[clang] nonblocking/nonallocating attributes: 2nd pass caller/callee analysis (PR #99656)

[Doug Wyatt via cfe-commits]

================
@@ -0,0 +1,1199 @@
+//=== EffectAnalysis.cpp - Sema warnings for function effects -------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements caller/callee analysis for function effects.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/AST/Decl.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/AST/Stmt.h"
+#include "clang/AST/Type.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Sema/SemaInternal.h"
+
+#define DEBUG_TYPE "fxanalysis"
+
+using namespace clang;
+
+namespace {
+
+enum class ViolationID : uint8_t {
+  None = 0, // sentinel for an empty Violation
+  Throws,
+  Catches,
+  CallsObjC,
+  AllocatesMemory,
+  HasStaticLocal,
+  AccessesThreadLocal,
+
+  // These only apply to callees, where the analysis stops at the Decl
+  DeclDisallowsInference,
+
+  CallsDeclWithoutEffect,
+  CallsExprWithoutEffect,
+};
+
+// Represents a violation of the rules, potentially for the entire duration of
+// the analysis phase, in order to refer to it when explaining why a caller has
+// been made unsafe by a callee. Can be transformed into either a Diagnostic
+// (warning or a note), depending on whether the violation pertains to a
+// function failing to be verifed as holding an effect vs. a function failing to
+// be inferred as holding that effect.
+struct Violation {
+  FunctionEffect Effect;
+  FunctionEffect CalleeEffectPreventingInference; // only for certain IDs
+  ViolationID ID = ViolationID::None;
+  SourceLocation Loc;
+  const Decl *Callee = nullptr; // only valid for Calls*
+
+  Violation() = default;
+
+  Violation(const FunctionEffect &Effect, ViolationID ID, SourceLocation Loc,
+            const Decl *Callee = nullptr,
+            const FunctionEffect *CalleeEffect = nullptr)
+      : Effect(Effect), ID(ID), Loc(Loc), Callee(Callee) {
+    if (CalleeEffect != nullptr)
+      CalleeEffectPreventingInference = *CalleeEffect;
+  }
+};
+
+enum class SpecialFuncType : uint8_t { None, OperatorNew, OperatorDelete };
+enum class CallableType {
+  // unknown: probably function pointer
+  Unknown,
+  Function,
+  Virtual,
+  Block
+};
+
+// Return whether a function's effects CAN be verified.
+// The question of whether it SHOULD be verified is independent.
+static bool functionIsVerifiable(const FunctionDecl *FD) {
+  if (FD->isTrivial()) {
+    // Otherwise `struct x { int a; };` would have an unverifiable default
+    // constructor.
+    return true;
+  }
+  return FD->hasBody();
+}
+
+static bool isNoexcept(const FunctionDecl *FD) {
+  const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
+  if (FPT->isNothrow() || FD->hasAttr<NoThrowAttr>())
+    return true;
+  return false;
+}
+
+// Transitory, more extended information about a callable, which can be a
+// function, block, or function pointer.
+struct CallableInfo {
+  // CDecl holds the function's definition, if any.
+  // FunctionDecl if CallableType::Function or Virtual
+  // BlockDecl if CallableType::Block
+  const Decl *CDecl;
+
+  // Remember whether the callable is a function, block, virtual method,
+  // or (presumed) function pointer.
+  CallableType CType = CallableType::Unknown;
+
+  // Remember whether the callable is an operator new or delete function,
+  // so that calls to them are reported more meaningfully, as memory
+  // allocations.
+  SpecialFuncType FuncType = SpecialFuncType::None;
+
+  // We inevitably want to know the callable's declared effects, so cache them.
+  FunctionEffectKindSet Effects;
+
+  CallableInfo(const Decl &CD, SpecialFuncType FT = SpecialFuncType::None)
+      : CDecl(&CD), FuncType(FT) {
+    FunctionEffectsRef DeclEffects;
+    if (auto *FD = dyn_cast<FunctionDecl>(CDecl)) {
+      // Use the function's definition, if any.
+      if (const FunctionDecl *Def = FD->getDefinition())
+        CDecl = FD = Def;
+      CType = CallableType::Function;
+      if (auto *Method = dyn_cast<CXXMethodDecl>(FD);
+          Method && Method->isVirtual())
+        CType = CallableType::Virtual;
+      DeclEffects = FD->getFunctionEffects();
+    } else if (auto *BD = dyn_cast<BlockDecl>(CDecl)) {
+      CType = CallableType::Block;
+      DeclEffects = BD->getFunctionEffects();
+    } else if (auto *VD = dyn_cast<ValueDecl>(CDecl)) {
+      // ValueDecl is function, enum, or variable, so just look at its type.
+      DeclEffects = FunctionEffectsRef::get(VD->getType());
+    }
+    Effects = FunctionEffectKindSet(DeclEffects);
+  }
+
+  CallableType type() const { return CType; }
+
+  bool isCalledDirectly() const {
+    return CType == CallableType::Function || CType == CallableType::Block;
+  }
+
+  bool isVerifiable() const {
+    switch (CType) {
+    case CallableType::Unknown:
+    case CallableType::Virtual:
+      return false;
+    case CallableType::Block:
+      return true;
+    case CallableType::Function:
+      return functionIsVerifiable(dyn_cast<FunctionDecl>(CDecl));
+    }
+    llvm_unreachable("undefined CallableType");
+  }
+
+  /// Generate a name for logging and diagnostics.
+  std::string name(Sema &Sem) const {
+    std::string Name;
+    llvm::raw_string_ostream OS(Name);
+
+    if (auto *FD = dyn_cast<FunctionDecl>(CDecl))
+      FD->getNameForDiagnostic(OS, Sem.getPrintingPolicy(),
+                               /*Qualified=*/true);
+    else if (auto *BD = dyn_cast<BlockDecl>(CDecl))
+      OS << "(block " << BD->getBlockManglingNumber() << ")";
+    else if (auto *VD = dyn_cast<NamedDecl>(CDecl))
+      VD->printQualifiedName(OS);
+    return Name;
+  }
+};
+
+// ----------
+// Map effects to single Violations, to hold the first (of potentially many)
+// violations pertaining to an effect, per function.
+class EffectToViolationMap {
+  // Since we currently only have a tiny number of effects (typically no more
+  // than 1), use a sorted SmallVector with an inline capacity of 1. Since it
+  // is often empty, use a unique_ptr to the SmallVector.
+  // Note that Violation itself contains a FunctionEffect which is the key.
+  using ImplVec = llvm::SmallVector<Violation, 1>;
+  std::unique_ptr<ImplVec> Impl;
+
+public:
+  // Insert a new Violation if we do not already have one for its effect.
+  void maybeInsert(const Violation &Viol) {
+    if (Impl == nullptr)
+      Impl = std::make_unique<ImplVec>();
+    auto *Iter = _find(Viol.Effect);
----------------
dougsonos wrote:

Done

https://github.com/llvm/llvm-project/pull/99656