[PM/AA] Rebuild LLVM's alias analysis infrastructure in a way compatible

with the new pass manager, and no longer relying on analysis groups.

This builds essentially a ground-up new AA infrastructure stack for
LLVM. The core ideas are the same that are used throughout the new pass
manager: type erased polymorphism and direct composition. The design is
as follows:

- FunctionAAResults is a type-erasing alias analysis results aggregation
  interface to walk a single query across a range of results from
  different alias analyses. Currently this is function-specific as we
  always assume that aliasing queries are *within* a function.

- AAResultBase is a CRTP utility providing stub implementations of
  various parts of the alias analysis result concept, notably in several
  cases in terms of other more general parts of the interface. This can
  be used to implement only a narrow part of the interface rather than
  the entire interface. This isn't really ideal, this logic should be
  hoisted into FunctionAAResults as currently it will cause
  a significant amount of redundant work, but it faithfully models the
  behavior of the prior infrastructure.

- All the alias analysis passes are ported to be wrapper passes for the
  legacy PM and new-style analysis passes for the new PM with a shared
  result object. In some cases (most notably CFL), this is an extremely
  naive approach that we should revisit when we can specialize for the
  new pass manager.

- BasicAA has been restructured to reflect that it is much more
  fundamentally a function analysis because it uses dominator trees and
  loop info that need to be constructed for each function.

All of the references to getting alias analysis results have been
updated to use the new aggregation interface. All the preservation and
other pass management code has been updated accordingly.

The way the FunctionAAResultsWrapperPass works is to detect the
available alias analyses when run, and add them to the results object.
This means that we should be able to continue to respect when various
passes are added to the pipeline, for example adding CFL or adding TBAA
passes should just cause their results to be available and to get folded
into this. The exception to this rule is BasicAA which really needs to
be a function pass due to using dominator trees and loop info. As
a consequence, the FunctionAAResultsWrapperPass directly depends on
BasicAA and always includes it in the aggregation.

This has significant implications for preserving analyses. Generally,
most passes shouldn't bother preserving FunctionAAResultsWrapperPass
because rebuilding the results just updates the set of known AA passes.
The exception to this rule are LoopPass instances which need to preserve
all the function analyses that the loop pass manager will end up
needing. This means preserving both BasicAAWrapperPass and the
aggregating FunctionAAResultsWrapperPass.

Now, when preserving an alias analysis, you do so by directly preserving
that analysis. This is only necessary for non-immutable-pass-provided
alias analyses though, and there are only three of interest: BasicAA,
GlobalsAA (formerly GlobalsModRef), and SCEVAA. Usually BasicAA is
preserved when needed because it (like DominatorTree and LoopInfo) is
marked as a CFG-only pass. I've expanded GlobalsAA into the preserved
set everywhere we previously were preserving all of AliasAnalysis, and
I've added SCEVAA in the intersection of that with where we preserve
SCEV itself.

One significant challenge to all of this is that the CGSCC passes were
actually using the alias analysis implementations by taking advantage of
a pretty amazing set of loop holes in the old pass manager's analysis
management code which allowed analysis groups to slide through in many
cases. Moving away from analysis groups makes this problem much more
obvious. To fix it, I've leveraged the flexibility the design of the new
PM components provides to just directly construct the relevant alias
analyses for the relevant functions in the IPO passes that need them.
This is a bit hacky, but should go away with the new pass manager, and
is already in many ways cleaner than the prior state.

Another significant challenge is that various facilities of the old
alias analysis infrastructure just don't fit any more. The most
significant of these is the alias analysis 'counter' pass. That pass
relied on the ability to snoop on AA queries at different points in the
analysis group chain. Instead, I'm planning to build printing
functionality directly into the aggregation layer. I've not included
that in this patch merely to keep it smaller.

Note that all of this needs a nearly complete rewrite of the AA
documentation. I'm planning to do that, but I'd like to make sure the
new design settles, and to flesh out a bit more of what it looks like in
the new pass manager first.

