[flang] Complete implementation of OUT_OF_RANGE() (#89334)

The intrinsic function OUT_OF_RANGE() lacks support in lowering and the
runtime. This patch obviates a need for any such support by implementing
OUT_OF_RANGE() via rewriting in semantics. This rewriting of
OUT_OF_RANGE() calls replaces the existing code that folds
OUT_OF_RANGE() calls with constant arguments.

Some changes and fixes were necessary outside of OUT_OF_RANGE()'s
folding code (now rewriting code), whose testing exposed some other
issues worth fixing.

- The common::RealDetails<> template class was recoded in terms of a new
base class with a constexpr constructor, so that the the characteristics
of the various REAL kinds could be queried dynamically as well. This
affected some client usage.
- There were bugs in the code that folds TRANSFER() when the type of X
or MOLD was REAL(10) -- this is a type that occupies 16 bytes per
element in execution memory but only 10 bytes (was 12) in the data of
std::vector<Scalar<>> in a Constant<>.
- Folds of REAL->REAL conversions weren't preserving infinities.

Author: klausler

flang/include/flang/Common/real.h

@@ -108,7 +108,27 @@ static constexpr int PrecisionOfRealKind(int kind) {
   }
 }
 
-template <int BINARY_PRECISION> class RealDetails {
+// RealCharacteristics is constexpr, but also useful when constructed
+// with a non-constant precision argument.
+class RealCharacteristics {
+public:
+  explicit constexpr RealCharacteristics(int p) : binaryPrecision{p} {}
+
+  int binaryPrecision;
+  int bits{BitsForBinaryPrecision(binaryPrecision)};
+  bool isImplicitMSB{binaryPrecision != 64 /*x87*/};
+  int significandBits{binaryPrecision - isImplicitMSB};
+  int exponentBits{bits - significandBits - 1 /*sign*/};
+  int maxExponent{(1 << exponentBits) - 1};
+  int exponentBias{maxExponent / 2};
+  int decimalPrecision{LogBaseTwoToLogBaseTen(binaryPrecision - 1)};
+  int decimalRange{LogBaseTwoToLogBaseTen(exponentBias - 1)};
+  // Number of significant decimal digits in the fraction of the
+  // exact conversion of the least nonzero subnormal.
+  int maxDecimalConversionDigits{MaxDecimalConversionDigits(binaryPrecision)};
+  int maxHexadecimalConversionDigits{
+      MaxHexadecimalConversionDigits(binaryPrecision)};
+
 private:
   // Converts bit widths to whole decimal digits
   static constexpr int LogBaseTwoToLogBaseTen(int logb2) {
@@ -118,33 +138,6 @@ template <int BINARY_PRECISION> class RealDetails {
         (logb2 * LogBaseTenOfTwoTimesTenToThe12th) / TenToThe12th};
     return static_cast<int>(logb10);
   }
-
-public:
-  RT_OFFLOAD_VAR_GROUP_BEGIN
-  static constexpr int binaryPrecision{BINARY_PRECISION};
-  static constexpr int bits{BitsForBinaryPrecision(binaryPrecision)};
-  static constexpr bool isImplicitMSB{binaryPrecision != 64 /*x87*/};
-  static constexpr int significandBits{binaryPrecision - isImplicitMSB};
-  static constexpr int exponentBits{bits - significandBits - 1 /*sign*/};
-  static constexpr int maxExponent{(1 << exponentBits) - 1};
-  static constexpr int exponentBias{maxExponent / 2};
-
-  static constexpr int decimalPrecision{
-      LogBaseTwoToLogBaseTen(binaryPrecision - 1)};
-  static constexpr int decimalRange{LogBaseTwoToLogBaseTen(exponentBias - 1)};
-
-  // Number of significant decimal digits in the fraction of the
-  // exact conversion of the least nonzero subnormal.
-  static constexpr int maxDecimalConversionDigits{
-      MaxDecimalConversionDigits(binaryPrecision)};
-
-  static constexpr int maxHexadecimalConversionDigits{
-      MaxHexadecimalConversionDigits(binaryPrecision)};
-  RT_OFFLOAD_VAR_GROUP_END
-
-  static_assert(binaryPrecision > 0);
-  static_assert(exponentBits > 1);
-  static_assert(exponentBits <= 15);
 };
 
 } // namespace Fortran::common

flang/include/flang/Decimal/binary-floating-point.h

@@ -30,21 +30,20 @@ enum FortranRounding {
   RoundCompatible, /* RC: like RN, but ties go away from 0 */
 };
 
