now that we've filtered out some formulae, recompute the Regs set.
+    LU.Regs.clear();
+    for (size_t FIdx = 0, NumForms = LU.Formulae.size();
+         FIdx != NumForms; ++FIdx) {
+      Formula &F = LU.Formulae[FIdx];
       if (F.ScaledReg) LU.Regs.insert(F.ScaledReg);
       LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
     }
+
+    // Reset this to prepare for the next use.
     BestFormulae.clear();
   }
 
@@ -2718,6 +2724,7 @@ void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
           LU.Formulae.pop_back();
           --e;
           --i;
+          assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
           continue;
         }
 
@@ -2810,6 +2817,7 @@ retry:
   // If none of the formulae had all of the required registers, relax the
   // constraint so that we don't exclude all formulae.
   if (!AnySatisfiedReqRegs) {
+    assert(!ReqRegs.empty() && "Solver failed even without required registers");
     ReqRegs.clear();
     goto retry;
   }
diff --git a/test/CodeGen/X86/lsr-delayed-fold.ll b/test/CodeGen/X86/lsr-delayed-fold.ll
index 17d6a4c0915..8afbb0d7a36 100644
--- a/test/CodeGen/X86/lsr-delayed-fold.ll
+++ b/test/CodeGen/X86/lsr-delayed-fold.ll
@@ -49,3 +49,86 @@ lbl_264:                                          ; preds = %if.end, %lbl_264.pr
   %tobool12 = icmp eq i8 %mul.i18, 0              ; <i1> [#uses=1]
   unreachable
 }
+
+; LSR ends up going into conservative pruning mode; don't prune the solution
+; so far that it becomes unsolvable though.
+; PR7077
+
+%struct.Bu = type { i32, i32, i32 }
+
+define void @_Z3fooP2Bui(%struct.Bu* nocapture %bu) {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.inc131, %entry
+  %indvar = phi i64 [ %indvar.next, %for.inc131 ], [ 0, %entry ] ; <i64> [#uses=3]
+  br i1 undef, label %for.inc131, label %lor.lhs.false
+
+lor.lhs.false:                                    ; preds = %for.body
+  %tmp15 = add i64 %indvar, 1                     ; <i64> [#uses=1]
+  %tmp17 = add i64 %indvar, 2                      ; <i64> [#uses=1]
+  %tmp19 = add i64 %indvar, 3                      ; <i64> [#uses=1]
+  %tmp21 = add i64 %indvar, 4                      ; <i64> [#uses=1]
+  %tmp23 = add i64 %indvar, 5                      ; <i64> [#uses=1]
+  %tmp25 = add i64 %indvar, 6                      ; <i64> [#uses=1]
+  %tmp27 = add i64 %indvar, 7                      ; <i64> [#uses=1]
+  %tmp29 = add i64 %indvar, 8                      ; <i64> [#uses=1]
+  %tmp31 = add i64 %indvar, 9                      ; <i64> [#uses=1]
+  %tmp35 = add i64 %indvar, 11                     ; <i64> [#uses=1]
+  %tmp37 = add i64 %indvar, 12                     ; <i64> [#uses=1]
+  %tmp39 = add i64 %indvar, 13                     ; <i64> [#uses=1]
+  %tmp41 = add i64 %indvar, 14                     ; <i64> [#uses=1]
+  %tmp43 = add i64 %indvar, 15                     ; <i64> [#uses=1]
+  %tmp45 = add i64 %indvar, 16                     ; <i64> [#uses=1]
+  %tmp47 = add i64 %indvar, 17                     ; <i64> [#uses=1]
+  %mul = trunc i64 %indvar to i32                  ; <i32> [#uses=1]
+  %add22 = trunc i64 %tmp15 to i32                ; <i32> [#uses=1]
+  %add28 = trunc i64 %tmp17 to i32                ; <i32> [#uses=1]
+  %add34 = trunc i64 %tmp19 to i32                ; <i32> [#uses=1]
+  %add40 = trunc i64 %tmp21 to i32                ; <i32> [#uses=1]
+  %add46 = trunc i64 %tmp23 to i32                ; <i32> [#uses=1]
+  %add52 = trunc i64 %tmp25 to i32                ; <i32> [#uses=1]
+  %add58 = trunc i64 %tmp27 to i32                ; <i32> [#uses=1]
+  %add64 = trunc i64 %tmp29 to i32                ; <i32> [#uses=1]
+  %add70 = trunc i64 %tmp31 to i32                ; <i32> [#uses=1]
+  %add82 = trunc i64 %tmp35 to i32                ; <i32> [#uses=1]
+  %add88 = trunc i64 %tmp37 to i32                ; <i32> [#uses=1]
+  %add94 = trunc i64 %tmp39 to i32                ; <i32> [#uses=1]
+  %add100 = trunc i64 %tmp41 to i32               ; <i32> [#uses=1]
+  %add106 = trunc i64 %tmp43 to i32               ; <i32> [#uses=1]
+  %add112 = trunc i64 %tmp45 to i32               ; <i32> [#uses=1]
+  %add118 = trunc i64 %tmp47 to i32               ; <i32> [#uses=1]
+  %tmp10 = getelementptr %struct.Bu* %bu, i64 %indvar, i32 2 ; <i32*> [#uses=1]
+  %tmp11 = load i32* %tmp10                       ; <i32> [#uses=0]
+  tail call void undef(i32 %add22)
+  tail call void undef(i32 %add28)
+  tail call void undef(i32 %add34)
+  tail call void undef(i32 %add40)
+  tail call void undef(i32 %add46)
+  tail call void undef(i32 %add52)
+  tail call void undef(i32 %add58)
+  tail call void undef(i32 %add64)
+  tail call void undef(i32 %add70)
+  tail call void undef(i32 %add82)
+  tail call void undef(i32 %add88)
+  tail call void undef(i32 %add94)
+  tail call void undef(i32 %add100)
+  tail call void undef(i32 %add106)
+  tail call void undef(i32 %add112)
+  tail call void undef(i32 %add118)
+  br label %for.body123
+
+for.body123:                                      ; preds = %for.body123, %lor.lhs.false
+  %j.03 = phi i32 [ 0, %lor.lhs.false ], [ %inc, %for.body123 ] ; <i32> [#uses=2]
+  %add129 = add i32 %mul, %j.03                   ; <i32> [#uses=1]
+  tail call void undef(i32 %add129)
+  %inc = add nsw i32 %j.03, 1                     ; <i32> [#uses=1]
+  br i1 undef, label %for.inc131, label %for.body123
+
+for.inc131:                                       ; preds = %for.body123, %for.body
+  %indvar.next = add i64 %indvar, 1               ; <i64> [#uses=1]
+  br i1 undef, label %for.end134, label %for.body
+
+for.end134:                                       ; preds = %for.inc131
+  ret void
+}