diff --git a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
--- a/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZFrameLowering.cpp
@@ -488,15 +488,6 @@
   MFFrame.setStackSize(StackSize);
 
   if (StackSize) {
-    // Determine if we want to store a backchain.
-    bool StoreBackchain = MF.getFunction().hasFnAttribute("backchain");
-
-    // If we need backchain, save current stack pointer.  R1 is free at this
-    // point.
-    if (StoreBackchain)
-      BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::LGR))
-        .addReg(SystemZ::R1D, RegState::Define).addReg(SystemZ::R15D);
-
     // Allocate StackSize bytes.
     int64_t Delta = -int64_t(StackSize);
     const unsigned ProbeSize = TLI.getStackProbeSize(MF);
@@ -512,18 +503,23 @@
         .addImm(StackSize);
     }
     else {
+      bool StoreBackchain = MF.getFunction().hasFnAttribute("backchain");
+      // If we need backchain, save current stack pointer.  R1 is free at
+      // this point.
+      if (StoreBackchain)
+        BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::LGR))
+          .addReg(SystemZ::R1D, RegState::Define).addReg(SystemZ::R15D);
       emitIncrement(MBB, MBBI, DL, SystemZ::R15D, Delta, ZII);
       buildCFAOffs(MBB, MBBI, DL, SPOffsetFromCFA + Delta, ZII);
+      if (StoreBackchain) {
+        // The back chain is stored topmost with packed-stack.
+        int Offset = usePackedStack(MF) ? SystemZMC::CallFrameSize - 8 : 0;
+        BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::STG))
+          .addReg(SystemZ::R1D, RegState::Kill).addReg(SystemZ::R15D)
+          .addImm(Offset).addReg(0);
+      }
     }
     SPOffsetFromCFA += Delta;
-
-    if (StoreBackchain) {
-      // The back chain is stored topmost with packed-stack.
-      int Offset = usePackedStack(MF) ? SystemZMC::CallFrameSize - 8 : 0;
-      BuildMI(MBB, MBBI, DL, ZII->get(SystemZ::STG))
-        .addReg(SystemZ::R1D, RegState::Kill).addReg(SystemZ::R15D)
-        .addImm(Offset).addReg(0);
-    }
   }
 
   if (HasFP) {
@@ -668,6 +664,13 @@
       .addMemOperand(MMO);
   };
 
+  bool StoreBackchain = MF.getFunction().hasFnAttribute("backchain");
+  if (StoreBackchain)
+    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::LGR))
+      .addReg(SystemZ::R1D, RegState::Define).addReg(SystemZ::R15D);
+
+  MachineBasicBlock *DoneMBB = nullptr;
+  MachineBasicBlock *LoopMBB = nullptr;
   if (NumFullBlocks < 3) {
     // Emit unrolled probe statements.
     for (unsigned int i = 0; i < NumFullBlocks; i++)
@@ -677,15 +680,16 @@
     uint64_t LoopAlloc = ProbeSize * NumFullBlocks;
     SPOffsetFromCFA -= LoopAlloc;
 
-    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::LGR), SystemZ::R1D)
+    // Use R0D to hold the exit value.
+    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::LGR), SystemZ::R0D)
       .addReg(SystemZ::R15D);
-    buildDefCFAReg(*MBB, MBBI, DL, SystemZ::R1D, ZII);
-    emitIncrement(*MBB, MBBI, DL, SystemZ::R1D, -int64_t(LoopAlloc), ZII);
+    buildDefCFAReg(*MBB, MBBI, DL, SystemZ::R0D, ZII);
+    emitIncrement(*MBB, MBBI, DL, SystemZ::R0D, -int64_t(LoopAlloc), ZII);
     buildCFAOffs(*MBB, MBBI, DL, -int64_t(SystemZMC::CallFrameSize + LoopAlloc),
                  ZII);
 
-    MachineBasicBlock *DoneMBB = SystemZ::splitBlockBefore(MBBI, MBB);
-    MachineBasicBlock *LoopMBB = SystemZ::emitBlockAfter(MBB);
+    DoneMBB = SystemZ::splitBlockBefore(MBBI, MBB);
+    LoopMBB = SystemZ::emitBlockAfter(MBB);
     MBB->addSuccessor(LoopMBB);
     LoopMBB->addSuccessor(LoopMBB);
     LoopMBB->addSuccessor(DoneMBB);
@@ -693,22 +697,32 @@
     MBB = LoopMBB;
     allocateAndProbe(*MBB, MBB->end(), ProbeSize, false/*EmitCFI*/);
     BuildMI(*MBB, MBB->end(), DL, ZII->get(SystemZ::CLGR))
-      .addReg(SystemZ::R15D).addReg(SystemZ::R1D);
+      .addReg(SystemZ::R15D).addReg(SystemZ::R0D);
     BuildMI(*MBB, MBB->end(), DL, ZII->get(SystemZ::BRC))
       .addImm(SystemZ::CCMASK_ICMP).addImm(SystemZ::CCMASK_CMP_GT).addMBB(MBB);
 
