[flang] Improve warnings for invalid arguments when folding host runtime (#96807)

This is another attempt at a change that Jean made to Phabricator in
https://reviews.llvm.org/D116934. That attempt ran into problems with
building on Windows.

This change improves the messages that are produced when running into
invalid arguments during constant folding.

Note that the original attempt at implementing this contained additional
code in .../llvm-project/flang/test/Evaluate/folding04.f90:
```
  !WARN: warning: argument 'x' must be strictly positive
  real(8), parameter :: nan_r8_dlog1 = dlog(-0.1_8)
  TEST_ISNAN(nan_r8_dlog1)
```
For reasons I don't understand, this additional code caused the Windows
build to fail. So this new version of the update does not contain that
code.

Author: psteinfeld

flang/lib/Evaluate/intrinsics-library.cpp

@@ -633,10 +633,243 @@ static DynamicType BiggerType(DynamicType type) {
   return type;
 }
 
+/// Structure to register intrinsic argument checks that must be performed.
+using ArgumentVerifierFunc = bool (*)(
+    const std::vector<Expr<SomeType>> &, FoldingContext &);
+struct ArgumentVerifier {
+  using Key = std::string_view;
+  // Needed for implicit compare with keys.
+  constexpr operator Key() const { return key; }
+  Key key;
+  ArgumentVerifierFunc verifier;
+};
+
+static constexpr int lastArg{-1};
+static constexpr int firstArg{0};
+
+static const Expr<SomeType> &GetArg(
+    int position, const std::vector<Expr<SomeType>> &args) {
+  if (position == lastArg) {
+    CHECK(!args.empty());
+    return args.back();
+  }
+  CHECK(position >= 0 && static_cast<std::size_t>(position) < args.size());
+  return args[position];
+}
+
+template <typename T>
+static bool IsInRange(const Expr<T> &expr, int lb, int ub) {
+  if (auto scalar{GetScalarConstantValue<T>(expr)}) {
+    auto lbValue{Scalar<T>::FromInteger(value::Integer<8>{lb}).value};
+    auto ubValue{Scalar<T>::FromInteger(value::Integer<8>{ub}).value};
+    return Satisfies(RelationalOperator::LE, lbValue.Compare(*scalar)) &&
+        Satisfies(RelationalOperator::LE, scalar->Compare(ubValue));
+  }
+  return true;
+}
+
+/// Verify that the argument in an intrinsic call belongs to [lb, ub] if is
+/// real.
+template <int lb, int ub>
+static bool VerifyInRangeIfReal(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  if (const auto *someReal{
+          std::get_if<Expr<SomeReal>>(&GetArg(firstArg, args).u)}) {
+    bool isInRange{
+        std::visit([&](const auto &x) -> bool { return IsInRange(x, lb, ub); },
+            someReal->u)};
+    if (!isInRange) {
+      context.messages().Say(
+          "argument is out of range [%d., %d.]"_warn_en_US, lb, ub);
+    }
+    return isInRange;
+  }
+  return true;
+}
+
+template <int argPosition, const char *argName>
+static bool VerifyStrictlyPositiveIfReal(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  if (const auto *someReal =
+          std::get_if<Expr<SomeReal>>(&GetArg(argPosition, args).u)) {
+    const bool isStrictlyPositive{std::visit(
+        [&](const auto &x) -> bool {
+          using T = typename std::decay_t<decltype(x)>::Result;
+          auto scalar{GetScalarConstantValue<T>(x)};
+          return Satisfies(
+              RelationalOperator::LT, Scalar<T>{}.Compare(*scalar));
+        },
+        someReal->u)};
+    if (!isStrictlyPositive) {
+      context.messages().Say(
+          "argument '%s' must be strictly positive"_warn_en_US, argName);
+    }
+    return isStrictlyPositive;
+  }
+  return true;
+}
+
+/// Verify that an intrinsic call argument is not zero if it is real.
+template <int argPosition, const char *argName>
+static bool VerifyNotZeroIfReal(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  if (const auto *someReal =
+          std::get_if<Expr<SomeReal>>(&GetArg(argPosition, args).u)) {
+    const bool isNotZero{std::visit(
+        [&](const auto &x) -> bool {
+          using T = typename std::decay_t<decltype(x)>::Result;
+          auto scalar{GetScalarConstantValue<T>(x)};
+          return !scalar || !scalar->IsZero();
+        },
+        someReal->u)};
+    if (!isNotZero) {
+      context.messages().Say(
+          "argument '%s' must be different from zero"_warn_en_US, argName);
+    }
+    return isNotZero;
+  }
+  return true;
+}
+
+/// Verify that the argument in an intrinsic call is not zero if is complex.
+static bool VerifyNotZeroIfComplex(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  if (const auto *someComplex =
+          std::get_if<Expr<SomeComplex>>(&GetArg(firstArg, args).u)) {
+    const bool isNotZero{std::visit(
+        [&](const auto &z) -> bool {
+          using T = typename std::decay_t<decltype(z)>::Result;
+          auto scalar{GetScalarConstantValue<T>(z)};
+          return !scalar || !scalar->IsZero();
+        },
+        someComplex->u)};
+    if (!isNotZero) {
+      context.messages().Say(
+          "complex argument must be different from zero"_warn_en_US);
+    }
+    return isNotZero;
+  }
+  return true;
+}
+
+// Verify that the argument in an intrinsic call is not zero and not a negative
+// integer.
+static bool VerifyGammaLikeArgument(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  if (const auto *someReal =
+          std::get_if<Expr<SomeReal>>(&GetArg(firstArg, args).u)) {
+    const bool isValid{std::visit(
+        [&](const auto &x) -> bool {