-template <int BINARY_PRECISION>
-class BinaryFloatingPointNumber : public common::RealDetails<BINARY_PRECISION> {
+template <int BINARY_PRECISION> class BinaryFloatingPointNumber {
 public:
-  using Details = common::RealDetails<BINARY_PRECISION>;
-  using Details::binaryPrecision;
-  using Details::bits;
-  using Details::decimalPrecision;
-  using Details::decimalRange;
-  using Details::exponentBias;
-  using Details::exponentBits;
-  using Details::isImplicitMSB;
-  using Details::maxDecimalConversionDigits;
-  using Details::maxExponent;
-  using Details::maxHexadecimalConversionDigits;
-  using Details::significandBits;
+  static constexpr common::RealCharacteristics realChars{BINARY_PRECISION};
+  static constexpr int binaryPrecision{BINARY_PRECISION};
+  static constexpr int bits{realChars.bits};
+  static constexpr int isImplicitMSB{realChars.isImplicitMSB};
+  static constexpr int significandBits{realChars.significandBits};
+  static constexpr int exponentBits{realChars.exponentBits};
+  static constexpr int exponentBias{realChars.exponentBias};
+  static constexpr int maxExponent{realChars.maxExponent};
+  static constexpr int decimalPrecision{realChars.decimalPrecision};
+  static constexpr int decimalRange{realChars.decimalRange};
+  static constexpr int maxDecimalConversionDigits{
+      realChars.maxDecimalConversionDigits};
 
   using RawType = common::HostUnsignedIntType<bits>;
   static_assert(CHAR_BIT * sizeof(RawType) >= bits);

flang/include/flang/Evaluate/complex.h

@@ -104,7 +104,7 @@ extern template class Complex<Real<Integer<16>, 11>>;
 extern template class Complex<Real<Integer<16>, 8>>;
 extern template class Complex<Real<Integer<32>, 24>>;
 extern template class Complex<Real<Integer<64>, 53>>;
-extern template class Complex<Real<Integer<80>, 64>>;
+extern template class Complex<Real<X87IntegerContainer, 64>>;
 extern template class Complex<Real<Integer<128>, 113>>;
 } // namespace Fortran::evaluate::value
 #endif // FORTRAN_EVALUATE_COMPLEX_H_

flang/include/flang/Evaluate/integer.h

@@ -50,9 +50,12 @@ namespace Fortran::evaluate::value {
 // named accordingly in ALL CAPS so that they can be referenced easily in
 // the language standard.
 template <int BITS, bool IS_LITTLE_ENDIAN = isHostLittleEndian,
-    int PARTBITS = BITS <= 32 ? BITS : 32,
+    int PARTBITS = BITS <= 32 ? BITS
+        : BITS % 32 == 0      ? 32
+        : BITS % 16 == 0      ? 16
+                              : 8,
     typename PART = HostUnsignedInt<PARTBITS>,
-    typename BIGPART = HostUnsignedInt<PARTBITS * 2>>
+    typename BIGPART = HostUnsignedInt<PARTBITS * 2>, int ALIGNMENT = BITS>
 class Integer {
 public:
   static constexpr int bits{BITS};
@@ -79,6 +82,8 @@ class Integer {
   static_assert((parts - 1) * partBits + topPartBits == bits);
   static constexpr Part partMask{static_cast<Part>(~0) >> extraPartBits};
   static constexpr Part topPartMask{static_cast<Part>(~0) >> extraTopPartBits};
+  static constexpr int partsWithAlignment{
+      (ALIGNMENT + partBits - 1) / partBits};
 
 public:
   // Some types used for member function results
@@ -1043,14 +1048,16 @@ class Integer {
     }
   }
 
-  Part part_[parts]{};
+  Part part_[partsWithAlignment]{};
 };
 
 extern template class Integer<8>;
 extern template class Integer<16>;
 extern template class Integer<32>;
 extern template class Integer<64>;
-extern template class Integer<80>;
+using X87IntegerContainer =
+    Integer<80, true, 16, std::uint16_t, std::uint32_t, 128>;
+extern template class Integer<80, true, 16, std::uint16_t, std::uint32_t, 128>;
 extern template class Integer<128>;
 } // namespace Fortran::evaluate::value
 #endif // FORTRAN_EVALUATE_INTEGER_H_

