[LLVM][Alignment] Introduce Alignment Type in DataLayout

[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

[jfb]

llvm/include/llvm/IR/DataLayout.h

269

Return MaybeAlign here? Or in a future patch?

275

Ditto.

[gchatelet]

llvm/include/llvm/IR/DataLayout.h

269

Touching interfaces of widely used types is very contaminating and pulling the string leads to huge patches that are hard to review.
My rough plan is the following:

• Change the implementation details of the widely used types but don't touch the interface if it triggers too much changes
• Change the leaves implementations, e.g. llvm/lib/Target/XXX. The changes here should be self contained.
• Change interfaces of widely used types, one interface at a time.

I'll have a look at what it takes to include it in this patch and report back.

[gchatelet]

• Make getFunctionPtrAlign() return MaybeAlign

[gchatelet]

Also changed getFunctionPtrAlign() return type to MaybeAlign.
Keeping getStackAlignment() return type as unsigned for now.

llvm/include/llvm/IR/DataLayout.h

 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Type.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Support/Alignment.h"
 #include <cassert>
 #include <cstdint>
 #include <string>
 
 // This needs to be outside of the namespace, to avoid conflict with llvm-c
 // decl.
 using LLVMTargetDataRef = struct LLVMOpaqueTargetData *;
 
enum class FunctionPtrAlignType {
     /// The function pointer alignment is a multiple of the function alignment.
     MultipleOfFunctionAlign,
   };
 private:
   /// Defaults to false.
   bool BigEndian;
 
   unsigned AllocaAddrSpace;
-  unsigned StackNaturalAlign;
+  MaybeAlign StackNaturalAlign;
   unsigned ProgramAddrSpace;
 
-  unsigned FunctionPtrAlign;
+  MaybeAlign FunctionPtrAlign;
   FunctionPtrAlignType TheFunctionPtrAlignType;
 
   enum ManglingModeT {
     MM_None,
     MM_ELF,
     MM_MachO,
     MM_WinCOFF,
     MM_WinCOFFX86,
for (unsigned LegalIntWidth : LegalIntWidths)
       if (LegalIntWidth == Width)
         return true;
     return false;
   }
 
   bool isIllegalInteger(uint64_t Width) const { return !isLegalInteger(Width); }
 
   /// Returns true if the given alignment exceeds the natural stack alignment.
-  bool exceedsNaturalStackAlignment(unsigned Align) const {
-    return (StackNaturalAlign != 0) && (Align > StackNaturalAlign);
+  bool exceedsNaturalStackAlignment(llvm::Align Align) const {
+    return StackNaturalAlign && (Align > StackNaturalAlign);
   }
 
-  unsigned getStackAlignment() const { return StackNaturalAlign; }
+  unsigned getStackAlignment() const { return StackNaturalAlign ? StackNaturalAlign->value() : 0; }
   unsigned getAllocaAddrSpace() const { return AllocaAddrSpace; }
 
   /// Returns the alignment of function pointers, which may or may not be
   /// related to the alignment of functions.
   /// \see getFunctionPtrAlignType
-  unsigned getFunctionPtrAlign() const { return FunctionPtrAlign; }
+  MaybeAlign getFunctionPtrAlign() const { return FunctionPtrAlign; }
 
   /// Return the type of function pointer alignment.
   /// \see getFunctionPtrAlign
   FunctionPtrAlignType getFunctionPtrAlignType() const {
     return TheFunctionPtrAlignType;
   }
 
   unsigned getProgramAddressSpace() const { return ProgramAddrSpace; }

llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

if (DstAlignCanChange) {
     Type *IRTy = getTypeForLLT(MemOps[0], C);
     unsigned NewAlign = (unsigned)DL.getABITypeAlignment(IRTy);
 
     // Don't promote to an alignment that would require dynamic stack
     // realignment.
     const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
     if (!TRI->needsStackRealignment(MF))
       while (NewAlign > Align &&
-             DL.exceedsNaturalStackAlignment(NewAlign))
+             DL.exceedsNaturalStackAlignment(llvm::Align(NewAlign)))
           NewAlign /= 2;
 
     if (NewAlign > Align) {
       unsigned FI = FIDef->getOperand(1).getIndex();
       // Give the stack frame object a larger alignment if needed.
       if (MFI.getObjectAlignment(FI) < NewAlign)
         MFI.setObjectAlignment(FI, NewAlign);
       Align = NewAlign;
if (DstAlignCanChange) {
     Type *IRTy = getTypeForLLT(MemOps[0], C);
     unsigned NewAlign = (unsigned)DL.getABITypeAlignment(IRTy);
 