     MBB = DoneMBB;
     MBBI = DoneMBB->begin();
     buildDefCFAReg(*MBB, MBBI, DL, SystemZ::R15D, ZII);
-
-    recomputeLiveIns(*DoneMBB);
-    recomputeLiveIns(*LoopMBB);
   }
 
   if (Residual)
     allocateAndProbe(*MBB, MBBI, Residual, true/*EmitCFI*/);
 
+  if (StoreBackchain) {
+    // The back chain is stored topmost with packed-stack.
+    int Offset = usePackedStack(MF) ? SystemZMC::CallFrameSize - 8 : 0;
+    BuildMI(*MBB, MBBI, DL, ZII->get(SystemZ::STG))
+      .addReg(SystemZ::R1D, RegState::Kill).addReg(SystemZ::R15D)
+      .addImm(Offset).addReg(0);
+  }
+
   StackAllocMI->eraseFromParent();
+  if (DoneMBB != nullptr) {
+    // Compute the live-in lists for the new blocks.
+    recomputeLiveIns(*DoneMBB);
+    recomputeLiveIns(*LoopMBB);
+  }
 }
 
 bool SystemZFrameLowering::hasFP(const MachineFunction &MF) const {
diff --git a/llvm/test/CodeGen/SystemZ/stack-clash-dynamic-alloca.ll b/llvm/test/CodeGen/SystemZ/stack-clash-dynamic-alloca.ll
--- a/llvm/test/CodeGen/SystemZ/stack-clash-dynamic-alloca.ll
+++ b/llvm/test/CodeGen/SystemZ/stack-clash-dynamic-alloca.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14 | FileCheck %s
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14 -verify-machineinstrs | FileCheck %s
 
 define i32 @fun0(i32 %n) #0 {
 ; CHECK-LABEL: fun0:
@@ -92,14 +92,14 @@
 ; CHECK-NEXT:    stmg %r11, %r15, 88(%r15)
 ; CHECK-NEXT:    .cfi_offset %r11, -72
 ; CHECK-NEXT:    .cfi_offset %r15, -40
-; CHECK-NEXT:    lgr %r1, %r15
-; CHECK-NEXT:    .cfi_def_cfa_register %r1
-; CHECK-NEXT:    aghi %r1, -160
+; CHECK-NEXT:    lgr %r0, %r15
+; CHECK-NEXT:    .cfi_def_cfa_register %r0
+; CHECK-NEXT:    aghi %r0, -160
 ; CHECK-NEXT:    .cfi_def_cfa_offset 320
 ; CHECK-NEXT:  .LBB2_1: # =>This Inner Loop Header: Depth=1
 ; CHECK-NEXT:    aghi %r15, -8
 ; CHECK-NEXT:    cg %r0, 0(%r15)
-; CHECK-NEXT:    clgrjh %r15, %r1, .LBB2_1
+; CHECK-NEXT:    clgrjh %r15, %r0, .LBB2_1
 ; CHECK-NEXT:  # %bb.2:
 ; CHECK-NEXT:    .cfi_def_cfa_register %r15
 ; CHECK-NEXT:    lgr %r11, %r15
diff --git a/llvm/test/CodeGen/SystemZ/stack-clash-protection.ll b/llvm/test/CodeGen/SystemZ/stack-clash-protection.ll
--- a/llvm/test/CodeGen/SystemZ/stack-clash-protection.ll
+++ b/llvm/test/CodeGen/SystemZ/stack-clash-protection.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14 -O3 | FileCheck %s
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z14 -O3 -verify-machineinstrs | FileCheck %s
 ;
 ; Test stack clash protection probing for static allocas.
 
