[LLVM][Alignment] Make functions using log of alignment explicit

Summary:
This patch renames functions that takes or returns alignment as log2, this patch will help with the transition to llvm::Align.
The renaming makes it explicit that we deal with log(alignment) instead of a power of two alignment.
A few renames uncovered dubious assignments:

 - `MirParser`/`MirPrinter` was expecting powers of two but `MachineFunction` and `MachineBasicBlock` were using deal with log2(align). This patch fixes it and updates the documentation.
 - `MachineBlockPlacement` exposes two flags (`align-all-blocks` and `align-all-nofallthru-blocks`) supposedly interpreted as power of two alignments, internally these values are interpreted as log2(align). This patch updates the documentation,
 - `MachineFunctionexposes` exposes `align-all-functions` also interpreted as power of two alignment, internally this value is interpreted as log2(align). This patch updates the documentation,

Reviewers: lattner, thegameg, courbet

Subscribers: dschuff, arsenm, jyknight, dylanmckay, sdardis, nemanjai, jvesely, nhaehnle, javed.absar, hiraditya, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, dexonsmith, PkmX, jocewei, jsji, Jim, s.egerton, llvm-commits, courbet

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65945

llvm-svn: 371045

11 files changed, 47 insertions, 44 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 220c4758956..bf0be8ecee9 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -667,7 +667,7 @@ void AsmPrinter::EmitFunctionHeader() {
 
   EmitLinkage(&F, CurrentFnSym);
   if (MAI->hasFunctionAlignment())
-    EmitAlignment(MF->getAlignment(), &F);
+    EmitAlignment(MF->getLogAlignment(), &F);
 
   if (MAI->hasDotTypeDotSizeDirective())
     OutStreamer->EmitSymbolAttribute(CurrentFnSym, MCSA_ELF_TypeFunction);
@@ -2905,8 +2905,8 @@ void AsmPrinter::EmitBasicBlockStart(const MachineBasicBlock &MBB) {
   }
 
   // Emit an alignment directive for this block, if needed.
-  if (unsigned Align = MBB.getAlignment())
-    EmitAlignment(Align);
+  if (unsigned LogAlign = MBB.getLogAlignment())
+    EmitAlignment(LogAlign);
   MCCodePaddingContext Context;
   setupCodePaddingContext(MBB, Context);
   OutStreamer->EmitCodePaddingBasicBlockStart(Context);
diff --git a/llvm/lib/CodeGen/AsmPrinter/WinException.cpp b/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
index 155e91ce61a..ef5aa0499e1 100644
--- a/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/WinException.cpp
@@ -203,8 +203,8 @@ void WinException::beginFunclet(const MachineBasicBlock &MBB,
 
     // We want our funclet's entry point to be aligned such that no nops will be
     // present after the label.
-    Asm->EmitAlignment(std::max(Asm->MF->getAlignment(), MBB.getAlignment()),
-                       &F);
+    Asm->EmitAlignment(
+        std::max(Asm->MF->getLogAlignment(), MBB.getLogAlignment()), &F);
 
     // Now that we've emitted the alignment directive, point at our funclet.
     Asm->OutStreamer->EmitLabel(Sym);
diff --git a/llvm/lib/CodeGen/BranchRelaxation.cpp b/llvm/lib/CodeGen/BranchRelaxation.cpp
index 55fbf0163dd..4ee61cff4b4 100644
--- a/llvm/lib/CodeGen/BranchRelaxation.cpp
+++ b/llvm/lib/CodeGen/BranchRelaxation.cpp
@@ -65,13 +65,13 @@ class BranchRelaxation : public MachineFunctionPass {
     /// block.
     unsigned postOffset(const MachineBasicBlock &MBB) const {
       unsigned PO = Offset + Size;
-      unsigned Align = MBB.getAlignment();
-      if (Align == 0)
+      unsigned LogAlign = MBB.getLogAlignment();
+      if (LogAlign == 0)
         return PO;
 