     // Don't promote to an alignment that would require dynamic stack
     // realignment.
     const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
     if (!TRI->needsStackRealignment(MF))
       while (NewAlign > Align &&
-             DL.exceedsNaturalStackAlignment(NewAlign))
+             DL.exceedsNaturalStackAlignment(llvm::Align(NewAlign)))
           NewAlign /= 2;
 
     if (NewAlign > Align) {
       unsigned FI = FIDef->getOperand(1).getIndex();
       // Give the stack frame object a larger alignment if needed.
       if (MFI.getObjectAlignment(FI) < NewAlign)
         MFI.setObjectAlignment(FI, NewAlign);
       Align = NewAlign;

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

if (DstAlignCanChange) {
     Type *Ty = MemOps[0].getTypeForEVT(C);
     unsigned NewAlign = (unsigned)DL.getABITypeAlignment(Ty);
 
     // Don't promote to an alignment that would require dynamic stack
     // realignment.
     const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
     if (!TRI->needsStackRealignment(MF))
       while (NewAlign > Align &&
-             DL.exceedsNaturalStackAlignment(NewAlign))
+             DL.exceedsNaturalStackAlignment(llvm::Align(NewAlign)))
           NewAlign /= 2;
 
     if (NewAlign > Align) {
       // Give the stack frame object a larger alignment if needed.
       if (MFI.getObjectAlignment(FI->getIndex()) < NewAlign)
         MFI.setObjectAlignment(FI->getIndex(), NewAlign);
       Align = NewAlign;
     }

llvm/lib/IR/DataLayout.cpp

 };
 
 void DataLayout::reset(StringRef Desc) {
   clear();
 
   LayoutMap = nullptr;
   BigEndian = false;
   AllocaAddrSpace = 0;
-  StackNaturalAlign = 0;
+  StackNaturalAlign.reset();
   ProgramAddrSpace = 0;
-  FunctionPtrAlign = 0;
+  FunctionPtrAlign.reset();
   TheFunctionPtrAlignType = FunctionPtrAlignType::Independent;
   ManglingMode = MM_None;
   NonIntegralAddressSpaces.clear();
 
   // Default alignments
   for (const LayoutAlignElem &E : DefaultAlignments) {
     setAlignment((AlignTypeEnum)E.AlignType, E.ABIAlign, E.PrefAlign,
                  E.TypeBitWidth);
case 'n':  // Native integer types.
               "Zero width native integer type in datalayout string");
         LegalIntWidths.push_back(Width);
         if (Rest.empty())
           break;
         Split = split(Rest, ':');
       }
       break;
     case 'S': { // Stack natural alignment.
-      StackNaturalAlign = inBytes(getInt(Tok));
+      StackNaturalAlign = MaybeAlign(inBytes(getInt(Tok)));
       break;
     }
     case 'F': {
       switch (Tok.front()) {
       case 'i':
         TheFunctionPtrAlignType = FunctionPtrAlignType::Independent;
         break;
       case 'n':
         TheFunctionPtrAlignType = FunctionPtrAlignType::MultipleOfFunctionAlign;
         break;
       default:
         report_fatal_error("Unknown function pointer alignment type in "
                            "datalayout string");
       }
       Tok = Tok.substr(1);
-      FunctionPtrAlign = inBytes(getInt(Tok));
+      FunctionPtrAlign = MaybeAlign(inBytes(getInt(Tok)));
       break;
     }
     case 'P': { // Function address space.
       ProgramAddrSpace = getAddrSpace(Tok);
       break;
     }
     case 'A': { // Default stack/alloca address space.
       AllocaAddrSpace = getAddrSpace(Tok);

llvm/lib/IR/Value.cpp

 }
 
 unsigned Value::getPointerAlignment(const DataLayout &DL) const {
   assert(getType()->isPointerTy() && "must be pointer");
 
