DWARF requires frame moves be specified at specific times. If you have a

prologue like this:

__Z3fooi:
Leh_func_begin1:
LBB1_0: ## entry
        pushl   %ebp
Llabel1:
        movl    %esp, %ebp
Llabel2:
        pushl   %esi
Llabel3:
        subl    $20, %esp
        call    "L1$pb"
"L1$pb":
        popl    %esi

The "pushl %ebp" needs a table entry specifying the offset. The "movl %esp,
%ebp" makes %ebp the new stack frame register, so that needs to be specified in
DWARF. And "pushl %esi" saves the callee-saved %esi register, which also needs
to be specified in DWARF.

Before, all of this logic was in one method. This didn't work too well, because
as you can see there are multiple FDE line entries that need to be created.

This fix creates the "MachineMove" objects directly when they're needed; instead
of waiting until the end, and losing information.

llvm-svn: 74952

llvm/lib/Target/X86/X86RegisterInfo.cpp

@@ -644,15 +644,16 @@ static int mergeSPUpdates(MachineBasicBlock &MBB,
   return Offset;
 }
 
-void X86RegisterInfo::emitFrameMoves(MachineFunction &MF,
+void X86RegisterInfo::emitCalleeSavedFrameMoves(MachineFunction &MF,
-                                     unsigned FrameLabelId,
+                                                unsigned LabelId) const {
-                                     unsigned ReadyLabelId) const {
   MachineFrameInfo *MFI = MF.getFrameInfo();
   MachineModuleInfo *MMI = MFI->getMachineModuleInfo();
-  if (!MMI)
+  if (!MMI) return;
-    return;
+
+  // Add callee saved registers to move list.
+  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
+  if (CSI.empty()) return;
 
-  uint64_t StackSize = MFI->getStackSize();
   std::vector<MachineMove> &Moves = MMI->getFrameMoves();
   const TargetData *TD = MF.getTarget().getTargetData();
 
@@ -662,62 +663,30 @@ void X86RegisterInfo::emitFrameMoves(MachineFunction &MF,
      TargetFrameInfo::StackGrowsUp ?
      TD->getPointerSize() : -TD->getPointerSize());
 
-  MachineLocation FPDst(hasFP(MF) ? FramePtr : StackPtr);
-  MachineLocation FPSrc(MachineLocation::VirtualFP);
-  Moves.push_back(MachineMove(ReadyLabelId, FPDst, FPSrc));
-
-  if (StackSize) {
-    // Show update of SP.
-    if (hasFP(MF)) {
-      // Adjust SP
-      MachineLocation SPDst(MachineLocation::VirtualFP);
-      MachineLocation SPSrc(MachineLocation::VirtualFP, 2*stackGrowth);
-      Moves.push_back(MachineMove(FrameLabelId, SPDst, SPSrc));
-    } else {
-      MachineLocation SPDst(MachineLocation::VirtualFP);
-      MachineLocation SPSrc(MachineLocation::VirtualFP,
-                            -StackSize+stackGrowth);
-      Moves.push_back(MachineMove(FrameLabelId, SPDst, SPSrc));
-    }
-  } else {
-    // FIXME: Verify & implement for FP
-    MachineLocation SPDst(StackPtr);
-    MachineLocation SPSrc(StackPtr, stackGrowth);
-    Moves.push_back(MachineMove(FrameLabelId, SPDst, SPSrc));
-  }
-
-  // Add callee saved registers to move list.
-  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
-
   // FIXME: This is dirty hack. The code itself is pretty mess right now.
   // It should be rewritten from scratch and generalized sometimes.
 
