Recommit r74952 with a bug fix:

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.

There is some ugliness where we generate code like this:

LBB22_0:	## entry
	pushl	%ebp
Llabel280:
	movl	%esp, %ebp
Llabel281:
Llabel284:
	pushl	%ebp  <----------
	pushl	%ebx
	pushl	%edi
	pushl	%esi
Llabel282:
	subl	$328, %esp

Notice the extra "pushl %ebp". If we generate a "machine move" instruction in
the FDE for that pushl, the linker may get very confused about what value %ebp
should have when exitting the function. I.e., it'll give it the value %esp
instead of the %ebp value from the first "pushl". Not to mention that, in this
case, %ebp isn't modified in the function (that's a separate bug). I put a small
hack in to get it to work. It might be the only solution, but should be
revisited once the above case is fixed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75047 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index a2f319f9a7ab769ec11d9347722dd8d00fc5120f..5b43d21d8e1a3258d00d9a288452bf1dda3a1357 100644 (file)
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -644,17 +644,20 @@ static int mergeSPUpdates(MachineBasicBlock &MBB,
   return Offset;
 }
 
-void X86RegisterInfo::emitFrameMoves(MachineFunction &MF,
-                                     unsigned FrameLabelId,
-                                     unsigned ReadyLabelId) const {
+void X86RegisterInfo::emitCalleeSavedFrameMoves(MachineFunction &MF,
+                                                unsigned LabelId,
+                                                unsigned FramePtr) const {
   MachineFrameInfo *MFI = MF.getFrameInfo();
   MachineModuleInfo *MMI = MFI->getMachineModuleInfo();
-  if (!MMI)
-    return;
+  if (!MMI) 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();
+  bool HasFP = hasFP(MF);
 
   // Calculate amount of bytes used for return address storing
   int stackGrowth =
@@ -662,62 +665,53 @@ 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()));
-
-  // Calculate offsets
-  int64_t saveAreaOffset = (hasFP(MF) ? 3 : 2)*stackGrowth;
-  for (unsigned I = 0, E = CSI.size(); I!=E; ++I) {
-    int64_t Offset = MFI->getObjectOffset(CSI[I].getFrameIdx());
-    unsigned Reg = CSI[I].getReg();
-    Offset = (MaxOffset-Offset+saveAreaOffset);
+                         MFI->getObjectOffset(I->getFrameIdx()));
+
+  // Calculate offsets.
+  int64_t saveAreaOffset = (HasFP ? 3 : 2) * stackGrowth;
+  for (std::vector<CalleeSavedInfo>::const_iterator
+         I = CSI.begin(), E = CSI.end(); I != E; ++I) {
+    int64_t Offset = MFI->getObjectOffset(I->getFrameIdx());
+    unsigned Reg = I->getReg();
+    Offset = MaxOffset - Offset + saveAreaOffset;
+
+    // Don't output a new machine move if we're re-saving the frame
+    // pointer. This happens when the PrologEpilogInserter has inserted an extra
+    // "PUSH" of the frame pointer -- the "emitPrologue" method automatically
+    // generates one when frame pointers are used. If we generate a "machine
+    // move" for this extra "PUSH", the linker will lose track of the fact that
+    // the frame pointer should have the value of the first "PUSH" when it's
+    // trying to unwind.
+    // 
+    // FIXME: This looks inelegant. It's possibly correct, but it's covering up
+    //        another bug. I.e., one where we generate a prolog like this:
+    //
+    //          pushl  %ebp
+    //          movl   %esp, %ebp
+    //          pushl  %ebp
+    //          pushl  %esi
+    //           ...
+    //
+    //        The immediate re-push of EBP is unnecessary. At the least, it's an
+    //        optimization bug. EBP can be used as a scratch register in certain
+    //        cases, but probably not when we have a frame pointer.
+    if (HasFP && FramePtr == Reg)
+      continue;
+
     MachineLocation CSDst(MachineLocation::VirtualFP, Offset);
     MachineLocation CSSrc(Reg);
-    Moves.push_back(MachineMove(FrameLabelId, CSDst, CSSrc));
-  }
-
-  if (hasFP(MF)) {
-    // Save FP
-    MachineLocation FPDst(MachineLocation::VirtualFP, 2*stackGrowth);
-    MachineLocation FPSrc(FramePtr);
-    Moves.push_back(MachineMove(ReadyLabelId, FPDst, FPSrc));
+    Moves.push_back(MachineMove(LabelId, CSDst, CSSrc));
   }
 }
 
-
 void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
   MachineFrameInfo *MFI = MF.getFrameInfo();
@@ -729,11 +723,9 @@ 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 +749,7 @@ 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 +766,16 @@ 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 +783,38 @@ 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 +822,16 @@ 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)
@@ -814,6 +843,7 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
         BuildMI(MBB, MBBI, DL,
                 TII.get(Is64Bit ? X86::AND64ri32 : X86::AND32ri),
                 StackPtr).addReg(StackPtr).addImm(-MaxAlign);
+
       // The EFLAGS implicit def is dead.
       MI->getOperand(3).setIsDead();
     }
@@ -822,10 +852,22 @@ 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, FramePtr);
+  }
 
   if (MBBI != MBB.end())
     DL = MBBI->getDebugLoc();
@@ -882,14 +924,6 @@ 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,

diff --git a/lib/Target/X86/X86RegisterInfo.h b/lib/Target/X86/X86RegisterInfo.h
index 33b9f5edc73a6ed1daa179836bc41635d87c40ac..e1a23cb4edbfc2cce6b2fe75cf1535a2b292e59b 100644 (file)
--- a/lib/Target/X86/X86RegisterInfo.h
+++ b/lib/Target/X86/X86RegisterInfo.h
@@ -136,12 +136,11 @@ public:
   void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                             RegScavenger *RS = NULL) const;
 
+  void emitCalleeSavedFrameMoves(MachineFunction &MF, unsigned LabelId,
+                                 unsigned FramePtr) 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;