diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
--- a/llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -106,6 +106,7 @@
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Scalar/GVNExpression.h"
+#include "llvm/Transforms/Utils/AssumeBundleBuilder.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/PredicateInfo.h"
 #include "llvm/Transforms/Utils/VNCoercion.h"
@@ -495,6 +496,7 @@
   AliasAnalysis *AA = nullptr;
   MemorySSA *MSSA = nullptr;
   MemorySSAWalker *MSSAWalker = nullptr;
+  AssumptionCache *AC = nullptr;
   const DataLayout &DL;
   std::unique_ptr<PredicateInfo> PredInfo;
 
@@ -658,7 +660,7 @@
   NewGVN(Function &F, DominatorTree *DT, AssumptionCache *AC,
          TargetLibraryInfo *TLI, AliasAnalysis *AA, MemorySSA *MSSA,
          const DataLayout &DL)
-      : F(F), DT(DT), TLI(TLI), AA(AA), MSSA(MSSA), DL(DL),
+      : F(F), DT(DT), TLI(TLI), AA(AA), MSSA(MSSA), AC(AC), DL(DL),
         PredInfo(std::make_unique<PredicateInfo>(F, *DT, *AC)),
         SQ(DL, TLI, DT, AC, /*CtxI=*/nullptr, /*UseInstrInfo=*/false) {}
 
@@ -3696,6 +3698,7 @@
       Inst.replaceAllUsesWith(UndefValue::get(Inst.getType()));
     if (isa<LandingPadInst>(Inst))
       continue;
+    salvageKnowledge(&Inst, AC);
 
     Inst.eraseFromParent();
     ++NumGVNInstrDeleted;
diff --git a/llvm/test/Transforms/NewGVN/2007-07-26-PhiErasure.ll b/llvm/test/Transforms/NewGVN/2007-07-26-PhiErasure.ll
--- a/llvm/test/Transforms/NewGVN/2007-07-26-PhiErasure.ll
+++ b/llvm/test/Transforms/NewGVN/2007-07-26-PhiErasure.ll
@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -newgvn -S | FileCheck %s
+; RUN: opt < %s -newgvn -S | FileCheck %s --check-prefixes=CHECK,NO_ASSUME
+; RUN: opt < %s -newgvn --enable-knowledge-retention -S | FileCheck %s --check-prefixes=CHECK,USE_ASSUME
 
 	%struct..0anon = type { i32 }
 	%struct.FILE = type { i8*, i32, i32, i16, i16, %struct.__sbuf, i32, i8*, i32 (i8*)*, i32 (i8*, i8*, i32)*, i64 (i8*, i64, i32)*, i32 (i8*, i8*, i32)*, %struct.__sbuf, %struct.__sFILEX*, i32, [3 x i8], [1 x i8], %struct.__sbuf, i32, i64 }
@@ -9,18 +10,32 @@
 @n_spills = external global i32		; <i32*> [#uses=2]
 
 define i32 @reload(%struct.rtx_def* %first, i32 %global, %struct.FILE* %dumpfile) {
-; CHECK-LABEL: @reload(
-; CHECK-NEXT:  cond_next2835.1:
-; CHECK-NEXT:    br label [[BB2928:%.*]]
-; CHECK:       bb2928:
-; CHECK-NEXT:    br i1 false, label [[COND_NEXT2943:%.*]], label [[COND_TRUE2935:%.*]]
-; CHECK:       cond_true2935:
-; CHECK-NEXT:    br label [[COND_NEXT2943]]
-; CHECK:       cond_next2943:
-; CHECK-NEXT:    br i1 false, label [[BB2982_PREHEADER:%.*]], label [[BB2928]]
-; CHECK:       bb2982.preheader:
-; CHECK-NEXT:    store i8 undef, i8* null
-; CHECK-NEXT:    ret i32 undef
+; NO_ASSUME-LABEL: @reload(
+; NO_ASSUME-NEXT:  cond_next2835.1:
+; NO_ASSUME-NEXT:    br label [[BB2928:%.*]]
+; NO_ASSUME:       bb2928:
+; NO_ASSUME-NEXT:    br i1 false, label [[COND_NEXT2943:%.*]], label [[COND_TRUE2935:%.*]]
+; NO_ASSUME:       cond_true2935:
+; NO_ASSUME-NEXT:    br label [[COND_NEXT2943]]
+; NO_ASSUME:       cond_next2943:
+; NO_ASSUME-NEXT:    br i1 false, label [[BB2982_PREHEADER:%.*]], label [[BB2928]]
+; NO_ASSUME:       bb2982.preheader:
+; NO_ASSUME-NEXT:    store i8 undef, i8* null
+; NO_ASSUME-NEXT:    ret i32 undef
+;
+; USE_ASSUME-LABEL: @reload(
+; USE_ASSUME-NEXT:  cond_next2835.1:
+; USE_ASSUME-NEXT:    br label [[BB2928:%.*]]
+; USE_ASSUME:       bb2928:
+; USE_ASSUME-NEXT:    br i1 false, label [[COND_NEXT2943:%.*]], label [[COND_TRUE2935:%.*]]
+; USE_ASSUME:       cond_true2935:
+; USE_ASSUME-NEXT:    br label [[COND_NEXT2943]]
+; USE_ASSUME:       cond_next2943:
+; USE_ASSUME-NEXT:    br i1 false, label [[BB2982_PREHEADER:%.*]], label [[BB2928]]
+; USE_ASSUME:       bb2982.preheader:
+; USE_ASSUME-NEXT:    call void @llvm.assume(i1 true) [ "align"(i32* @n_spills, i64 4), "dereferenceable"(i32* @n_spills, i64 4), "nonnull"(i32* @n_spills) ]
+; USE_ASSUME-NEXT:    store i8 undef, i8* null
+; USE_ASSUME-NEXT:    ret i32 undef
 ;
 cond_next2835.1:		; preds = %cond_next2861
   %tmp2922 = load i32, i32* @n_spills, align 4		; <i32> [#uses=0]