   unsigned Align = 0;
   if (auto *GO = dyn_cast<GlobalObject>(this)) {
     if (isa<Function>(GO)) {
+      MaybeAlign FunctionPtrAlign = DL.getFunctionPtrAlign();
+      unsigned Align = FunctionPtrAlign ? FunctionPtrAlign->value() : 0;
       switch (DL.getFunctionPtrAlignType()) {
       case DataLayout::FunctionPtrAlignType::Independent:
-        return DL.getFunctionPtrAlign();
+        return Align;
       case DataLayout::FunctionPtrAlignType::MultipleOfFunctionAlign:
-        return std::max(DL.getFunctionPtrAlign(), GO->getAlignment());
+        return std::max(Align, GO->getAlignment());
       }
     }
     Align = GO->getAlignment();
     if (Align == 0) {
       if (auto *GVar = dyn_cast<GlobalVariable>(GO)) {
         Type *ObjectType = GVar->getValueType();
         if (ObjectType->isSized()) {
           // If the object is defined in the current Module, we'll be giving

llvm/lib/Transforms/Utils/Local.cpp

if (AllocaInst *AI = dyn_cast<AllocaInst>(V)) {
     // while computeKnownBits is not allowed to traverse more than 6
     // levels.
     Align = std::max(AI->getAlignment(), Align);
     if (PrefAlign <= Align)
       return Align;
 
     // If the preferred alignment is greater than the natural stack alignment
     // then don't round up. This avoids dynamic stack realignment.
-    if (DL.exceedsNaturalStackAlignment(PrefAlign))
+    if (DL.exceedsNaturalStackAlignment(llvm::Align(PrefAlign)))
       return Align;
     AI->setAlignment(PrefAlign);
     return PrefAlign;
   }
 
   if (auto *GO = dyn_cast<GlobalObject>(V)) {
     // TODO: as above, this shouldn't be necessary.
     Align = std::max(GO->getAlignment(), Align);

llvm/unittests/IR/DataLayoutTest.cpp

 //===- ConstantRangeTest.cpp - ConstantRange tests ------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/DataLayout.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
 
 namespace {
 
 TEST(DataLayoutTest, FunctionPtrAlign) {
-  EXPECT_EQ(0U, DataLayout("").getFunctionPtrAlign());
-  EXPECT_EQ(1U, DataLayout("Fi8").getFunctionPtrAlign());
-  EXPECT_EQ(2U, DataLayout("Fi16").getFunctionPtrAlign());
-  EXPECT_EQ(4U, DataLayout("Fi32").getFunctionPtrAlign());
-  EXPECT_EQ(8U, DataLayout("Fi64").getFunctionPtrAlign());
-  EXPECT_EQ(1U, DataLayout("Fn8").getFunctionPtrAlign());
-  EXPECT_EQ(2U, DataLayout("Fn16").getFunctionPtrAlign());
-  EXPECT_EQ(4U, DataLayout("Fn32").getFunctionPtrAlign());
-  EXPECT_EQ(8U, DataLayout("Fn64").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(0), DataLayout("").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(1), DataLayout("Fi8").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(2), DataLayout("Fi16").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(4), DataLayout("Fi32").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(8), DataLayout("Fi64").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(1), DataLayout("Fn8").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(2), DataLayout("Fn16").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(4), DataLayout("Fn32").getFunctionPtrAlign());
+  EXPECT_EQ(MaybeAlign(8), DataLayout("Fn64").getFunctionPtrAlign());
   EXPECT_EQ(DataLayout::FunctionPtrAlignType::Independent, \
       DataLayout("").getFunctionPtrAlignType());
   EXPECT_EQ(DataLayout::FunctionPtrAlignType::Independent, \
       DataLayout("Fi8").getFunctionPtrAlignType());
   EXPECT_EQ(DataLayout::FunctionPtrAlignType::MultipleOfFunctionAlign, \
       DataLayout("Fn8").getFunctionPtrAlignType());
   EXPECT_EQ(DataLayout("Fi8"), DataLayout("Fi8"));
   EXPECT_NE(DataLayout("Fi8"), DataLayout("Fi16"));