+          using T = typename std::decay_t<decltype(x)>::Result;
+          auto scalar{GetScalarConstantValue<T>(x)};
+          if (scalar) {
+            return !scalar->IsZero() &&
+                !(scalar->IsNegative() &&
+                    scalar->ToWholeNumber().value == scalar);
+          }
+          return true;
+        },
+        someReal->u)};
+    if (!isValid) {
+      context.messages().Say(
+          "argument must not be a negative integer or zero"_warn_en_US);
+    }
+    return isValid;
+  }
+  return true;
+}
+
+// Verify that two real arguments are not both zero.
+static bool VerifyAtan2LikeArguments(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  if (const auto *someReal =
+          std::get_if<Expr<SomeReal>>(&GetArg(firstArg, args).u)) {
+    const bool isValid{std::visit(
+        [&](const auto &typedExpr) -> bool {
+          using T = typename std::decay_t<decltype(typedExpr)>::Result;
+          auto x{GetScalarConstantValue<T>(typedExpr)};
+          auto y{GetScalarConstantValue<T>(GetArg(lastArg, args))};
+          if (x && y) {
+            return !(x->IsZero() && y->IsZero());
+          }
+          return true;
+        },
+        someReal->u)};
+    if (!isValid) {
+      context.messages().Say(
+          "'x' and 'y' arguments must not be both zero"_warn_en_US);
+    }
+    return isValid;
+  }
+  return true;
+}
+
+template <ArgumentVerifierFunc... F>
+static bool CombineVerifiers(
+    const std::vector<Expr<SomeType>> &args, FoldingContext &context) {
+  return (... & F(args, context));
+}
+
+/// Define argument names to be used error messages when the intrinsic have
+/// several arguments.
+static constexpr char xName[]{"x"};
+static constexpr char pName[]{"p"};
+
+/// Register argument verifiers for all intrinsics folded with runtime.
+static constexpr ArgumentVerifier intrinsicArgumentVerifiers[]{
+    {"acos", VerifyInRangeIfReal<-1, 1>},
+    {"asin", VerifyInRangeIfReal<-1, 1>},
+    {"atan2", VerifyAtan2LikeArguments},
+    {"bessel_y0", VerifyStrictlyPositiveIfReal<firstArg, xName>},
+    {"bessel_y1", VerifyStrictlyPositiveIfReal<firstArg, xName>},
+    {"bessel_yn", VerifyStrictlyPositiveIfReal<lastArg, xName>},
+    {"gamma", VerifyGammaLikeArgument},
+    {"log",
+        CombineVerifiers<VerifyStrictlyPositiveIfReal<firstArg, xName>,
+            VerifyNotZeroIfComplex>},
+    {"log10", VerifyStrictlyPositiveIfReal<firstArg, xName>},
+    {"log_gamma", VerifyGammaLikeArgument},
+    {"mod", VerifyNotZeroIfReal<lastArg, pName>},
+};
+
+const ArgumentVerifierFunc *findVerifier(const std::string &intrinsicName) {
+  static constexpr Fortran::common::StaticMultimapView<ArgumentVerifier>
+      verifiers(intrinsicArgumentVerifiers);
+  static_assert(verifiers.Verify(), "map must be sorted");
+  auto range{verifiers.equal_range(intrinsicName)};
+  if (range.first != range.second) {
+    return &range.first->verifier;
+  }
+  return nullptr;
+}
+
+/// Ensure argument verifiers, if any, are run before calling the runtime
+/// wrapper to fold an intrinsic.
+static HostRuntimeWrapper AddArgumentVerifierIfAny(
+    const std::string &intrinsicName, const HostRuntimeFunction &hostFunction) {
+  if (const auto *verifier{findVerifier(intrinsicName)}) {
+    const HostRuntimeFunction *hostFunctionPtr = &hostFunction;
+    return [hostFunctionPtr, verifier](
+               FoldingContext &context, std::vector<Expr<SomeType>> &&args) {
+      const bool validArguments{(*verifier)(args, context)};
+      if (!validArguments) {
+        // Silence fp signal warnings since a more detailed warning about
+        // invalid arguments was already emitted.
+        parser::Messages localBuffer;
+        parser::ContextualMessages localMessages{&localBuffer};
+        FoldingContext localContext{context, localMessages};
+        return hostFunctionPtr->folder(localContext, std::move(args));
+      }
+      return hostFunctionPtr->folder(context, std::move(args));
+    };
+  }
+  return hostFunction.folder;
+}
+
 std::optional<HostRuntimeWrapper> GetHostRuntimeWrapper(const std::string &name,
     DynamicType resultType, const std::vector<DynamicType> &argTypes) {
   if (const auto *hostFunction{SearchHostRuntime(name, resultType, argTypes)}) {
-    return hostFunction->folder;
+    return AddArgumentVerifierIfAny(name, *hostFunction);
   }
   // If no exact match, search with "bigger" types and insert type
   // conversions around the folder.
@@ -647,7 +880,8 @@ std::optional<HostRuntimeWrapper> GetHostRuntimeWrapper(const std::string &name,
   }
   if (const auto *hostFunction{
           SearchHostRuntime(name, biggerResultType, biggerArgTypes)}) {
-    return [hostFunction, resultType](
+    auto hostFolderWithChecks{AddArgumentVerifierIfAny(name, *hostFunction)};
+    return [hostFunction, resultType, hostFolderWithChecks](
                FoldingContext &context, std::vector<Expr<SomeType>> &&args) {
       auto nArgs{args.size()};
       for (size_t i{0}; i < nArgs; ++i) {
@@ -657,7 +891,7 @@ std::optional<HostRuntimeWrapper> GetHostRuntimeWrapper(const std::string &name,
       }
       return Fold(context,
           ConvertToType(
-              resultType, hostFunction->folder(context, std::move(args)))
+              resultType, hostFolderWithChecks(context, std::move(args)))
               .value());
     };
   }

