diff --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -1710,13 +1710,6 @@
   if (!MaybeImmVal)
     return false;
 
-  // Don't do this combine if there multiple uses of the first PTR_ADD,
-  // since we may be able to compute the second PTR_ADD as an immediate
-  // offset anyway. Folding the first offset into the second may cause us
-  // to go beyond the bounds of our legal addressing modes.
-  if (!MRI.hasOneNonDBGUse(Add2))
-    return false;
-
   MachineInstr *Add2Def = MRI.getUniqueVRegDef(Add2);
   if (!Add2Def || Add2Def->getOpcode() != TargetOpcode::G_PTR_ADD)
     return false;
@@ -1727,8 +1720,36 @@
   if (!MaybeImm2Val)
     return false;
 
+  // Check if the new combined immediate forms an illegal addressing mode.
+  // Do not combine if it was legal before but would get illegal.
+  // To do so, we need to find a load/store user of the pointer to get
+  // the access type.
+  Type *AccessTy = nullptr;
+  auto &MF = *MI.getMF();
+  for (auto &UseMI : MRI.use_nodbg_instructions(MI.getOperand(0).getReg())) {
+    if (auto *LdSt = dyn_cast<GLoadStore>(&UseMI)) {
+      AccessTy = getTypeForLLT(MRI.getType(LdSt->getReg(0)),
+                               MF.getFunction().getContext());
+      break;
+    }
+  }
+  TargetLoweringBase::AddrMode AMNew;
+  APInt CombinedImm = MaybeImmVal->Value + MaybeImm2Val->Value;
+  AMNew.BaseOffs = CombinedImm.getSExtValue();
+  if (AccessTy) {
+    AMNew.HasBaseReg = true;
+    TargetLoweringBase::AddrMode AMOld;
+    AMOld.BaseOffs = MaybeImm2Val->Value.getSExtValue();
+    AMOld.HasBaseReg = true;
+    unsigned AS = MRI.getType(Add2).getAddressSpace();
+    const auto &TLI = *MF.getSubtarget().getTargetLowering();
+    if (TLI.isLegalAddressingMode(MF.getDataLayout(), AMOld, AccessTy, AS) &&
+        !TLI.isLegalAddressingMode(MF.getDataLayout(), AMNew, AccessTy, AS))
+      return false;
+  }
+
   // Pass the combined immediate to the apply function.
-  MatchInfo.Imm = (MaybeImmVal->Value + MaybeImm2Val->Value).getSExtValue();
+  MatchInfo.Imm = AMNew.BaseOffs;
   MatchInfo.Base = Base;
   return true;
 }
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-reassociation.mir b/llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-reassociation.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-reassociation.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/combine-ptradd-reassociation.mir
@@ -13,7 +13,7 @@
     ; CHECK-LABEL: name: test1_noreassoc_legal_already_new_is_illegal
     ; CHECK: liveins: $x0
     ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
-    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 4777
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 1600
     ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 6
     ; CHECK: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
     ; CHECK: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C]](s64)
@@ -23,7 +23,7 @@
     ; CHECK: $w0 = COPY [[LOAD]](s32)
     ; CHECK: RET_ReallyLR implicit $w0
     %0:_(p0) = COPY $x0
-    %2:_(s64) = G_CONSTANT i64 4777
+    %2:_(s64) = G_CONSTANT i64 1600
     %4:_(s64) = G_CONSTANT i64 6
     %9:_(s32) = G_CONSTANT i32 0
     %10:_(p0) = G_PTR_ADD %0, %2(s64)
@@ -161,7 +161,7 @@
     ; CHECK-LABEL: name: walk_through_inttoptr
     ; CHECK: liveins: $x0
     ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
-    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 4777
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 1600
     ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 6
     ; CHECK: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
     ; CHECK: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C]](s64)
@@ -173,7 +173,7 @@
     ; CHECK: $w0 = COPY [[LOAD]](s32)
     ; CHECK: RET_ReallyLR implicit $w0
     %0:_(p0) = COPY $x0
-    %2:_(s64) = G_CONSTANT i64 4777
+    %2:_(s64) = G_CONSTANT i64 1600
     %4:_(s64) = G_CONSTANT i64 6
     %9:_(s32) = G_CONSTANT i32 0
     %10:_(p0) = G_PTR_ADD %0, %2(s64)
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-ptradd-chain.mir b/llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-ptradd-chain.mir
--- a/llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-ptradd-chain.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/prelegalizercombiner-ptradd-chain.mir
@@ -1,5 +1,6 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
-# RUN: llc -mtriple aarch64-apple-ios  -run-pass=aarch64-prelegalizer-combiner %s -o - -verify-machineinstrs | FileCheck %s
+# RUN: llc -mtriple aarch64-apple-ios  -run-pass=aarch64-prelegalizer-combiner --aarch64prelegalizercombinerhelper-only-enable-rule="ptr_add_immed_chain"  %s -o - -verify-machineinstrs | FileCheck %s
+# REQUIRES: asserts
 
 # Check that we fold two adds of constant offsets with G_PTR_ADD into a single G_PTR_ADD.
 ---
@@ -70,3 +71,33 @@
     $x0 = COPY %5(p0)
     RET_ReallyLR implicit $x0
 ...
+---
+name: ptradd_would_form_illegal_load_addressing
+tracksRegLiveness: true
+body:             |
+  bb.1:
+    liveins: $x0
+
+    ; CHECK-LABEL: name: ptradd_would_form_illegal_load_addressing
+    ; CHECK: liveins: $x0
+    ; CHECK: [[COPY:%[0-9]+]]:_(p0) = COPY $x0
+    ; CHECK: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 4
+    ; CHECK: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 4096
+    ; CHECK: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[COPY]], [[C]](s64)
+    ; CHECK: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[PTR_ADD]], [[C1]](s64)
+    ; CHECK: %ld:_(s64) = G_LOAD [[PTR_ADD1]](p0) :: (load (s64))
+    ; CHECK: %ld_other:_(s64) = G_LOAD [[PTR_ADD]](p0) :: (load (s64))
+    ; CHECK: $x0 = COPY %ld(s64)
+    ; CHECK: $x1 = COPY %ld_other(s64)
+    ; CHECK: RET_ReallyLR implicit $x0
+    %0:_(p0) = COPY $x0
+    %1:_(s64) = G_CONSTANT i64 4
+    %2:_(s64) = G_CONSTANT i64 4096
+    %3:_(p0) = G_PTR_ADD %0(p0), %1
+    %4:_(p0) = G_PTR_ADD %3(p0), %2
+    %ld:_(s64) = G_LOAD %4(p0) :: (load 8)
+    %ld_other:_(s64) = G_LOAD %3(p0) :: (load 8)
+    $x0 = COPY %ld(s64)
+    $x1 = COPY %ld_other(s64)
+    RET_ReallyLR implicit $x0
+...