State.cpp

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//===--- State.cpp - State chain for the VM and AST Walker ------*- 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
//
//===----------------------------------------------------------------------===//
 
#include "State.h"
#include "Frame.h"
#include "Program.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/OptionalDiagnostic.h"
 
using namespace clang;
using namespace clang::interp;
 
State::~State() {}
 
OptionalDiagnostic State::FFDiag(SourceLocation Loc, diag::kind DiagId,
                                 unsigned ExtraNotes) {
  return diag(Loc, DiagId, ExtraNotes, false);
}
 
OptionalDiagnostic State::FFDiag(const Expr *E, diag::kind DiagId,
                                 unsigned ExtraNotes) {
  if (EvalStatus.Diag)
    return diag(E->getExprLoc(), DiagId, ExtraNotes, false);
  setActiveDiagnostic(false);
  return OptionalDiagnostic();
}
 
OptionalDiagnostic State::FFDiag(SourceInfo SI, diag::kind DiagId,
                                 unsigned ExtraNotes) {
  if (EvalStatus.Diag)
    return diag(SI.getLoc(), DiagId, ExtraNotes, false);
  setActiveDiagnostic(false);
  return OptionalDiagnostic();
}
 
OptionalDiagnostic State::CCEDiag(SourceLocation Loc, diag::kind DiagId,
                                  unsigned ExtraNotes) {
  // Don't override a previous diagnostic. Don't bother collecting
  // diagnostics if we're evaluating for overflow.
  if (!EvalStatus.Diag || !EvalStatus.Diag->empty()) {
    setActiveDiagnostic(false);
    return OptionalDiagnostic();
  }
  return diag(Loc, DiagId, ExtraNotes, true);
}
 
OptionalDiagnostic State::CCEDiag(const Expr *E, diag::kind DiagId,
                                  unsigned ExtraNotes) {
  return CCEDiag(E->getExprLoc(), DiagId, ExtraNotes);
}
 
OptionalDiagnostic State::CCEDiag(SourceInfo SI, diag::kind DiagId,
                                  unsigned ExtraNotes) {
  return CCEDiag(SI.getLoc(), DiagId, ExtraNotes);
}
 
OptionalDiagnostic State::Note(SourceLocation Loc, diag::kind DiagId) {
  if (!hasActiveDiagnostic())
    return OptionalDiagnostic();
  return OptionalDiagnostic(&addDiag(Loc, DiagId));
}
 
void State::addNotes(ArrayRef<PartialDiagnosticAt> Diags) {
  if (hasActiveDiagnostic())
    llvm::append_range(*EvalStatus.Diag, Diags);
}
 
DiagnosticBuilder State::report(SourceLocation Loc, diag::kind DiagId) {
  return Ctx.getDiagnostics().Report(Loc, DiagId);
}
 
/// Add a diagnostic to the diagnostics list.
PartialDiagnostic &State::addDiag(SourceLocation Loc, diag::kind DiagId) {
  PartialDiagnostic PD(DiagId, Ctx.getDiagAllocator());
  EvalStatus.Diag->push_back(std::make_pair(Loc, PD));
  return EvalStatus.Diag->back().second;
}
 
OptionalDiagnostic State::diag(SourceLocation Loc, diag::kind DiagId,
                               unsigned ExtraNotes, bool IsCCEDiag) {
  if (EvalStatus.Diag) {
    if (hasPriorDiagnostic()) {
      return OptionalDiagnostic();
    }
 
    unsigned CallStackNotes = getCallStackDepth() - 1;
    unsigned Limit = Ctx.getDiagnostics().getConstexprBacktraceLimit();
    if (Limit)
      CallStackNotes = std::min(CallStackNotes, Limit + 1);
    if (checkingPotentialConstantExpression())
      CallStackNotes = 0;
 
    setActiveDiagnostic(true);
    setFoldFailureDiagnostic(!IsCCEDiag);
    EvalStatus.Diag->clear();
    EvalStatus.Diag->reserve(1 + ExtraNotes + CallStackNotes);
    addDiag(Loc, DiagId);
    if (!checkingPotentialConstantExpression()) {
      addCallStack(Limit);
    }
    return OptionalDiagnostic(&(*EvalStatus.Diag)[0].second);
  }
  setActiveDiagnostic(false);
  return OptionalDiagnostic();
}
 
void State::addCallStack(unsigned Limit) {
  // Determine which calls to skip, if any.
  unsigned ActiveCalls = getCallStackDepth() - 1;
  unsigned SkipStart = ActiveCalls, SkipEnd = SkipStart;
  if (Limit && Limit < ActiveCalls) {
    SkipStart = Limit / 2 + Limit % 2;
    SkipEnd = ActiveCalls - Limit / 2;
  }
 
