[LLVM][Alignment] Introduce Alignment In MachineFrameInfo

[gchatelet]

Summary

This is patch is part of a serie to introduce an Alignment type.
See this thread for context: http://lists.llvm.org/pipermail/llvm-dev/2019-July/133851.html
See this patch for the introduction of the type: https://reviews.llvm.org/D64790

[gchatelet]

Converting all alignements in MachineFrameInfo.

[gchatelet]

All the tests are passing but I'm not entirely sure of the validity of this patch.
Alignment, StackAlignment seems to be always defined alignment (aka. Align) but I'm not so sure of MaxAlignment and LocalFrameMaxAlign.
Hexagon/HexagonFrameLowering.cpp seem to rely on the fact that LocalFrameMaxAlign is undefined.
I'm not sure about MaxAlignment.

[gchatelet]

• Using Align for LocalFrameMaxAlign instead of MaybeAlign

[kparzysz]

The Hexagon part looks ok.

[gchatelet]

In D65800#1621111, @kparzysz wrote:

The Hexagon part looks ok.

Thx!

[gchatelet]

rebasing

[hfinkel]

LGTM

[gchatelet]

Thx @hfinkel

llvm/include/llvm/CodeGen/MachineFrameInfo.h

 //===-- CodeGen/MachineFrameInfo.h - Abstract Stack Frame Rep. --*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // The file defines the MachineFrameInfo class.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CODEGEN_MACHINEFRAMEINFO_H
 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
 
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Alignment.h"
 #include "llvm/Support/DataTypes.h"
 #include <cassert>
 #include <vector>
 
 namespace llvm {
 class raw_ostream;
 class MachineFunction;
 class MachineBasicBlock;
struct StackObject {
     // the function.  This field has no meaning for a variable sized element.
     int64_t SPOffset;
 
     // The size of this object on the stack. 0 means a variable sized object,
     // ~0ULL means a dead object.
     uint64_t Size;
 
     // The required alignment of this stack slot.
-    unsigned Alignment;
+    Align Alignment;
 
     // If true, the value of the stack object is set before
     // entering the function and is not modified inside the function. By
     // default, fixed objects are immutable unless marked otherwise.
     bool isImmutable;
 
     // If true the stack object is used as spill slot. It
     // cannot alias any other memory objects.
struct StackObject {
     /// If true, the object has been zero-extended.
     bool isZExt = false;
 
     /// If true, the object has been zero-extended.
     bool isSExt = false;
 
     uint8_t SSPLayout;
 
-    StackObject(uint64_t Size, unsigned Alignment, int64_t SPOffset,
+    StackObject(uint64_t Size, llvm::Align Alignment, int64_t SPOffset,
                 bool IsImmutable, bool IsSpillSlot, const AllocaInst *Alloca,
                 bool IsAliased, uint8_t StackID = 0)
         : SPOffset(SPOffset), Size(Size), Alignment(Alignment),
-        isImmutable(IsImmutable), isSpillSlot(IsSpillSlot),
-        StackID(StackID), Alloca(Alloca), isAliased(IsAliased),
-        SSPLayout(SSPLK_None) {}
+          isImmutable(IsImmutable), isSpillSlot(IsSpillSlot), StackID(StackID),
+          Alloca(Alloca), isAliased(IsAliased), SSPLayout(SSPLK_None) {}
   };
 
   /// The alignment of the stack.
-  unsigned StackAlignment;
+  Align StackAlignment;
 
   /// Can the stack be realigned. This can be false if the target does not
   /// support stack realignment, or if the user asks us not to realign the
   /// stack. In this situation, overaligned allocas are all treated as dynamic
   /// allocations and the target must handle them as part of DYNAMIC_STACKALLOC
   /// lowering. All non-alloca stack objects have their alignment clamped to the
   /// base ABI stack alignment.
   /// FIXME: There is room for improvement in this case, in terms of
private:
 
   /// The prolog/epilog code inserter may process objects that require greater
   /// alignment than the default alignment the target provides.
   /// To handle this, MaxAlignment is set to the maximum alignment
   /// needed by the objects on the current frame.  If this is greater than the
   /// native alignment maintained by the compiler, dynamic alignment code will
   /// be needed.
   ///
-  unsigned MaxAlignment = 0;
+  Align MaxAlignment;
 
   /// Set to true if this function adjusts the stack -- e.g.,
   /// when calling another function. This is only valid during and after
   /// prolog/epilog code insertion.
   bool AdjustsStack = false;
 