-      unsigned AlignAmt = 1 << Align;
-      unsigned ParentAlign = MBB.getParent()->getAlignment();
-      if (Align <= ParentAlign)
+      unsigned AlignAmt = 1 << LogAlign;
+      unsigned ParentLogAlign = MBB.getParent()->getLogAlignment();
+      if (LogAlign <= ParentLogAlign)
         return PO + OffsetToAlignment(PO, AlignAmt);
 
       // The alignment of this MBB is larger than the function's alignment, so we
@@ -128,9 +128,9 @@ void BranchRelaxation::verify() {
 #ifndef NDEBUG
   unsigned PrevNum = MF->begin()->getNumber();
   for (MachineBasicBlock &MBB : *MF) {
-    unsigned Align = MBB.getAlignment();
+    unsigned LogAlign = MBB.getLogAlignment();
     unsigned Num = MBB.getNumber();
-    assert(BlockInfo[Num].Offset % (1u << Align) == 0);
+    assert(BlockInfo[Num].Offset % (1u << LogAlign) == 0);
     assert(!Num || BlockInfo[PrevNum].postOffset(MBB) <= BlockInfo[Num].Offset);
     assert(BlockInfo[Num].Size == computeBlockSize(MBB));
     PrevNum = Num;
diff --git a/llvm/lib/CodeGen/MIRParser/MIParser.cpp b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
index a8fa2f1195d..f8c4dd66559 100644
--- a/llvm/lib/CodeGen/MIRParser/MIParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIParser.cpp
@@ -641,7 +641,7 @@ bool MIParser::parseBasicBlockDefinition(
     return error(Loc, Twine("redefinition of machine basic block with id #") +
                           Twine(ID));
   if (Alignment)
-    MBB->setAlignment(Alignment);
+    MBB->setLogAlignment(Log2_32(Alignment));
   if (HasAddressTaken)
     MBB->setHasAddressTaken();
   MBB->setIsEHPad(IsLandingPad);
diff --git a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
index 48ec0b2d6cf..2dd4fd3b9b7 100644
--- a/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
+++ b/llvm/lib/CodeGen/MIRParser/MIRParser.cpp
@@ -393,7 +393,7 @@ MIRParserImpl::initializeMachineFunction(const yaml::MachineFunction &YamlMF,
   }
 
   if (YamlMF.Alignment)
-    MF.setAlignment(YamlMF.Alignment);
+    MF.setLogAlignment(Log2_32(YamlMF.Alignment));
   MF.setExposesReturnsTwice(YamlMF.ExposesReturnsTwice);
   MF.setHasWinCFI(YamlMF.HasWinCFI);
 
diff --git a/llvm/lib/CodeGen/MIRPrinter.cpp b/llvm/lib/CodeGen/MIRPrinter.cpp
index 7febb11dcb8..18efe1f80eb 100644
--- a/llvm/lib/CodeGen/MIRPrinter.cpp
+++ b/llvm/lib/CodeGen/MIRPrinter.cpp
@@ -197,7 +197,7 @@ void MIRPrinter::print(const MachineFunction &MF) {
 
   yaml::MachineFunction YamlMF;
   YamlMF.Name = MF.getName();
-  YamlMF.Alignment = MF.getAlignment();
+  YamlMF.Alignment = 1UL << MF.getLogAlignment();
   YamlMF.ExposesReturnsTwice = MF.exposesReturnsTwice();
   YamlMF.HasWinCFI = MF.hasWinCFI();
 
