commit 1825fac3c914ad555f87e8995cdb7d92c33fb55e
author Saleem Abdulrasool <compnerd@compnerd.org> Fri Oct 09 03:19:03 2015 +0000
committer Saleem Abdulrasool <compnerd@compnerd.org> Fri Oct 09 03:19:03 2015 +0000
tree 6bd78b37c6b2c97d52ab47ba2f0bb61efca32d89
parent fe7eeed585da351c3dddfd7fead6b0311595cc4d

ARM: tweak WoA frame lowering

Accept r11 when targeting Windows on ARM rather than just low registers.
Because we are in a thumb-2 only mode, this may be slightly more expensive in
code size, but results in better code for the environment since it spills the
frame register, which is generally desired for fast stack walking as per the
ABI.

llvm-svn: 249804

llvm/lib/Target/ARM/ARMFrameLowering.cpp

diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
index 476a12f..802946a 100644
--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
@@ -1605,13 +1605,11 @@
   // FIXME: We could add logic to be more precise about negative offsets
   //        and which instructions will need a scratch register for them. Is it
   //        worth the effort and added fragility?
-  bool BigStack =
-    (RS &&
-     (MFI->estimateStackSize(MF) +
-      ((hasFP(MF) && AFI->hasStackFrame()) ? 4:0) >=
-      estimateRSStackSizeLimit(MF, this)))
-    || MFI->hasVarSizedObjects()
-    || (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF));
+  bool BigStack = (RS && (MFI->estimateStackSize(MF) +
+                              ((hasFP(MF) && AFI->hasStackFrame()) ? 4 : 0) >=
+                          estimateRSStackSizeLimit(MF, this))) ||
+                  MFI->hasVarSizedObjects() ||
+                  (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF));
 
   bool ExtraCSSpill = false;
   if (BigStack || !CanEliminateFrame || RegInfo->cannotEliminateFrame(MF)) {
@@ -1649,8 +1647,10 @@
       if (CS1Spilled && !UnspilledCS1GPRs.empty()) {
         for (unsigned i = 0, e = UnspilledCS1GPRs.size(); i != e; ++i) {
           unsigned Reg = UnspilledCS1GPRs[i];
-          // Don't spill high register if the function is thumb
+          // Don't spill high register if the function is thumb.  In the case of
+          // Windows on ARM, accept R11 (frame pointer)
           if (!AFI->isThumbFunction() ||
+              (STI.isTargetWindows() && Reg == ARM::R11) ||
               isARMLowRegister(Reg) || Reg == ARM::LR) {
             SavedRegs.set(Reg);
             if (!MRI.isReserved(Reg))