   /// Set to true if this function has any function calls.
   bool HasCalls = false;
private:
   /// into the local frame allocation block. <FrameIdx, LocalOffset>
   SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
 
   /// Size of the pre-allocated local frame block.
   int64_t LocalFrameSize = 0;
 
   /// Required alignment of the local object blob, which is the strictest
   /// alignment of any object in it.
-  unsigned LocalFrameMaxAlign = 0;
+  Align LocalFrameMaxAlign;
 
   /// Whether the local object blob needs to be allocated together. If not,
   /// PEI should ignore the isPreAllocated flags on the stack objects and
   /// just allocate them normally.
   bool UseLocalStackAllocationBlock = false;
 
   /// True if the function dynamically adjusts the stack pointer through some
   /// opaque mechanism like inline assembly or Win32 EH.
private:
   /// Not null, if shrink-wrapping found a better place for the prologue.
   MachineBasicBlock *Save = nullptr;
   /// Not null, if shrink-wrapping found a better place for the epilogue.
   MachineBasicBlock *Restore = nullptr;
 
 public:
   explicit MachineFrameInfo(unsigned StackAlignment, bool StackRealignable,
                             bool ForcedRealign)
-      : StackAlignment(StackAlignment), StackRealignable(StackRealignable),
-        ForcedRealign(ForcedRealign) {}
+      : StackAlignment(assumeAligned(StackAlignment)),
+        StackRealignable(StackRealignable), ForcedRealign(ForcedRealign) {}
 
   /// Return true if there are any stack objects in this function.
   bool hasStackObjects() const { return !Objects.empty(); }
 
   /// This method may be called any time after instruction
   /// selection is complete to determine if the stack frame for this function
   /// contains any variable sized objects.
   bool hasVarSizedObjects() const { return HasVarSizedObjects; }
public:
   /// Set the size of the local object blob.
   void setLocalFrameSize(int64_t sz) { LocalFrameSize = sz; }
 
   /// Get the size of the local object blob.
   int64_t getLocalFrameSize() const { return LocalFrameSize; }
 
   /// Required alignment of the local object blob,
   /// which is the strictest alignment of any object in it.
-  void setLocalFrameMaxAlign(unsigned Align) { LocalFrameMaxAlign = Align; }
+  void setLocalFrameMaxAlign(Align Align) { LocalFrameMaxAlign = Align; }
 
   /// Return the required alignment of the local object blob.
-  unsigned getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
+  Align getLocalFrameMaxAlign() const { return LocalFrameMaxAlign; }
 
   /// Get whether the local allocation blob should be allocated together or
   /// let PEI allocate the locals in it directly.
   bool getUseLocalStackAllocationBlock() const {
     return UseLocalStackAllocationBlock;
   }
 
   /// setUseLocalStackAllocationBlock - Set whether the local allocation blob
assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
            "Invalid Object Idx!");
     Objects[ObjectIdx+NumFixedObjects].Size = Size;
   }
 
   /// Return the alignment of the specified stack object.
   unsigned getObjectAlignment(int ObjectIdx) const {
     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
            "Invalid Object Idx!");
-    return Objects[ObjectIdx+NumFixedObjects].Alignment;
+    return Objects[ObjectIdx + NumFixedObjects].Alignment.value();
   }
 
   /// setObjectAlignment - Change the alignment of the specified stack object.
   void setObjectAlignment(int ObjectIdx, unsigned Align) {
     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
            "Invalid Object Idx!");
-    Objects[ObjectIdx+NumFixedObjects].Alignment = Align;
+    Objects[ObjectIdx + NumFixedObjects].Alignment = assumeAligned(Align);
 
     // Only ensure max alignment for the default stack.
     if (getStackID(ObjectIdx) == 0)
       ensureMaxAlignment(Align);
   }
 
   /// Return the underlying Alloca of the specified
   /// stack object if it exists. Returns 0 if none exists.
public:
   /// Return the correction for frame offsets.
   int getOffsetAdjustment() const { return OffsetAdjustment; }
 
   /// Set the correction for frame offsets.
   void setOffsetAdjustment(int Adj) { OffsetAdjustment = Adj; }
 
   /// Return the alignment in bytes that this function must be aligned to,
   /// which is greater than the default stack alignment provided by the target.
-  unsigned getMaxAlignment() const { return MaxAlignment; }
+  unsigned getMaxAlignment() const { return MaxAlignment.value(); }
 