@@ -48,14 +48,14 @@
 define i32 @fun2() #0 {
 ; CHECK-LABEL: fun2:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    lgr %r1, %r15
-; CHECK-NEXT:    .cfi_def_cfa_register %r1
-; CHECK-NEXT:    agfi %r1, -69632
+; CHECK-NEXT:    lgr %r0, %r15
+; CHECK-NEXT:    .cfi_def_cfa_register %r0
+; CHECK-NEXT:    agfi %r0, -69632
 ; CHECK-NEXT:    .cfi_def_cfa_offset 69792
 ; CHECK-NEXT:  .LBB2_1: # =>This Inner Loop Header: Depth=1
 ; CHECK-NEXT:    aghi %r15, -4096
 ; CHECK-NEXT:    cg %r0, 4088(%r15)
-; CHECK-NEXT:    clgrjh %r15, %r1, .LBB2_1
+; CHECK-NEXT:    clgrjh %r15, %r0, .LBB2_1
 ; CHECK-NEXT:  # %bb.2:
 ; CHECK-NEXT:    .cfi_def_cfa_register %r15
 ; CHECK-NEXT:    aghi %r15, -2544
@@ -81,15 +81,15 @@
 define void @fun3() #0 {
 ; CHECK-LABEL: fun3:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    lgr %r1, %r15
-; CHECK-NEXT:    .cfi_def_cfa_register %r1
-; CHECK-NEXT:    aghi %r1, -28672
+; CHECK-NEXT:    lgr %r0, %r15
+; CHECK-NEXT:    .cfi_def_cfa_register %r0
+; CHECK-NEXT:    aghi %r0, -28672
 ; CHECK-NEXT:    .cfi_def_cfa_offset 28832
 ; CHECK-NEXT:  .LBB3_1: # %entry
 ; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
 ; CHECK-NEXT:    aghi %r15, -4096
 ; CHECK-NEXT:    cg %r0, 4088(%r15)
-; CHECK-NEXT:    clgrjh %r15, %r1, .LBB3_1
+; CHECK-NEXT:    clgrjh %r15, %r0, .LBB3_1
 ; CHECK-NEXT:  # %bb.2: # %entry
 ; CHECK-NEXT:    .cfi_def_cfa_register %r15
 ; CHECK-NEXT:    mvhi 180(%r15), 0
@@ -110,15 +110,15 @@
 define void @fun4() #0 "stack-probe-size"="8192" {
 ; CHECK-LABEL: fun4:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    lgr %r1, %r15
-; CHECK-NEXT:    .cfi_def_cfa_register %r1
-; CHECK-NEXT:    aghi %r1, -24576
+; CHECK-NEXT:    lgr %r0, %r15
+; CHECK-NEXT:    .cfi_def_cfa_register %r0
+; CHECK-NEXT:    aghi %r0, -24576
 ; CHECK-NEXT:    .cfi_def_cfa_offset 24736
 ; CHECK-NEXT:  .LBB4_1: # %entry
 ; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
 ; CHECK-NEXT:    aghi %r15, -8192
 ; CHECK-NEXT:    cg %r0, 8184(%r15)
-; CHECK-NEXT:    clgrjh %r15, %r1, .LBB4_1
+; CHECK-NEXT:    clgrjh %r15, %r0, .LBB4_1
 ; CHECK-NEXT:  # %bb.2: # %entry
 ; CHECK-NEXT:    .cfi_def_cfa_register %r15
 ; CHECK-NEXT:    aghi %r15, -7608
@@ -166,15 +166,15 @@
 define void @fun6() #0 "stack-probe-size"="5" {
 ; CHECK-LABEL: fun6:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    lgr %r1, %r15
-; CHECK-NEXT:    .cfi_def_cfa_register %r1
-; CHECK-NEXT:    aghi %r1, -4184
+; CHECK-NEXT:    lgr %r0, %r15
+; CHECK-NEXT:    .cfi_def_cfa_register %r0
+; CHECK-NEXT:    aghi %r0, -4184
 ; CHECK-NEXT:    .cfi_def_cfa_offset 4344
 ; CHECK-NEXT:  .LBB6_1: # %entry
 ; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
 ; CHECK-NEXT:    aghi %r15, -8
 ; CHECK-NEXT:    cg %r0, 0(%r15)
-; CHECK-NEXT:    clgrjh %r15, %r1, .LBB6_1
+; CHECK-NEXT:    clgrjh %r15, %r0, .LBB6_1
 ; CHECK-NEXT:  # %bb.2: # %entry
 ; CHECK-NEXT:    .cfi_def_cfa_register %r15
 ; CHECK-NEXT:    mvhi 180(%r15), 0
@@ -237,6 +237,37 @@
   ret i32 %c
 }
 
+define void @fun9() #0 "backchain" {
+; CHECK-LABEL: fun9:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    lgr %r1, %r15
+; CHECK-NEXT:    lgr %r0, %r15
+; CHECK-NEXT:    .cfi_def_cfa_register %r0
+; CHECK-NEXT:    aghi %r0, -28672
+; CHECK-NEXT:    .cfi_def_cfa_offset 28832
+; CHECK-NEXT:  .LBB9_1: # %entry
+; CHECK-NEXT:    # =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    aghi %r15, -4096
+; CHECK-NEXT:    cg %r0, 4088(%r15)
+; CHECK-NEXT:    clgrjh %r15, %r0, .LBB9_1
+; CHECK-NEXT:  # %bb.2: # %entry
+; CHECK-NEXT:    .cfi_def_cfa_register %r15
+; CHECK-NEXT:    stg %r1, 0(%r15)
+; CHECK-NEXT:    mvhi 180(%r15), 0
+; CHECK-NEXT:    l %r0, 180(%r15)
+; CHECK-NEXT:    aghi %r15, 28672
+; CHECK-NEXT:    br %r14
+entry:
+  %stack = alloca [7122 x i32], align 4
+  %i = alloca i32, align 4
+  %0 = bitcast [7122 x i32]* %stack to i8*
+  %i.0.i.0..sroa_cast = bitcast i32* %i to i8*
+  store volatile i32 0, i32* %i, align 4
+  %i.0.i.0.6 = load volatile i32, i32* %i, align 4
+  ret void
+}
+
+
 declare i32 @foo()
 attributes #0 = {  "probe-stack"="inline-asm"  }