From 5c57639c283479a7b1c66e27a745d31b310291c4 Mon Sep 17 00:00:00 2001
From: Jim Grosbach <grosbach@apple.com>
Date: Mon, 18 Oct 2010 18:39:46 +0000
Subject: [PATCH] For Thumb2, try to use frame pointer references for stack
 slots even when a base register is available. rdar://8525298

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116729 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMBaseRegisterInfo.cpp | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index acb61b218ac..37e15f4f1c1 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -953,8 +953,16 @@ ARMBaseRegisterInfo::ResolveFrameIndexReference(const MachineFunction &MF,
       return FPOffset;
     } else if (MFI->hasVarSizedObjects()) {
       assert(hasBasePointer(MF) && "missing base pointer!");
-      // Use the base register since we have it.
-      FrameReg = BasePtr;
+      // Try to use the frame pointer if we can, else use the base pointer
+      // since it's available. This is handy for the emergency spill slot, in
+      // particular.
+      if (AFI->isThumb2Function()) {
+        if (FPOffset >= -255 && FPOffset < 0) {
+          FrameReg = getFrameRegister(MF);
+          return FPOffset;
+        }
+      } else
+        FrameReg = BasePtr;
     } else if (AFI->isThumb2Function()) {
       // In Thumb2 mode, the negative offset is very limited. Try to avoid
       // out of range references.