Restore the behavior of frame lowering before my refactoring.

It turns out that ppc backend has really weird interdependencies
over different hooks and all stuff is fragile wrt small changes.
This should fix PR8749

llvm-svn: 122155

1 files changed, 19 insertions, 6 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCFrameInfo.cpp b/llvm/lib/Target/PowerPC/PPCFrameInfo.cpp
index 817b8f166a0..918fb07f57b 100644
--- a/llvm/lib/Target/PowerPC/PPCFrameInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCFrameInfo.cpp
@@ -227,6 +227,17 @@ void PPCFrameInfo::determineFrameLayout(MachineFunction &MF) const {
 // pointer register.
 bool PPCFrameInfo::hasFP(const MachineFunction &MF) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
+  // FIXME: This is pretty much broken by design: hasFP() might be called really
+  // early, before the stack layout was calculated and thus hasFP() might return
+  // true or false here depending on the time of call.
+  return (MFI->getStackSize()) && needsFP(MF);
+}
+
+// needsFP - Return true if the specified function should have a dedicated frame
+// pointer register.  This is true if the function has variable sized allocas or
+// if frame pointer elimination is disabled.
+bool PPCFrameInfo::needsFP(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
 
   // Naked functions have no stack frame pushed, so we don't have a frame
   // pointer.
@@ -267,6 +278,8 @@ void PPCFrameInfo::emitPrologue(MachineFunction &MF) const {
   MBBI = MBB.begin();
 
   // Work out frame sizes.
+  // FIXME: determineFrameLayout() may change the frame size. This should be
+  // moved upper, to some hook.
   determineFrameLayout(MF);
   unsigned FrameSize = MFI->getStackSize();
 
@@ -280,7 +293,7 @@ void PPCFrameInfo::emitPrologue(MachineFunction &MF) const {
   PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
   bool MustSaveLR = FI->mustSaveLR();
   // Do we have a frame pointer for this function?
-  bool HasFP = hasFP(MF) && FrameSize;
+  bool HasFP = hasFP(MF);
 
   int LROffset = PPCFrameInfo::getReturnSaveOffset(isPPC64, isDarwinABI);
 
@@ -516,7 +529,7 @@ void PPCFrameInfo::emitEpilogue(MachineFunction &MF,
   PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
   bool MustSaveLR = FI->mustSaveLR();
   // Do we have a frame pointer for this function?
-  bool HasFP = hasFP(MF) && FrameSize;
+  bool HasFP = hasFP(MF);
 
   int LROffset = PPCFrameInfo::getReturnSaveOffset(isPPC64, isDarwinABI);
 
@@ -735,7 +748,7 @@ PPCFrameInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
   MachineFrameInfo *MFI = MF.getFrameInfo();
 
   // If the frame pointer save index hasn't been defined yet.
-  if (!FPSI && hasFP(MF)) {
+  if (!FPSI && needsFP(MF)) {
     // Find out what the fix offset of the frame pointer save area.
     int FPOffset = getFramePointerSaveOffset(isPPC64, isDarwinABI);
     // Allocate the frame index for frame pointer save area.
@@ -758,7 +771,7 @@ PPCFrameInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
   //        r0 for now.
 
   if (RegInfo->requiresRegisterScavenging(MF)) // FIXME (64-bit): Enable.
-    if (hasFP(MF) || spillsCR(MF)) {
+    if (needsFP(MF) || spillsCR(MF)) {
       const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
       const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
       const TargetRegisterClass *RC = isPPC64 ? G8RC : GPRC;
@@ -779,7 +792,7 @@ void PPCFrameInfo::processFunctionBeforeFrameFinalized(MachineFunction &MF)
   const std::vector<CalleeSavedInfo> &CSI = FFI->getCalleeSavedInfo();
 
   // Early exit if no callee saved registers are modified!
-  if (CSI.empty() && !hasFP(MF)) {
+  if (CSI.empty() && !needsFP(MF)) {
     return;
   }
 
@@ -869,7 +882,7 @@ void PPCFrameInfo::processFunctionBeforeFrameFinalized(MachineFunction &MF)
 
   // Check whether the frame pointer register is allocated. If so, make sure it
   // is spilled to the correct offset.
-  if (hasFP(MF)) {
+  if (needsFP(MF)) {
     HasGPSaveArea = true;
 
     int FI = PFI->getFramePointerSaveIndex();