@@ -629,9 +629,10 @@ void MIPrinter::print(const MachineBasicBlock &MBB) {
     OS << "landing-pad";
     HasAttributes = true;
   }
-  if (MBB.getAlignment()) {
+  if (MBB.getLogAlignment()) {
     OS << (HasAttributes ? ", " : " (");
-    OS << "align " << MBB.getAlignment();
+    OS << "align "
+       << (1UL << MBB.getLogAlignment());
     HasAttributes = true;
   }
   if (HasAttributes)
diff --git a/llvm/lib/CodeGen/MachineBasicBlock.cpp b/llvm/lib/CodeGen/MachineBasicBlock.cpp
index 050934daa5a..bd2ab45f669 100644
--- a/llvm/lib/CodeGen/MachineBasicBlock.cpp
+++ b/llvm/lib/CodeGen/MachineBasicBlock.cpp
@@ -326,9 +326,9 @@ void MachineBasicBlock::print(raw_ostream &OS, ModuleSlotTracker &MST,
     OS << "landing-pad";
     HasAttributes = true;
   }
-  if (getAlignment()) {
+  if (getLogAlignment()) {
     OS << (HasAttributes ? ", " : " (");
-    OS << "align " << getAlignment();
+    OS << "align " << getLogAlignment();
     HasAttributes = true;
   }
   if (HasAttributes)
diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index 641f14d617c..f2a64faab2e 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -79,16 +79,17 @@ STATISTIC(CondBranchTakenFreq,
 STATISTIC(UncondBranchTakenFreq,
           "Potential frequency of taking unconditional branches");
 
-static cl::opt<unsigned> AlignAllBlock("align-all-blocks",
-                                       cl::desc("Force the alignment of all "
-                                                "blocks in the function."),
-                                       cl::init(0), cl::Hidden);
+static cl::opt<unsigned> AlignAllBlock(
+    "align-all-blocks",
+    cl::desc("Force the alignment of all blocks in the function in log2 format "
+             "(e.g 4 means align on 16B boundaries)."),
+    cl::init(0), cl::Hidden);
 
 static cl::opt<unsigned> AlignAllNonFallThruBlocks(
     "align-all-nofallthru-blocks",
-    cl::desc("Force the alignment of all "
-             "blocks that have no fall-through predecessors (i.e. don't add "
-             "nops that are executed)."),
+    cl::desc("Force the alignment of all blocks that have no fall-through "
+             "predecessors (i.e. don't add nops that are executed). In log2 "
+             "format (e.g 4 means align on 16B boundaries)."),
     cl::init(0), cl::Hidden);
 
 // FIXME: Find a good default for this flag and remove the flag.
@@ -2763,8 +2764,8 @@ void MachineBlockPlacement::alignBlocks() {
     if (!L)
       continue;
 
-    unsigned Align = TLI->getPrefLoopAlignment(L);
-    if (!Align)
+    unsigned LogAlign = TLI->getPrefLoopLogAlignment(L);
+    if (!LogAlign)
       continue; // Don't care about loop alignment.
 
     // If the block is cold relative to the function entry don't waste space
@@ -2788,7 +2789,7 @@ void MachineBlockPlacement::alignBlocks() {
     // Force alignment if all the predecessors are jumps. We already checked
     // that the block isn't cold above.
     if (!LayoutPred->isSuccessor(ChainBB)) {
-      ChainBB->setAlignment(Align);
+      ChainBB->setLogAlignment(LogAlign);
       continue;
     }
 
@@ -2800,7 +2801,7 @@ void MachineBlockPlacement::alignBlocks() {
         MBPI->getEdgeProbability(LayoutPred, ChainBB);
     BlockFrequency LayoutEdgeFreq = MBFI->getBlockFreq(LayoutPred) * LayoutProb;
     if (LayoutEdgeFreq <= (Freq * ColdProb))
-      ChainBB->setAlignment(Align);
+      ChainBB->setLogAlignment(LogAlign);
   }
 }
 
@@ -3062,14 +3063,14 @@ bool MachineBlockPlacement::runOnMachineFunction(MachineFunction &MF) {
   if (AlignAllBlock)
     // Align all of the blocks in the function to a specific alignment.
     for (MachineBasicBlock &MBB : MF)
-      MBB.setAlignment(AlignAllBlock);
+      MBB.setLogAlignment(AlignAllBlock);
   else if (AlignAllNonFallThruBlocks) {
     // Align all of the blocks that have no fall-through predecessors to a
     // specific alignment.
     for (auto MBI = std::next(MF.begin()), MBE = MF.end(); MBI != MBE; ++MBI) {
       auto LayoutPred = std::prev(MBI);
       if (!LayoutPred->isSuccessor(&*MBI))
-        MBI->setAlignment(AlignAllNonFallThruBlocks);
+        MBI->setLogAlignment(AlignAllNonFallThruBlocks);
     }
   }
   if (ViewBlockLayoutWithBFI != GVDT_None &&
diff --git a/llvm/lib/CodeGen/MachineFunction.cpp b/llvm/lib/CodeGen/MachineFunction.cpp
index b771dd1a351..d136ebd437f 100644
--- a/llvm/lib/CodeGen/MachineFunction.cpp
+++ b/llvm/lib/CodeGen/MachineFunction.cpp
@@ -78,10 +78,11 @@ using namespace llvm;
 
