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


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122155 91177308-0d34-0410-b5e6-96231b3b80d8

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();

lib/Target/PowerPC/PPCFrameInfo.h

@@ -38,6 +38,7 @@ public:
   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const;
 
   bool hasFP(const MachineFunction &MF) const;
+  bool needsFP(const MachineFunction &MF) const;
   void getInitialFrameState(std::vector<MachineMove> &Moves) const;
 
   void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,

lib/Target/PowerPC/PPCRegisterInfo.cpp

@@ -258,7 +258,8 @@ PPCRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
 
 BitVector PPCRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
   BitVector Reserved(getNumRegs());
-  const TargetFrameInfo *TFI = MF.getTarget().getFrameInfo();
+  const PPCFrameInfo *PPCFI =
+    static_cast<const PPCFrameInfo*>(MF.getTarget().getFrameInfo());
 
   Reserved.set(PPC::R0);
   Reserved.set(PPC::R1);
@@ -305,7 +306,7 @@ BitVector PPCRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
     }
   }
 
-  if (TFI->hasFP(MF))
+  if (PPCFI->needsFP(MF))
     Reserved.set(PPC::R31);
 
   return Reserved;

lib/Target/PowerPC/PPCRegisterInfo.td

@@ -301,12 +301,13 @@ def GPRC : RegisterClass<"PPC", [i32], 32,
       // When using the 32-bit SVR4 ABI, r13 is reserved for the Small Data Area
       // pointer.
       const PPCSubtarget &Subtarget = MF.getTarget().getSubtarget<PPCSubtarget>();
-      const TargetFrameInfo *TFI = MF.getTarget().getFrameInfo();
+      const PPCFrameInfo *PPCFI =
+        static_cast<const PPCFrameInfo*>(MF.getTarget().getFrameInfo());
    
       if (Subtarget.isPPC64() || Subtarget.isSVR4ABI())
         return end()-5;  // don't allocate R13, R31, R0, R1, LR
         
-      if (TFI->hasFP(MF))
+      if (PPCFI->needsFP(MF))
         return end()-4;  // don't allocate R31, R0, R1, LR
       else
         return end()-3;  // don't allocate R0, R1, LR
@@ -331,8 +332,9 @@ def G8RC : RegisterClass<"PPC", [i64], 64,
     }
     G8RCClass::iterator
     G8RCClass::allocation_order_end(const MachineFunction &MF) const {
-      const TargetFrameInfo *TFI = MF.getTarget().getFrameInfo();
-      if (TFI->hasFP(MF))
+      const PPCFrameInfo *PPCFI =
+        static_cast<const PPCFrameInfo*>(MF.getTarget().getFrameInfo());
+      if (PPCFI->needsFP(MF))
         return end()-5;
       else
         return end()-4;

test/CodeGen/PowerPC/2010-12-18-PPCStackRefs.ll

@@ -0,0 +1,22 @@
+; RUN: llc -disable-fp-elim < %s | FileCheck %s
+; PR8749
+target datalayout = "E-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f128:64:128-n32"
+target triple = "powerpc-apple-darwin9.8"
+
+define i32 @main() nounwind {
+entry:
+; Make sure we're generating references using the red zone
+; CHECK: main:
+; CHECK: stw r3, -12(r1)
+  %retval = alloca i32
+  %0 = alloca i32
+  %"alloca point" = bitcast i32 0 to i32
+  store i32 0, i32* %0, align 4
+  %1 = load i32* %0, align 4
+  store i32 %1, i32* %retval, align 4
+  br label %return
+
+return:                                           ; preds = %entry
+  %retval1 = load i32* %retval
+  ret i32 %retval1
+}