flang/test/Evaluate/folding04.f90

@@ -17,24 +17,42 @@ module real_tests
   !WARN: warning: division by zero
   real(4), parameter :: r4_ninf = -1._4/0._4
 
-  !WARN: warning: invalid argument on evaluation of intrinsic function or operation
+  !WARN: warning: argument is out of range [-1., 1.]
   real(4), parameter :: nan_r4_acos1 = acos(1.1)
   TEST_ISNAN(nan_r4_acos1)
-  !WARN: warning: invalid argument on evaluation of intrinsic function or operation
+  !WARN: warning: argument is out of range [-1., 1.]
   real(4), parameter :: nan_r4_acos2 = acos(r4_pmax)
   TEST_ISNAN(nan_r4_acos2)
-  !WARN: warning: invalid argument on evaluation of intrinsic function or operation
+  !WARN: warning: argument is out of range [-1., 1.]
   real(4), parameter :: nan_r4_acos3 = acos(r4_nmax)
   TEST_ISNAN(nan_r4_acos3)
-  !WARN: warning: invalid argument on evaluation of intrinsic function or operation
+  !WARN: warning: argument is out of range [-1., 1.]
   real(4), parameter :: nan_r4_acos4 = acos(r4_ninf)
   TEST_ISNAN(nan_r4_acos4)
-  !WARN: warning: invalid argument on evaluation of intrinsic function or operation
+  !WARN: warning: argument is out of range [-1., 1.]
   real(4), parameter :: nan_r4_acos5 = acos(r4_pinf)
   TEST_ISNAN(nan_r4_acos5)
+  !WARN: warning: argument is out of range [-1., 1.]
+  real(8), parameter :: nan_r8_dasin1 = dasin(-1.1_8)
+  TEST_ISNAN(nan_r8_dasin1)
+  !WARN: warning: complex argument must be different from zero
+  complex(4), parameter :: c4_clog1 = clog((0., 0.))
   !WARN: warning: MOD: P argument is zero
   real(4), parameter :: nan_r4_mod = mod(3.5, 0.)
   TEST_ISNAN(nan_r4_mod)
+  real(4), parameter :: ok_r4_gamma = gamma(-1.1)
+  !WARN: warning: argument must not be a negative integer or zero
+  real(4), parameter :: r4_gamma1 = gamma(0.)
+  !WARN: warning: argument must not be a negative integer or zero
+  real(4), parameter :: r4_gamma2 = gamma(-1.)
+  real(4), parameter :: ok_r4_log_gamma = log_gamma(-2.001)
+  !WARN: warning: argument must not be a negative integer or zero
+  real(4), parameter :: r4_log_gamma1 = log_gamma(0.)
+  !WARN: warning: argument must not be a negative integer or zero
+  real(4), parameter :: r4_log_gamma2 = log_gamma(-100001.)
+  !WARN: warning: 'x' and 'y' arguments must not be both zero
+  real(4), parameter :: r4_atan2 = atan2(0., 0.)
+
   !WARN: warning: overflow on evaluation of intrinsic function or operation
   logical, parameter :: test_exp_overflow = exp(256._4).EQ.r4_pinf
  contains