Differential Revision: http://reviews.llvm.org/D12080

llvm-svn: 247167

1 files changed, 56 insertions, 51 deletions

diff --git a/llvm/lib/Analysis/CFLAliasAnalysis.cpp b/llvm/lib/Analysis/CFLAliasAnalysis.cpp
index 729f7e412a8..4843ed6587a 100644
--- a/llvm/lib/Analysis/CFLAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/CFLAliasAnalysis.cpp
@@ -33,7 +33,7 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
-#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/InstVisitor.h"
@@ -53,18 +53,11 @@ using namespace llvm;
 
 #define DEBUG_TYPE "cfl-aa"
 
-// -- Setting up/registering CFLAA pass -- //
-char CFLAliasAnalysis::ID = 0;
-
-INITIALIZE_AG_PASS(CFLAliasAnalysis, AliasAnalysis, "cfl-aa",
-                   "CFL-Based AA implementation", false, true, false)
-
-ImmutablePass *llvm::createCFLAliasAnalysisPass() {
-  return new CFLAliasAnalysis();
-}
+CFLAAResult::CFLAAResult(const TargetLibraryInfo &TLI) : AAResultBase(TLI) {}
+CFLAAResult::CFLAAResult(CFLAAResult &&Arg) : AAResultBase(std::move(Arg)) {}
 
 // \brief Information we have about a function and would like to keep around
-struct CFLAliasAnalysis::FunctionInfo {
+struct CFLAAResult::FunctionInfo {
   StratifiedSets<Value *> Sets;
   // Lots of functions have < 4 returns. Adjust as necessary.
   SmallVector<Value *, 4> ReturnedValues;
@@ -73,22 +66,6 @@ struct CFLAliasAnalysis::FunctionInfo {
       : Sets(std::move(S)), ReturnedValues(std::move(RV)) {}
 };
 
-CFLAliasAnalysis::CFLAliasAnalysis() : ImmutablePass(ID) {
-  initializeCFLAliasAnalysisPass(*PassRegistry::getPassRegistry());
-}
-
-CFLAliasAnalysis::~CFLAliasAnalysis() {}
-
-void CFLAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
-  AliasAnalysis::getAnalysisUsage(AU);
-}
-
-void *CFLAliasAnalysis::getAdjustedAnalysisPointer(const void *ID) {
-  if (ID == &AliasAnalysis::ID)
-    return (AliasAnalysis *)this;
-  return this;
-}
-
 // Try to go from a Value* to a Function*. Never returns nullptr.
 static Optional<Function *> parentFunctionOfValue(Value *);
 
@@ -177,11 +154,11 @@ struct Edge {
 
 // \brief Gets the edges our graph should have, based on an Instruction*
 class GetEdgesVisitor : public InstVisitor<GetEdgesVisitor, void> {
-  CFLAliasAnalysis &AA;
+  CFLAAResult &AA;
   SmallVectorImpl<Edge> &Output;
 
 public:
-  GetEdgesVisitor(CFLAliasAnalysis &AA, SmallVectorImpl<Edge> &Output)
+  GetEdgesVisitor(CFLAAResult &AA, SmallVectorImpl<Edge> &Output)
       : AA(AA), Output(Output) {}
 
   void visitInstruction(Instruction &) {
@@ -669,12 +646,10 @@ static Optional<StratifiedAttr> valueToAttrIndex(Value *Val);
 static EdgeType flipWeight(EdgeType);
 
 // Gets edges of the given Instruction*, writing them to the SmallVector*.
-static void argsToEdges(CFLAliasAnalysis &, Instruction *,
-                        SmallVectorImpl<Edge> &);
+static void argsToEdges(CFLAAResult &, Instruction *, SmallVectorImpl<Edge> &);
 
 // Gets edges of the given ConstantExpr*, writing them to the SmallVector*.
-static void argsToEdges(CFLAliasAnalysis &, ConstantExpr *,
-                        SmallVectorImpl<Edge> &);
+static void argsToEdges(CFLAAResult &, ConstantExpr *, SmallVectorImpl<Edge> &);
 
 // Gets the "Level" that one should travel in StratifiedSets
 // given an EdgeType.
@@ -682,13 +657,13 @@ static Level directionOfEdgeType(EdgeType);
 