  // Walk the call stack and add the diagnostics.
  unsigned CallIdx = 0;
  const Frame *Top = getCurrentFrame();
  const Frame *Bottom = getBottomFrame();
  for (const Frame *F = Top; F != Bottom; F = F->getCaller(), ++CallIdx) {
    SourceRange CallRange = F->getCallRange();
    assert(CallRange.isValid());
 
    // Skip this call?
    if (CallIdx >= SkipStart && CallIdx < SkipEnd) {
      if (CallIdx == SkipStart) {
        // Note that we're skipping calls.
        addDiag(CallRange.getBegin(), diag::note_constexpr_calls_suppressed)
            << unsigned(ActiveCalls - Limit);
      }
      continue;
    }
 
    // Use a different note for an inheriting constructor, because from the
    // user's perspective it's not really a function at all.
    if (const auto *CD =
            dyn_cast_if_present<CXXConstructorDecl>(F->getCallee());
        CD && CD->isInheritingConstructor()) {
      addDiag(CallRange.getBegin(),
              diag::note_constexpr_inherited_ctor_call_here)
          << CD->getParent();
      continue;
    }
 
    SmallString<128> Buffer;
    llvm::raw_svector_ostream Out(Buffer);
    F->describe(Out);
    if (!Buffer.empty())
      addDiag(CallRange.getBegin(), diag::note_constexpr_call_here)
          << Out.str() << CallRange;
  }
}
 
bool State::hasPriorDiagnostic() {
  if (!EvalStatus.Diag->empty()) {
    switch (EvalMode) {
    case EvaluationMode::ConstantFold:
    case EvaluationMode::IgnoreSideEffects:
      if (!HasFoldFailureDiagnostic)
        break;
      // We've already failed to fold something. Keep that diagnostic.
      [[fallthrough]];
    case EvaluationMode::ConstantExpression:
    case EvaluationMode::ConstantExpressionUnevaluated:
      setActiveDiagnostic(false);
      return true;
    }
  }
  return false;
}
 
bool State::keepEvaluatingAfterFailure() const {
  uint64_t Limit = Ctx.getLangOpts().ConstexprStepLimit;
  if (Limit != 0 && !stepsLeft())
    return false;
 
  switch (EvalMode) {
  case EvaluationMode::ConstantExpression:
  case EvaluationMode::ConstantExpressionUnevaluated:
  case EvaluationMode::ConstantFold:
  case EvaluationMode::IgnoreSideEffects:
    return checkingPotentialConstantExpression() ||
           checkingForUndefinedBehavior();
  }
  llvm_unreachable("Missed EvalMode case");
}
 
bool State::keepEvaluatingAfterSideEffect() const {
  switch (EvalMode) {
  case EvaluationMode::IgnoreSideEffects:
    return true;
 
  case EvaluationMode::ConstantExpression:
  case EvaluationMode::ConstantExpressionUnevaluated:
  case EvaluationMode::ConstantFold:
    // By default, assume any side effect might be valid in some other
    // evaluation of this expression from a different context.
    return checkingPotentialConstantExpression() ||
           checkingForUndefinedBehavior();
  }
  llvm_unreachable("Missed EvalMode case");
}
 
bool State::keepEvaluatingAfterUndefinedBehavior() const {
  switch (EvalMode) {
  case EvaluationMode::IgnoreSideEffects:
  case EvaluationMode::ConstantFold:
    return true;
 
  case EvaluationMode::ConstantExpression:
  case EvaluationMode::ConstantExpressionUnevaluated:
    return checkingForUndefinedBehavior();
  }
  llvm_unreachable("Missed EvalMode case");
}