Teach MachineFrameInfo to track maximum alignment while stack objects are being

created. This ensures it's updated at all time. It means targets which perform
dynamic stack alignment would know whether it is required and whether frame
pointer register cannot be made available register allocation.
This is a fix for rdar://7625239. Sorry, I can't create a reasonably sized test
case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96069 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/MachineFrameInfo.h b/include/llvm/CodeGen/MachineFrameInfo.h
index 968e4eae3a695494ec11d1e04161339323aa9223..043e97f9a7cd3123f55424a4dac70cf9eaa21c2c 100644 (file)
--- a/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/include/llvm/CodeGen/MachineFrameInfo.h
@@ -276,6 +276,7 @@ public:
     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
            "Invalid Object Idx!");
     Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
+    MaxAlignment = std::max(MaxAlignment, Align);
   }
 
   /// getObjectOffset - Return the assigned stack offset of the specified object
@@ -328,19 +329,6 @@ public:
   ///
   void setMaxAlignment(unsigned Align) { MaxAlignment = Align; }
 
-  /// calculateMaxStackAlignment() - If there is a local object which requires
-  /// greater alignment than the current max alignment, adjust accordingly.
-  void calculateMaxStackAlignment() {
-    for (int i = getObjectIndexBegin(),
-         e = getObjectIndexEnd(); i != e; ++i) {
-      if (isDeadObjectIndex(i))
-        continue;
-
-      unsigned Align = getObjectAlignment(i);
-      MaxAlignment = std::max(MaxAlignment, Align);
-    }
-  }
-
   /// hasCalls - Return true if the current function has no function calls.
   /// This is only valid during or after prolog/epilog code emission.
   ///
@@ -402,6 +390,7 @@ public:
     Objects.push_back(StackObject(Size, Alignment, 0, false, isSS));
     int Index = (int)Objects.size()-NumFixedObjects-1;
     assert(Index >= 0 && "Bad frame index!");
+    MaxAlignment = std::max(MaxAlignment, Alignment);
     return Index;
   }
 
@@ -412,6 +401,7 @@ public:
   int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
     CreateStackObject(Size, Alignment, true);
     int Index = (int)Objects.size()-NumFixedObjects-1;
+    MaxAlignment = std::max(MaxAlignment, Alignment);
     return Index;
   }
 

diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index 036f59a2a5812fc1a1e72b0fec2e09c4d944d02c..040259e15c529e73c4775e5416f5d50e47931732 100644 (file)
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/lib/CodeGen/PrologEpilogInserter.cpp
@@ -476,8 +476,6 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
   // Loop over all of the stack objects, assigning sequential addresses...
   MachineFrameInfo *FFI = Fn.getFrameInfo();
 
-  unsigned MaxAlign = 1;
-
   // Start at the beginning of the local area.
   // The Offset is the distance from the stack top in the direction
   // of stack growth -- so it's always nonnegative.
@@ -517,9 +515,6 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
       Offset += FFI->getObjectSize(i);
 
       unsigned Align = FFI->getObjectAlignment(i);
-      // If the alignment of this object is greater than that of the stack,
-      // then increase the stack alignment to match.
-      MaxAlign = std::max(MaxAlign, Align);
       // Adjust to alignment boundary
       Offset = (Offset+Align-1)/Align*Align;
 
@@ -529,9 +524,6 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
     int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
     for (int i = MaxCSFI; i >= MinCSFI ; --i) {
       unsigned Align = FFI->getObjectAlignment(i);
-      // If the alignment of this object is greater than that of the stack,
-      // then increase the stack alignment to match.
-      MaxAlign = std::max(MaxAlign, Align);
       // Adjust to alignment boundary
       Offset = (Offset+Align-1)/Align*Align;
 
@@ -540,6 +532,8 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
     }
   }
 
+  unsigned MaxAlign = FFI->getMaxAlignment();
+
   // Make sure the special register scavenging spill slot is closest to the
   // frame pointer if a frame pointer is required.
   const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
@@ -605,11 +599,6 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
 
   // Update frame info to pretend that this is part of the stack...
   FFI->setStackSize(Offset - LocalAreaOffset);
-
-  // Remember the required stack alignment in case targets need it to perform
-  // dynamic stack alignment.
-  if (MaxAlign > FFI->getMaxAlignment())
-    FFI->setMaxAlignment(MaxAlign);
 }
 
 

diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index cb0bd1dbd240750ce11fa30e66743793f8187efa..91e3550d077caa8e1cc1784f4d1a84a87e7ea0c6 100644 (file)
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -583,14 +583,6 @@ ARMBaseRegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
   SmallVector<unsigned, 4> UnspilledCS2GPRs;
   ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
 
-
-  // Calculate and set max stack object alignment early, so we can decide
-  // whether we will need stack realignment (and thus FP).
-  if (RealignStack) {
-    MachineFrameInfo *MFI = MF.getFrameInfo();
-    MFI->calculateMaxStackAlignment();
-  }
-
   // Spill R4 if Thumb2 function requires stack realignment - it will be used as
   // scratch register.
   // FIXME: It will be better just to find spare register here.

diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 081c6d9061f0df28de943d4b6d4062412d689286..85242368c3cf9f8df14088f1e1206f6e2adf10ad 100644 (file)
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -485,7 +485,7 @@ X86RegisterInfo::getFrameIndexOffset(const MachineFunction &MF, int FI) const {
       Offset += SlotSize;
     } else {
       unsigned Align = MFI->getObjectAlignment(FI);
-      assert( (-(Offset + StackSize)) % Align == 0);
+      assert((-(Offset + StackSize)) % Align == 0);
       Align = 0;
       return Offset + StackSize;
     }
@@ -627,10 +627,6 @@ X86RegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                                       RegScavenger *RS) const {
   MachineFrameInfo *MFI = MF.getFrameInfo();
 
-  // Calculate and set max stack object alignment early, so we can decide
-  // whether we will need stack realignment (and thus FP).
-  MFI->calculateMaxStackAlignment();
-
   X86MachineFunctionInfo *X86FI = MF.getInfo<X86MachineFunctionInfo>();
   int32_t TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();