flang/include/flang/Evaluate/real.h

@@ -35,20 +35,19 @@ static constexpr std::int64_t ScaledLogBaseTenOfTwo{301029995664};
 // class template must be (or look like) an instance of Integer<>;
 // the second specifies the number of effective bits (binary precision)
 // in the fraction.
-template <typename WORD, int PREC>
-class Real : public common::RealDetails<PREC> {
+template <typename WORD, int PREC> class Real {
 public:
   using Word = WORD;
   static constexpr int binaryPrecision{PREC};
-  using Details = common::RealDetails<PREC>;
-  using Details::exponentBias;
-  using Details::exponentBits;
-  using Details::isImplicitMSB;
-  using Details::maxExponent;
-  using Details::significandBits;
+  static constexpr common::RealCharacteristics realChars{PREC};
+  static constexpr int exponentBias{realChars.exponentBias};
+  static constexpr int exponentBits{realChars.exponentBits};
+  static constexpr int isImplicitMSB{realChars.isImplicitMSB};
+  static constexpr int maxExponent{realChars.maxExponent};
+  static constexpr int significandBits{realChars.significandBits};
 
   static constexpr int bits{Word::bits};
-  static_assert(bits >= Details::bits);
+  static_assert(bits >= realChars.bits);
   using Fraction = Integer<binaryPrecision>; // all bits made explicit
 
   template <typename W, int P> friend class Real;
@@ -205,8 +204,8 @@ class Real : public common::RealDetails<PREC> {
   }
 
   static constexpr int DIGITS{binaryPrecision};
-  static constexpr int PRECISION{Details::decimalPrecision};
-  static constexpr int RANGE{Details::decimalRange};
+  static constexpr int PRECISION{realChars.decimalPrecision};
+  static constexpr int RANGE{realChars.decimalRange};
   static constexpr int MAXEXPONENT{maxExponent - exponentBias};
   static constexpr int MINEXPONENT{2 - exponentBias};
   Real RRSPACING() const;
@@ -371,6 +370,10 @@ class Real : public common::RealDetails<PREC> {
       return result;
     }
     bool isNegative{x.IsNegative()};
+    if (x.IsInfinite()) {
+      result.value = Infinity(isNegative);
+      return result;
+    }
     A absX{x};
     if (isNegative) {
       absX = x.Negate();
@@ -493,7 +496,7 @@ extern template class Real<Integer<16>, 11>; // IEEE half format
 extern template class Real<Integer<16>, 8>; // the "other" half format
 extern template class Real<Integer<32>, 24>; // IEEE single
 extern template class Real<Integer<64>, 53>; // IEEE double
-extern template class Real<Integer<80>, 64>; // 80387 extended precision
+extern template class Real<X87IntegerContainer, 64>; // 80387 extended precision
 extern template class Real<Integer<128>, 113>; // IEEE quad
 // N.B. No "double-double" support.
 } // namespace Fortran::evaluate::value

flang/include/flang/Evaluate/type.h

@@ -296,7 +296,10 @@ class Type<TypeCategory::Real, KIND>
 public:
   static constexpr int precision{common::PrecisionOfRealKind(KIND)};
   static constexpr int bits{common::BitsForBinaryPrecision(precision)};
-  using Scalar = value::Real<value::Integer<bits>, precision>;
+  using Scalar =
+      value::Real<std::conditional_t<precision == 64,
+                      value::X87IntegerContainer, value::Integer<bits>>,
+          precision>;
 };
 
 // The KIND type parameter on COMPLEX is the kind of each of its components.

flang/lib/Decimal/big-radix-floating-point.h

@@ -83,6 +83,8 @@ template <int PREC, int LOG10RADIX = 16> class BigRadixFloatingPointNumber {
     return *this;
   }
 
+  RT_API_ATTRS bool IsInteger() const { return exponent_ >= 0; }
+
   // Converts decimal floating-point to binary.
   RT_API_ATTRS ConversionToBinaryResult<PREC> ConvertToBinary();
 

flang/lib/Evaluate/complex.cpp

@@ -120,6 +120,6 @@ template class Complex<Real<Integer<16>, 11>>;
 template class Complex<Real<Integer<16>, 8>>;
 template class Complex<Real<Integer<32>, 24>>;
 template class Complex<Real<Integer<64>, 53>>;
-template class Complex<Real<Integer<80>, 64>>;
+template class Complex<Real<X87IntegerContainer, 64>>;
 template class Complex<Real<Integer<128>, 113>>;
 } // namespace Fortran::evaluate::value