 #define DEBUG_TYPE "codegen"
 
-static cl::opt<unsigned>
-AlignAllFunctions("align-all-functions",
-                  cl::desc("Force the alignment of all functions."),
-                  cl::init(0), cl::Hidden);
+static cl::opt<unsigned> AlignAllFunctions(
+    "align-all-functions",
+    cl::desc("Force the alignment of all functions in log2 format (e.g. 4 "
+             "means align on 16B boundaries)."),
+    cl::init(0), cl::Hidden);
 
 static const char *getPropertyName(MachineFunctionProperties::Property Prop) {
   using P = MachineFunctionProperties::Property;
@@ -172,16 +173,16 @@ void MachineFunction::init() {
     FrameInfo->ensureMaxAlignment(F.getFnStackAlignment());
 
   ConstantPool = new (Allocator) MachineConstantPool(getDataLayout());
-  Alignment = STI->getTargetLowering()->getMinFunctionAlignment();
+  LogAlignment = STI->getTargetLowering()->getMinFunctionLogAlignment();
 
   // FIXME: Shouldn't use pref alignment if explicit alignment is set on F.
   // FIXME: Use Function::hasOptSize().
   if (!F.hasFnAttribute(Attribute::OptimizeForSize))
-    Alignment = std::max(Alignment,
-                         STI->getTargetLowering()->getPrefFunctionAlignment());
+    LogAlignment = std::max(
+        LogAlignment, STI->getTargetLowering()->getPrefFunctionLogAlignment());
 
   if (AlignAllFunctions)
-    Alignment = AlignAllFunctions;
+    LogAlignment = AlignAllFunctions;
 
   JumpTableInfo = nullptr;
 
diff --git a/llvm/lib/CodeGen/PatchableFunction.cpp b/llvm/lib/CodeGen/PatchableFunction.cpp
index a3fa1b0ad8e..07f88597fe6 100644
--- a/llvm/lib/CodeGen/PatchableFunction.cpp
+++ b/llvm/lib/CodeGen/PatchableFunction.cpp
@@ -78,7 +78,7 @@ bool PatchableFunction::runOnMachineFunction(MachineFunction &MF) {
     MIB.add(MO);
 
   FirstActualI->eraseFromParent();
-  MF.ensureAlignment(4);
+  MF.ensureLogAlignment(4);
   return true;
 }
 
diff --git a/llvm/lib/CodeGen/TargetLoweringBase.cpp b/llvm/lib/CodeGen/TargetLoweringBase.cpp
index e9a7d4b5252..970b2067d42 100644
--- a/llvm/lib/CodeGen/TargetLoweringBase.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringBase.cpp
@@ -583,9 +583,9 @@ TargetLoweringBase::TargetLoweringBase(const TargetMachine &tm) : TM(tm) {
   BooleanFloatContents = UndefinedBooleanContent;
   BooleanVectorContents = UndefinedBooleanContent;
   SchedPreferenceInfo = Sched::ILP;
-  MinFunctionAlignment = 0;
-  PrefFunctionAlignment = 0;
-  PrefLoopAlignment = 0;
+  MinFunctionLogAlignment = 0;
+  PrefFunctionLogAlignment = 0;
+  PrefLoopLogAlignment = 0;
   GatherAllAliasesMaxDepth = 18;
   MinStackArgumentAlignment = 1;
   // TODO: the default will be switched to 0 in the next commit, along