 // Builds the graph needed for constructing the StratifiedSets for the
 // given function
-static void buildGraphFrom(CFLAliasAnalysis &, Function *,
+static void buildGraphFrom(CFLAAResult &, Function *,
                            SmallVectorImpl<Value *> &, NodeMapT &, GraphT &);
 
 // Gets the edges of a ConstantExpr as if it was an Instruction. This
 // function also acts on any nested ConstantExprs, adding the edges
 // of those to the given SmallVector as well.
-static void constexprToEdges(CFLAliasAnalysis &, ConstantExpr &,
+static void constexprToEdges(CFLAAResult &, ConstantExpr &,
                              SmallVectorImpl<Edge> &);
 
 // Given an Instruction, this will add it to the graph, along with any
@@ -697,7 +672,7 @@ static void constexprToEdges(CFLAliasAnalysis &, ConstantExpr &,
 //   %0 = load i16* getelementptr ([1 x i16]* @a, 0, 0), align 2
 // addInstructionToGraph would add both the `load` and `getelementptr`
 // instructions to the graph appropriately.
-static void addInstructionToGraph(CFLAliasAnalysis &, Instruction &,
+static void addInstructionToGraph(CFLAAResult &, Instruction &,
                                   SmallVectorImpl<Value *> &, NodeMapT &,
                                   GraphT &);
 
@@ -777,7 +752,7 @@ static EdgeType flipWeight(EdgeType Initial) {
   llvm_unreachable("Incomplete coverage of EdgeType enum");
 }
 
-static void argsToEdges(CFLAliasAnalysis &Analysis, Instruction *Inst,
+static void argsToEdges(CFLAAResult &Analysis, Instruction *Inst,
                         SmallVectorImpl<Edge> &Output) {
   assert(hasUsefulEdges(Inst) &&
          "Expected instructions to have 'useful' edges");
@@ -785,7 +760,7 @@ static void argsToEdges(CFLAliasAnalysis &Analysis, Instruction *Inst,
   v.visit(Inst);
 }
 
-static void argsToEdges(CFLAliasAnalysis &Analysis, ConstantExpr *CE,
+static void argsToEdges(CFLAAResult &Analysis, ConstantExpr *CE,
                         SmallVectorImpl<Edge> &Output) {
   assert(hasUsefulEdges(CE) && "Expected constant expr to have 'useful' edges");
   GetEdgesVisitor v(Analysis, Output);
@@ -804,7 +779,7 @@ static Level directionOfEdgeType(EdgeType Weight) {
   llvm_unreachable("Incomplete switch coverage");
 }
 
-static void constexprToEdges(CFLAliasAnalysis &Analysis,
+static void constexprToEdges(CFLAAResult &Analysis,
                              ConstantExpr &CExprToCollapse,
                              SmallVectorImpl<Edge> &Results) {
   SmallVector<ConstantExpr *, 4> Worklist;
@@ -834,7 +809,7 @@ static void constexprToEdges(CFLAliasAnalysis &Analysis,
   }
 }
 
-static void addInstructionToGraph(CFLAliasAnalysis &Analysis, Instruction &Inst,
+static void addInstructionToGraph(CFLAAResult &Analysis, Instruction &Inst,
                                   SmallVectorImpl<Value *> &ReturnedValues,
                                   NodeMapT &Map, GraphT &Graph) {
   const auto findOrInsertNode = [&Map, &Graph](Value *Val) {
@@ -897,7 +872,7 @@ static void addInstructionToGraph(CFLAliasAnalysis &Analysis, Instruction &Inst,
 // buy us much that we don't already have. I'd like to add interprocedural
 // analysis prior to this however, in case that somehow requires the graph
 // produced by this for efficient execution
-static void buildGraphFrom(CFLAliasAnalysis &Analysis, Function *Fn,
+static void buildGraphFrom(CFLAAResult &Analysis, Function *Fn,
                            SmallVectorImpl<Value *> &ReturnedValues,
                            NodeMapT &Map, GraphT &Graph) {
   for (auto &Bb : Fn->getBasicBlockList())
@@ -928,7 +903,7 @@ static bool canSkipAddingToSets(Value *Val) {
 }
 