   /// Make sure the function is at least Align bytes aligned.
-  void ensureMaxAlignment(unsigned Align);
+  void ensureMaxAlignment(llvm::Align Align);
+  /// FIXME: Remove this once transition to Align is over.
+  inline void ensureMaxAlignment(unsigned Align) {
+    ensureMaxAlignment(assumeAligned(Align));
+  }
 
   /// Return true if this function adjusts the stack -- e.g.,
   /// when calling another function. This is only valid during and after
   /// prolog/epilog code insertion.
   bool adjustsStack() const { return AdjustsStack; }
   void setAdjustsStack(bool V) { AdjustsStack = V; }
 
   /// Return true if the current function has any function calls.
void markAsStatepointSpillSlotObjectIndex(int ObjectIdx) {
     assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
            "Invalid Object Idx!");
     Objects[ObjectIdx+NumFixedObjects].isStatepointSpillSlot = true;
     assert(isStatepointSpillSlotObjectIndex(ObjectIdx) && "inconsistent");
   }
 
   /// Create a new statically sized stack object, returning
   /// a nonnegative identifier to represent it.
-  int CreateStackObject(uint64_t Size, unsigned Alignment, bool isSpillSlot,
+  int CreateStackObject(uint64_t Size, llvm::Align Alignment, bool isSpillSlot,
                         const AllocaInst *Alloca = nullptr, uint8_t ID = 0);
+  /// FIXME: Remove this function when transition to llvm::Align is over.
+  inline int CreateStackObject(uint64_t Size, unsigned Alignment,
+                               bool isSpillSlot,
+                               const AllocaInst *Alloca = nullptr,
+                               uint8_t ID = 0) {
+    return CreateStackObject(Size, assumeAligned(Alignment), isSpillSlot,
+                             Alloca, ID);
+  }
 
   /// Create a new statically sized stack object that represents a spill slot,
   /// returning a nonnegative identifier to represent it.
-  int CreateSpillStackObject(uint64_t Size, unsigned Alignment);
+  int CreateSpillStackObject(uint64_t Size, llvm::Align Alignment);
+  /// FIXME: Remove this function when transition to llvm::Align is over.
+  inline int CreateSpillStackObject(uint64_t Size, unsigned Alignment) {
+    return CreateSpillStackObject(Size, assumeAligned(Alignment));
+  }
 
   /// Remove or mark dead a statically sized stack object.
   void RemoveStackObject(int ObjectIdx) {
     // Mark it dead.
     Objects[ObjectIdx+NumFixedObjects].Size = ~0ULL;
   }
 
   /// Notify the MachineFrameInfo object that a variable sized object has been
   /// created.  This must be created whenever a variable sized object is
   /// created, whether or not the index returned is actually used.
-  int CreateVariableSizedObject(unsigned Alignment, const AllocaInst *Alloca);
+  int CreateVariableSizedObject(llvm::Align Alignment,
+                                const AllocaInst *Alloca);
+  /// FIXME: Remove this function when transition to llvm::Align is over.
+  int CreateVariableSizedObject(unsigned Alignment, const AllocaInst *Alloca) {
+    return CreateVariableSizedObject(assumeAligned(Alignment), Alloca);
+  }
 
   /// Returns a reference to call saved info vector for the current function.
   const std::vector<CalleeSavedInfo> &getCalleeSavedInfo() const {
     return CSInfo;
   }
   /// \copydoc getCalleeSavedInfo()
   std::vector<CalleeSavedInfo> &getCalleeSavedInfo() { return CSInfo; }
 

llvm/lib/Analysis/MemoryBuiltins.cpp

 
 STATISTIC(ObjectVisitorArgument,
           "Number of arguments with unsolved size and offset");
 STATISTIC(ObjectVisitorLoad,
           "Number of load instructions with unsolved size and offset");
 
 APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) {
   if (Options.RoundToAlign && Align)
-    return APInt(IntTyBits, alignTo(Size.getZExtValue(), Align));
+    return APInt(IntTyBits, alignTo(Size.getZExtValue(), llvm::Align(Align)));
   return Size;
 }
 
 ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
                                                  const TargetLibraryInfo *TLI,
                                                  LLVMContext &Context,
                                                  ObjectSizeOpts Options)
     : DL(DL), TLI(TLI), Options(Options) {

llvm/lib/CodeGen/LocalStackSlotAllocation.cpp

for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
     if (ProtectedObjs.count(i))
       continue;
 
     AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
   }
 
   // Remember how big this blob of stack space is
   MFI.setLocalFrameSize(Offset);
-  MFI.setLocalFrameMaxAlign(MaxAlign);
+  MFI.setLocalFrameMaxAlign(assumeAligned(MaxAlign));
 }
 
 static inline bool
 lookupCandidateBaseReg(unsigned BaseReg,
                        int64_t BaseOffset,
                        int64_t FrameSizeAdjust,
                        int64_t LocalFrameOffset,
                        const MachineInstr &MI,

llvm/lib/CodeGen/MachineFrameInfo.cpp

 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include <cassert>
 
 #define DEBUG_TYPE "codegen"
 
 using namespace llvm;
 
-void MachineFrameInfo::ensureMaxAlignment(unsigned Align) {
+void MachineFrameInfo::ensureMaxAlignment(llvm::Align Align) {
   if (!StackRealignable)
     assert(Align <= StackAlignment &&
            "For targets without stack realignment, Align is out of limit!");
   if (MaxAlignment < Align) MaxAlignment = Align;
 }
 
 /// Clamp the alignment if requested and emit a warning.
-static inline unsigned clampStackAlignment(bool ShouldClamp, unsigned Align,
-                                           unsigned StackAlign) {
+static inline llvm::Align clampStackAlignment(bool ShouldClamp,
+                                              llvm::Align Align,
+                                              llvm::Align StackAlign) {
   if (!ShouldClamp || Align <= StackAlign)
     return Align;
-  LLVM_DEBUG(dbgs() << "Warning: requested alignment " << Align
-                    << " exceeds the stack alignment " << StackAlign
+  LLVM_DEBUG(dbgs() << "Warning: requested alignment " << Align.value()
+                    << " exceeds the stack alignment " << StackAlign.value()
                     << " when stack realignment is off" << '\n');
   return StackAlign;
 }
 
-int MachineFrameInfo::CreateStackObject(uint64_t Size, unsigned Alignment,
+int MachineFrameInfo::CreateStackObject(uint64_t Size, llvm::Align Alignment,
                                         bool IsSpillSlot,
                                         const AllocaInst *Alloca,
                                         uint8_t StackID) {
   assert(Size != 0 && "Cannot allocate zero size stack objects!");
   Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
   Objects.push_back(StackObject(Size, Alignment, 0, false, IsSpillSlot, Alloca,
                                 !IsSpillSlot, StackID));
   int Index = (int)Objects.size() - NumFixedObjects - 1;
   assert(Index >= 0 && "Bad frame index!");
   if (StackID == 0)
     ensureMaxAlignment(Alignment);
   return Index;
 }
 
 int MachineFrameInfo::CreateSpillStackObject(uint64_t Size,
-                                             unsigned Alignment) {
+                                             llvm::Align Alignment) {
   Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
   CreateStackObject(Size, Alignment, true);
   int Index = (int)Objects.size() - NumFixedObjects - 1;
   ensureMaxAlignment(Alignment);
   return Index;
 }
 
-int MachineFrameInfo::CreateVariableSizedObject(unsigned Alignment,
+int MachineFrameInfo::CreateVariableSizedObject(llvm::Align Alignment,
                                                 const AllocaInst *Alloca) {
   HasVarSizedObjects = true;
   Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
   Objects.push_back(StackObject(0, Alignment, 0, false, false, Alloca, true));
   ensureMaxAlignment(Alignment);
   return (int)Objects.size()-NumFixedObjects-1;
 }
 
 int MachineFrameInfo::CreateFixedObject(uint64_t Size, int64_t SPOffset,
                                         bool IsImmutable, bool IsAliased) {
   assert(Size != 0 && "Cannot allocate zero size fixed stack objects!");
   // The alignment of the frame index can be determined from its offset from
   // the incoming frame position.  If the frame object is at offset 32 and
   // the stack is guaranteed to be 16-byte aligned, then we know that the
   // object is 16-byte aligned. Note that unlike the non-fixed case, if the
   // stack needs realignment, we can't assume that the stack will in fact be
   // aligned.
-  unsigned Alignment = MinAlign(SPOffset, ForcedRealign ? 1 : StackAlignment);
+  llvm::Align Alignment =
+      commonAlignment(ForcedRealign ? llvm::Align() : StackAlignment, SPOffset);
   Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
   Objects.insert(Objects.begin(),
                  StackObject(Size, Alignment, SPOffset, IsImmutable,
                              /*IsSpillSlot=*/false, /*Alloca=*/nullptr,
                              IsAliased));
   return -++NumFixedObjects;
 }
 
