Index: llvm/lib/Transforms/IPO/Attributor.cpp
===================================================================
--- llvm/lib/Transforms/IPO/Attributor.cpp
+++ llvm/lib/Transforms/IPO/Attributor.cpp
@@ -1995,14 +1995,21 @@
       assert(PtrOp &&
              "Expected pointer operand of memory accessing instruction");
 
+      // Either we stopped and the appropriate action was taken,
+      // or we got back a simplified value to continue.
+      Optional<Value *> SimplifiedPtrOp = stopOnUndefOrAssumed(A, PtrOp, &I);
+      if (!SimplifiedPtrOp.hasValue())
+        return true;
+      const Value *PtrOpVal = SimplifiedPtrOp.getValue();
+
       // A memory access through a pointer is considered UB
       // only if the pointer has constant null value.
       // TODO: Expand it to not only check constant values.
-      if (!isa<ConstantPointerNull>(PtrOp)) {
+      if (!isa<ConstantPointerNull>(PtrOpVal)) {
         AssumedNoUBInsts.insert(&I);
         return true;
       }
-      const Type *PtrTy = PtrOp->getType();
+      const Type *PtrTy = PtrOpVal->getType();
 
       // Because we only consider instructions inside functions,
       // assume that a parent function exists.
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/2008-02-01-ReturnAttrs.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/2008-02-01-ReturnAttrs.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/2008-02-01-ReturnAttrs.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 -S < %s | FileCheck %s
+; RUN: opt -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=3 -S < %s | FileCheck %s
 
 define internal i32 @deref(i32* %x) nounwind {
 ; CHECK-LABEL: define {{[^@]+}}@deref
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/2008-07-02-array-indexing.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/2008-07-02-array-indexing.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/2008-07-02-array-indexing.ll
@@ -8,8 +8,7 @@
 ; CHECK-LABEL: define {{[^@]+}}@callee
 ; CHECK-SAME: (i1 [[C:%.*]], i32* noalias nocapture nofree nonnull readonly dereferenceable(4) [[A:%.*]])
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[A_0:%.*]] = load i32, i32* null
-; CHECK-NEXT:    br i1 false, label [[T:%.*]], label [[F:%.*]]
+; CHECK-NEXT:    unreachable
 ; CHECK:       T:
 ; CHECK-NEXT:    unreachable
 ; CHECK:       F:
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/X86/attributes.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/X86/attributes.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/X86/attributes.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s
+; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=3 < %s | FileCheck %s
 ; Test that we only promote arguments when the caller/callee have compatible
 ; function attrubtes.
 
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/X86/min-legal-vector-width.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/X86/min-legal-vector-width.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/X86/min-legal-vector-width.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s
+; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=3 < %s | FileCheck %s
 ; Test that we only promote arguments when the caller/callee have compatible
 ; function attrubtes.
 
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/fp80.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/fp80.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/fp80.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s
+; RUN: opt -S -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=3 < %s | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/inalloca.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/inalloca.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/inalloca.ll
@@ -1,6 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
 ; RUN: opt -S -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s --check-prefixes=ATTRIBUTOR
-; RUN: opt -S -passes='globalopt,attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s --check-prefixes=GLOBALOPT_ATTRIBUTOR
+; RUN: opt -S -passes='globalopt,attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=4 < %s | FileCheck %s --check-prefixes=GLOBALOPT_ATTRIBUTOR
 
 target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
 
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/profile.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/profile.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/profile.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s
+; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=3 < %s | FileCheck %s
 target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-v64:64:64-v128:128:128"
 
 ; Checks if !prof metadata is corret in deadargelim.
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/reserve-tbaa.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/reserve-tbaa.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/reserve-tbaa.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s
+; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=3 < %s | FileCheck %s
 
 ; PR17906
 ; When we promote two arguments in a single function with different types,
Index: llvm/test/Transforms/Attributor/ArgumentPromotion/sret.ll
===================================================================
--- llvm/test/Transforms/Attributor/ArgumentPromotion/sret.ll
+++ llvm/test/Transforms/Attributor/ArgumentPromotion/sret.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s
+; RUN: opt -S -passes='attributor' -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=4 < %s | FileCheck %s
 
 target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-pc-windows-msvc"
Index: llvm/test/Transforms/Attributor/IPConstantProp/2009-09-24-byval-ptr.ll
===================================================================
--- llvm/test/Transforms/Attributor/IPConstantProp/2009-09-24-byval-ptr.ll
+++ llvm/test/Transforms/Attributor/IPConstantProp/2009-09-24-byval-ptr.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
-; RUN: opt -S -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=2 < %s | FileCheck %s
+; RUN: opt -S -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-max-iterations=3 < %s | FileCheck %s
 ; Don't constant-propagate byval pointers, since they are not pointers!
 ; PR5038
 %struct.MYstr = type { i8, i32 }
Index: llvm/test/Transforms/Attributor/IPConstantProp/PR26044.ll
===================================================================
--- llvm/test/Transforms/Attributor/IPConstantProp/PR26044.ll
+++ llvm/test/Transforms/Attributor/IPConstantProp/PR26044.ll
@@ -11,7 +11,7 @@
 ; CHECK:       for.cond1:
 ; CHECK-NEXT:    unreachable
 ; CHECK:       if.end:
-; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* undef, align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* null, align 4
 ; CHECK-NEXT:    [[CALL:%.*]] = call i32 @fn1(i32 [[TMP0]])
 ; CHECK-NEXT:    store i32 [[CALL]], i32* [[P]]
 ; CHECK-NEXT:    br label %for.cond1
@@ -52,7 +52,7 @@
 ; CHECK:       for.cond1:
 ; CHECK-NEXT:    unreachable
 ; CHECK:       if.end:
-; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* undef, align 4
+; CHECK-NEXT:    [[TMP0:%.*]] = load i32, i32* null, align 4
 ; CHECK-NEXT:    [[CALL:%.*]] = call i32 @fn0(i32 [[TMP0]])
 ; CHECK-NEXT:    store i32 [[CALL]], i32* [[P]]
 ; CHECK-NEXT:    br label %for.cond1
Index: llvm/test/Transforms/Attributor/align.ll
===================================================================
--- llvm/test/Transforms/Attributor/align.ll
+++ llvm/test/Transforms/Attributor/align.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 
Index: llvm/test/Transforms/Attributor/internal-noalias.ll
===================================================================
--- llvm/test/Transforms/Attributor/internal-noalias.ll
+++ llvm/test/Transforms/Attributor/internal-noalias.ll
@@ -1,4 +1,4 @@
-; RUN: opt -S -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=5 < %s | FileCheck %s
+; RUN: opt -S -passes=attributor -aa-pipeline='basic-aa' -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=6 < %s | FileCheck %s
 
 define dso_local i32 @visible(i32* noalias %A, i32* noalias %B) #0 {
 entry:
Index: llvm/test/Transforms/Attributor/returned.ll
===================================================================
--- llvm/test/Transforms/Attributor/returned.ll
+++ llvm/test/Transforms/Attributor/returned.ll
@@ -1,4 +1,4 @@
-; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=5 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
+; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-max-iterations-verify -attributor-annotate-decl-cs -attributor-max-iterations=6 -S < %s | FileCheck %s --check-prefix=ATTRIBUTOR
 ; RUN: opt -attributor -attributor-manifest-internal -attributor-disable=false -attributor-annotate-decl-cs -functionattrs -S < %s | FileCheck %s --check-prefix=BOTH
 ;
 ; Copied from Transforms/FunctoinAttrs/read_write_returned_arguments_scc.ll