 // Builds the graph + StratifiedSets for a function.
-CFLAliasAnalysis::FunctionInfo CFLAliasAnalysis::buildSetsFrom(Function *Fn) {
+CFLAAResult::FunctionInfo CFLAAResult::buildSetsFrom(Function *Fn) {
   NodeMapT Map;
   GraphT Graph;
   SmallVector<Value *, 4> ReturnedValues;
@@ -1014,7 +989,7 @@ CFLAliasAnalysis::FunctionInfo CFLAliasAnalysis::buildSetsFrom(Function *Fn) {
   return FunctionInfo(Builder.build(), std::move(ReturnedValues));
 }
 
-void CFLAliasAnalysis::scan(Function *Fn) {
+void CFLAAResult::scan(Function *Fn) {
   auto InsertPair = Cache.insert(std::make_pair(Fn, Optional<FunctionInfo>()));
   (void)InsertPair;
   assert(InsertPair.second &&
@@ -1025,12 +1000,12 @@ void CFLAliasAnalysis::scan(Function *Fn) {
   Handles.push_front(FunctionHandle(Fn, this));
 }
 
-void CFLAliasAnalysis::evict(Function *Fn) { Cache.erase(Fn); }
+void CFLAAResult::evict(Function *Fn) { Cache.erase(Fn); }
 
 /// \brief Ensures that the given function is available in the cache.
 /// Returns the appropriate entry from the cache.
-const Optional<CFLAliasAnalysis::FunctionInfo> &
-CFLAliasAnalysis::ensureCached(Function *Fn) {
+const Optional<CFLAAResult::FunctionInfo> &
+CFLAAResult::ensureCached(Function *Fn) {
   auto Iter = Cache.find(Fn);
   if (Iter == Cache.end()) {
     scan(Fn);
@@ -1041,8 +1016,8 @@ CFLAliasAnalysis::ensureCached(Function *Fn) {
   return Iter->second;
 }
 
-AliasResult CFLAliasAnalysis::query(const MemoryLocation &LocA,
-                                    const MemoryLocation &LocB) {
+AliasResult CFLAAResult::query(const MemoryLocation &LocA,
+                               const MemoryLocation &LocB) {
   auto *ValA = const_cast<Value *>(LocA.Ptr);
   auto *ValB = const_cast<Value *>(LocB.Ptr);
 
@@ -1108,7 +1083,37 @@ AliasResult CFLAliasAnalysis::query(const MemoryLocation &LocA,
   return NoAlias;
 }
 
-bool CFLAliasAnalysis::doInitialization(Module &M) {
-  InitializeAliasAnalysis(this, &M.getDataLayout());
-  return true;
+CFLAAResult CFLAA::run(Function &F, AnalysisManager<Function> *AM) {
+  return CFLAAResult(AM->getResult<TargetLibraryAnalysis>(F));
+}
+
+char CFLAA::PassID;
+
+char CFLAAWrapperPass::ID = 0;
+INITIALIZE_PASS_BEGIN(CFLAAWrapperPass, "cfl-aa", "CFL-Based Alias Analysis",
+                      false, true)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
+INITIALIZE_PASS_END(CFLAAWrapperPass, "cfl-aa", "CFL-Based Alias Analysis",
+                    false, true)
+
+ImmutablePass *llvm::createCFLAAWrapperPass() { return new CFLAAWrapperPass(); }
+
+CFLAAWrapperPass::CFLAAWrapperPass() : ImmutablePass(ID) {
+  initializeCFLAAWrapperPassPass(*PassRegistry::getPassRegistry());
+}
+
+bool CFLAAWrapperPass::doInitialization(Module &M) {
+  Result.reset(
+      new CFLAAResult(getAnalysis<TargetLibraryInfoWrapperPass>().getTLI()));
+  return false;
+}
+
+bool CFLAAWrapperPass::doFinalization(Module &M) {
+  Result.reset();
+  return false;
+}
+
+void CFLAAWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.setPreservesAll();
+  AU.addRequired<TargetLibraryInfoWrapperPass>();
 }