   // Determine maximum offset (minumum due to stack growth)
   int64_t MaxOffset = 0;
-  for (unsigned I = 0, E = CSI.size(); I!=E; ++I)
+  for (std::vector<CalleeSavedInfo>::const_iterator
+         I = CSI.begin(), E = CSI.end(); I != E; ++I)
     MaxOffset = std::min(MaxOffset,
-                         MFI->getObjectOffset(CSI[I].getFrameIdx()));
+                         MFI->getObjectOffset(I->getFrameIdx()));
 
-  // Calculate offsets
+  // Calculate offsets.
   int64_t saveAreaOffset = (hasFP(MF) ? 3 : 2) * stackGrowth;
-  for (unsigned I = 0, E = CSI.size(); I!=E; ++I) {
+  for (std::vector<CalleeSavedInfo>::const_iterator
-    int64_t Offset = MFI->getObjectOffset(CSI[I].getFrameIdx());
+         I = CSI.begin(), E = CSI.end(); I != E; ++I) {
-    unsigned Reg = CSI[I].getReg();
+    int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
-    Offset = (MaxOffset-Offset+saveAreaOffset);
+    unsigned Reg = I->getReg();
+    Offset = MaxOffset - Offset + saveAreaOffset;
+
     MachineLocation CSDst(MachineLocation::VirtualFP, Offset);
     MachineLocation CSSrc(Reg);
-    Moves.push_back(MachineMove(FrameLabelId, CSDst, CSSrc));
+    Moves.push_back(MachineMove(LabelId, CSDst, CSSrc));
-  }
-
-  if (hasFP(MF)) {
-    // Save FP
-    MachineLocation FPDst(MachineLocation::VirtualFP, 2*stackGrowth);
-    MachineLocation FPSrc(FramePtr);
-    Moves.push_back(MachineMove(ReadyLabelId, FPDst, FPSrc));
   }
 }
 
-
 void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
   MachineFrameInfo *MFI = MF.getFrameInfo();
@@ -729,11 +698,9 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
   bool needsFrameMoves = (MMI && MMI->hasDebugInfo()) ||
                           !Fn->doesNotThrow() ||
                           UnwindTablesMandatory;
+  bool HasFP = hasFP(MF);
   DebugLoc DL;
 
-  // Prepare for frame info.
-  unsigned FrameLabelId = 0;
-
   // Get the number of bytes to allocate from the FrameInfo.
   uint64_t StackSize = MFI->getStackSize();
 
@@ -757,7 +724,7 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
       !MFI->hasCalls() &&                          // No calls.
       !Subtarget->isTargetWin64()) {               // Win64 has no Red Zone
     uint64_t MinSize = X86FI->getCalleeSavedFrameSize();
-    if (hasFP(MF)) MinSize += SlotSize;
+    if (HasFP) MinSize += SlotSize;
     StackSize = std::max(MinSize,
                          StackSize > 128 ? StackSize - 128 : 0);
     MFI->setStackSize(StackSize);
@@ -774,8 +741,16 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
     MI->getOperand(3).setIsDead();
   }
 
+  //  uint64_t StackSize = MFI->getStackSize();
+  std::vector<MachineMove> &Moves = MMI->getFrameMoves();
+  const TargetData *TD = MF.getTarget().getTargetData();
+  int stackGrowth =
+    (MF.getTarget().getFrameInfo()->getStackGrowthDirection() ==
+     TargetFrameInfo::StackGrowsUp ?
+     TD->getPointerSize() : -TD->getPointerSize());
+
   uint64_t NumBytes = 0;
-  if (hasFP(MF)) {
+  if (HasFP) {
     // Calculate required stack adjustment
     uint64_t FrameSize = StackSize - SlotSize;
     if (needsStackRealignment(MF))
@@ -783,19 +758,38 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
 
     NumBytes = FrameSize - X86FI->getCalleeSavedFrameSize();
 
-    // Get the offset of the stack slot for the EBP register... which is
+    // Get the offset of the stack slot for the EBP register, which is
     // guaranteed to be the last slot by processFunctionBeforeFrameFinalized.
     // Update the frame offset adjustment.
     MFI->setOffsetAdjustment(-NumBytes);
 
