From 98a0104014e9bb6ed89c2572f615351fd526674a Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 14 Aug 2009 20:48:13 +0000
Subject: [PATCH] Leaf functions which do not save CSRs can be frameless even
 with -disable-fp-elim.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79039 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMBaseRegisterInfo.cpp | 9 ++++++++-
 lib/Target/ARM/ARMBaseRegisterInfo.h   | 2 ++
 test/CodeGen/Thumb2/frameless.ll       | 6 ++++++
 3 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 test/CodeGen/Thumb2/frameless.ll

diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 309a5c6eb5d..12fbb5dc03e 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -440,6 +440,13 @@ bool ARMBaseRegisterInfo::hasFP(const MachineFunction &MF) const {
           MFI->isFrameAddressTaken());
 }
 
+bool ARMBaseRegisterInfo::hasStackFrame(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  if (NoFramePointerElim && MFI->hasCalls())
+    return true;
+  return MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken();
+}
+
 /// estimateStackSize - Estimate and return the size of the frame.
 static unsigned estimateStackSize(MachineFunction &MF, MachineFrameInfo *MFI) {
   const MachineFrameInfo *FFI = MF.getFrameInfo();
@@ -589,7 +596,7 @@ ARMBaseRegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
   }
 
   bool ExtraCSSpill = false;
-  if (!CanEliminateFrame || hasFP(MF)) {
+  if (!CanEliminateFrame || hasStackFrame(MF)) {
     AFI->setHasStackFrame(true);
 
     // If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.h b/lib/Target/ARM/ARMBaseRegisterInfo.h
index 92dbb8435d5..c242489fdb8 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.h
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.h
@@ -89,6 +89,8 @@ public:
 
   bool hasFP(const MachineFunction &MF) const;
 
+  bool hasStackFrame(const MachineFunction &MF) const;
+
   void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                             RegScavenger *RS = NULL) const;
 
diff --git a/test/CodeGen/Thumb2/frameless.ll b/test/CodeGen/Thumb2/frameless.ll
new file mode 100644
index 00000000000..1b6bb62d14e
--- /dev/null
+++ b/test/CodeGen/Thumb2/frameless.ll
@@ -0,0 +1,6 @@
+; RUN: llvm-as < %s | llc -mtriple=thumbv7-apple-darwin -disable-fp-elim | not grep mov
+; RUN: llvm-as < %s | llc -mtriple=thumbv7-linux -disable-fp-elim | not grep mov
+
+define arm_apcscc void @t() nounwind readnone {
+  ret void
+}