Index: llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
===================================================================
--- llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
+++ llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
@@ -350,6 +350,14 @@
     assert(MFI.isObjectPreAllocated(FrameIdx) &&
            "Only pre-allocated locals expected!");
 
+    // We need to keep the references to the stack protector slot through frame
+    // index operands so that it gets resolved by PEI rather than this pass.
+    // This avoids accesses to the stack protector though virtual base
+    // registers, and forces PEI to address it using fp/sp/bp.
+    if (MFI.hasStackProtectorIndex() &&
+        FrameIdx == MFI.getStackProtectorIndex())
+      continue;
+
     LLVM_DEBUG(dbgs() << "Considering: " << MI);
 
     unsigned idx = 0;
Index: llvm/test/CodeGen/Thumb/stack_guard_remat.ll
===================================================================
--- llvm/test/CodeGen/Thumb/stack_guard_remat.ll
+++ llvm/test/CodeGen/Thumb/stack_guard_remat.ll
@@ -3,6 +3,7 @@
 ; RUN: llc < %s -mtriple=thumb-apple-darwin -relocation-model=dynamic-no-pic -no-integrated-as | FileCheck %s  -check-prefix=NO-PIC -check-prefix=DYNAMIC-NO-PIC
 
 ;PIC:   foo2
+;PIC:   ldr {{r[0-9]+}}, {{LCPI[0-9_]+}}
 ;PIC:   ldr [[R0:r[0-9]+]], [[LABEL0:LCPI[0-9_]+]]
 ;PIC: [[LABEL1:LPC[0-9_]+]]:
 ;PIC:   add [[R0]], pc
@@ -13,6 +14,7 @@
 ;PIC-NEXT:   .long L___stack_chk_guard$non_lazy_ptr-([[LABEL1]]+4)
 
 ;NO-PIC:   foo2
+;NO-PIC:   ldr {{r[0-9]+}}, {{LCPI[0-9_]+}}
 ;NO-PIC:   ldr [[R0:r[0-9]+]], [[LABEL0:LCPI[0-9_]+]]
 ;NO-PIC-NOT: LPC
 ;NO-PIC:   ldr {{r[0-9]+}}, {{\[}}[[R0]]{{\]}}
Index: test/CodeGen/AArch64/stack-protector-frame-index.mir
===================================================================
--- /dev/null
+++ test/CodeGen/AArch64/stack-protector-frame-index.mir
@@ -0,0 +1,27 @@
+# RUN: llc -mtriple=arm64-apple-ios -run-pass=localstackalloc -o - %s | FileCheck %s
+# Check that the pass doesn't re-write stack protector accesses using a virtual
+# base register.
+
+# RUN: llc -mtriple=arm64-apple-ios -start-before=localstackalloc -stop-after=prologepilog -o - %s | FileCheck %s --check-prefix=CHECK-PEI
+# Check that PEI handles the re-write and uses x29 as a base reg.
+
+---
+name:            main
+tracksRegLiveness: true
+frameInfo:
+  stackProtector:  '%stack.0'
+stack:
+  - { id: 0, size: 8, alignment: 8, stack-id: 0 }
+body:             |
+  bb.0:
+
+    %0:gpr64common = IMPLICIT_DEF
+    STRXui killed %0, %stack.0, 0 :: (volatile store 8 into %stack.0)
+    %1:gpr64 = LDRXui %stack.0, 0 :: (volatile load 8 from %stack.0)
+    ; CHECK:      STRXui killed %0, %stack.0, 0 :: (volatile store 8 into %stack.0)
+    ; CHECK-NEXT: %1:gpr64 = LDRXui %stack.0, 0 :: (volatile load 8 from %stack.0)
+    ; CHECK-PEI:      STRXui undef renamable $[[REG:x[0-9]+]], $sp, 1 :: (volatile store 8 into %stack.0)
+    ; CHECK-PEI-NEXT: dead renamable $[[REG]] = LDRXui $sp, 1 :: (volatile load 8 from %stack.0)
+    RET_ReallyLR implicit undef $w0
+
+...