 int MachineFrameInfo::CreateFixedSpillStackObject(uint64_t Size,
                                                   int64_t SPOffset,
                                                   bool IsImmutable) {
-  unsigned Alignment = MinAlign(SPOffset, ForcedRealign ? 1 : StackAlignment);
+  llvm::Align Alignment =
+      commonAlignment(ForcedRealign ? llvm::Align() : StackAlignment, SPOffset);
   Alignment = clampStackAlignment(!StackRealignable, Alignment, StackAlignment);
   Objects.insert(Objects.begin(),
                  StackObject(Size, Alignment, SPOffset, IsImmutable,
                              /*IsSpillSlot=*/true, /*Alloca=*/nullptr,
                              /*IsAliased=*/false));
   return -++NumFixedObjects;
 }
 
for (unsigned i = 0, e = Objects.size(); i != e; ++i) {
     if (SO.Size == ~0ULL) {
       OS << "dead\n";
       continue;
     }
     if (SO.Size == 0)
       OS << "variable sized";
     else
       OS << "size=" << SO.Size;
-    OS << ", align=" << SO.Alignment;
+    OS << ", align=" << SO.Alignment.value();
 
     if (i < NumFixedObjects)
       OS << ", fixed";
     if (i < NumFixedObjects || SO.SPOffset != -1) {
       int64_t Off = SO.SPOffset - ValOffset;
       OS << ", at location [SP";
       if (Off > 0)
         OS << "+" << Off;

llvm/lib/CodeGen/PrologEpilogInserter.cpp

for (SmallVectorImpl<int>::iterator I = SFIs.begin(),
       AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign, Skew);
   }
 
   // FIXME: Once this is working, then enable flag will change to a target
   // check for whether the frame is large enough to want to use virtual
   // frame index registers. Functions which don't want/need this optimization
   // will continue to use the existing code path.
   if (MFI.getUseLocalStackAllocationBlock()) {
-    unsigned Align = MFI.getLocalFrameMaxAlign();
+    unsigned Align = MFI.getLocalFrameMaxAlign().value();
 
     // Adjust to alignment boundary.
     Offset = alignTo(Offset, Align, Skew);
 
     LLVM_DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
 
     // Resolve offsets for objects in the local block.
     for (unsigned i = 0, e = MFI.getLocalFrameObjectCount(); i != e; ++i) {

llvm/lib/Target/Hexagon/HexagonFrameLowering.cpp

for (int i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
     // stores if they happen here.
     unsigned A = std::max(MFI.getObjectAlignment(i), 8U);
     MFI.setObjectAlignment(i, 8);
     LFS = alignTo(LFS+S, A);
     MFI.mapLocalFrameObject(i, -LFS);
   }
 
   MFI.setLocalFrameSize(LFS);
-  unsigned A = MFI.getLocalFrameMaxAlign();
+  Align A = MFI.getLocalFrameMaxAlign();
   assert(A <= 8 && "Unexpected local frame alignment");
-  if (A == 0)
-    MFI.setLocalFrameMaxAlign(8);
+  if (A == 1)
+    MFI.setLocalFrameMaxAlign(llvm::Align(8));
   MFI.setUseLocalStackAllocationBlock(true);
 
   // Set the physical aligned-stack base address register.
   unsigned AP = 0;
   if (const MachineInstr *AI = getAlignaInstr(MF))
     AP = AI->getOperand(0).getReg();
   auto &HMFI = *MF.getInfo<HexagonMachineFunctionInfo>();
   HMFI.setStackAlignBasePhysReg(AP);

llvm/lib/Target/NVPTX/NVPTXPrologEpilogPass.cpp

NVPTXPrologEpilogPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
 
   // No scavenger
 
   // FIXME: Once this is working, then enable flag will change to a target
   // check for whether the frame is large enough to want to use virtual
   // frame index registers. Functions which don't want/need this optimization
   // will continue to use the existing code path.
   if (MFI.getUseLocalStackAllocationBlock()) {
-    unsigned Align = MFI.getLocalFrameMaxAlign();
+    unsigned Align = MFI.getLocalFrameMaxAlign().value();
 
     // Adjust to alignment boundary.
     Offset = (Offset + Align - 1) / Align * Align;
 
     LLVM_DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
 
     // Resolve offsets for objects in the local block.
     for (unsigned i = 0, e = MFI.getLocalFrameObjectCount(); i != e; ++i) {