-    // Save EBP into the appropriate stack slot...
+    // Save EBP/RBP into the appropriate stack slot...
     BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::PUSH64r : X86::PUSH32r))
       .addReg(FramePtr, RegState::Kill);
 
     if (needsFrameMoves) {
       // Mark effective beginning of when frame pointer becomes valid.
-      FrameLabelId = MMI->NextLabelID();
+      unsigned FrameLabelId = MMI->NextLabelID();
       BuildMI(MBB, MBBI, DL, TII.get(X86::DBG_LABEL)).addImm(FrameLabelId);
+
+      // Define the current CFA rule to use the provided offset.
+      if (StackSize) {
+        MachineLocation SPDst(MachineLocation::VirtualFP);
+        MachineLocation SPSrc(MachineLocation::VirtualFP,
+                              HasFP ? 2 * stackGrowth : 
+                                      -StackSize + stackGrowth);
+        Moves.push_back(MachineMove(FrameLabelId, SPDst, SPSrc));
+      } else {
+        // FIXME: Verify & implement for FP
+        MachineLocation SPDst(StackPtr);
+        MachineLocation SPSrc(StackPtr, stackGrowth);
+        Moves.push_back(MachineMove(FrameLabelId, SPDst, SPSrc));
+      }
+
+      // Change the rule for the FramePtr to be an "offset" rule.
+      MachineLocation FPDst(MachineLocation::VirtualFP, 2 * stackGrowth);
+      MachineLocation FPSrc(FramePtr);
+      Moves.push_back(MachineMove(FrameLabelId, FPDst, FPSrc));
     }
 
     // Update EBP with the new base value...
@@ -803,6 +797,16 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
             TII.get(Is64Bit ? X86::MOV64rr : X86::MOV32rr), FramePtr)
         .addReg(StackPtr);
 
+    if (needsFrameMoves) {
+      unsigned FrameLabelId = MMI->NextLabelID();
+      BuildMI(MBB, MBBI, DL, TII.get(X86::DBG_LABEL)).addImm(FrameLabelId);
+
+      // Define the current CFA to use the EBP/RBP register.
+      MachineLocation FPDst(FramePtr);
+      MachineLocation FPSrc(MachineLocation::VirtualFP);
+      Moves.push_back(MachineMove(FrameLabelId, FPDst, FPSrc));
+    }
+
     // Mark the FramePtr as live-in in every block except the entry.
     for (MachineFunction::iterator I = next(MF.begin()), E = MF.end();
          I != E; ++I)
@@ -822,10 +826,22 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
   }
 
   // Skip the callee-saved push instructions.
+  bool RegsSaved = false;
   while (MBBI != MBB.end() &&
          (MBBI->getOpcode() == X86::PUSH32r ||
-          MBBI->getOpcode() == X86::PUSH64r))
+          MBBI->getOpcode() == X86::PUSH64r)) {
+    RegsSaved = true;
     ++MBBI;
+  }
+
+  if (RegsSaved && needsFrameMoves) {
+    // Mark end of callee-saved push instructions.
+    unsigned LabelId = MMI->NextLabelID();
+    BuildMI(MBB, MBBI, DL, TII.get(X86::DBG_LABEL)).addImm(LabelId);
+
+    // Emit DWARF info specifying the offsets of the callee-saved registers.
+    emitCalleeSavedFrameMoves(MF, LabelId);
+  }
 
   if (MBBI != MBB.end())
     DL = MBBI->getDebugLoc();
@@ -882,14 +898,6 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
     if (NumBytes)
       emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, TII);
   }
-
-  if (needsFrameMoves) {
-    unsigned ReadyLabelId = 0;
-    // Mark effective beginning of when frame pointer is ready.
-    ReadyLabelId = MMI->NextLabelID();
-    BuildMI(MBB, MBBI, DL, TII.get(X86::DBG_LABEL)).addImm(ReadyLabelId);
-    emitFrameMoves(MF, FrameLabelId, ReadyLabelId);
-  }
 }
 
 void X86RegisterInfo::emitEpilogue(MachineFunction &MF,

llvm/lib/Target/X86/X86RegisterInfo.h

@@ -136,12 +136,10 @@ public:
   void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                             RegScavenger *RS = NULL) const;
 
+  void emitCalleeSavedFrameMoves(MachineFunction &MF, unsigned LabelId) const;
   void emitPrologue(MachineFunction &MF) const;
   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const;
 
-  void emitFrameMoves(MachineFunction &MF,
-                      unsigned FrameLabelId, unsigned ReadyLabelId) const;
-
   // Debug information queries.
   unsigned getRARegister() const;
   unsigned getFrameRegister(MachineFunction &MF) const;