FASTFLOAT_ASSUME and Clang related crutches cleanup.

Author: IRainman

include/fast_float/bigint.h

@@ -618,11 +618,20 @@ struct bigint : pow5_tables<> {
       exp -= small_step;
     }
     if (exp != 0) {
-      // Work around clang bug https://godbolt.org/z/zedh7rrhc
-      // This is similar to https://github.com/llvm/llvm-project/issues/47746,
-      // except the workaround described there don't work here
-      FASTFLOAT_TRY(small_mul(vec, limb((static_cast<void>(small_power_of_5[0]),
-                                         small_power_of_5[exp]))));
+      FASTFLOAT_TRY(small_mul(
+          vec,
+          limb(
+#if defined(__clang__)
+              // Work around clang bug https://godbolt.org/z/zedh7rrhc
+              // This is similar to
+              // https://github.com/llvm/llvm-project/issues/47746, except
+              // the workaround described there don't work here
+              (static_cast<void>(small_power_of_5[0]), small_power_of_5[exp])
+#else
+              small_power_of_5[exp]
+#endif
+
+                  )));
     }
 
     return true;

include/fast_float/constexpr_feature_detect.h

@@ -54,7 +54,7 @@
 #define FASTFLOAT_INLINE_VARIABLE static constexpr
 #endif
 
-// Before C++17, constexpr variables may need an out-of-class definition.
+// Before C++17 constexpr variables may need an out-of-class definition.
 #if __cplusplus >= 201703L || (defined(_MSC_VER) && _MSVC_LANG >= 201703L)
 #define FASTFLOAT_DETAIL_MUST_DEFINE_CONSTEXPR_VARIABLE 0
 #else
@@ -98,13 +98,15 @@
 #define FASTFLOAT_HAS_BUILTIN(x) false
 #endif
 
-#if defined(FASTFLOAT_ASSUME)
-// user provided solution
-#elif defined(__cpp_attrubute_assume)
-// For support attribute [[assume]] is declared in P1774
-#define FASTFLOAT_ASSUME(expr) [[assume(expr)]]
-#else
-#define FASTFLOAT_ASSUME(expr)
-#endif
+// #if defined(FASTFLOAT_ASSUME)
+//  user provided solution
+// #elif defined(__cpp_attrubute_assume)
+//  For support attribute [[assume]] is declared in P1774
+#define FASTFLOAT_ASSUME(expr)                                                 \
+  assert(expr);                                                                \
+  [[assume(expr)]]
+// #else
+// #define FASTFLOAT_ASSUME(expr)
+// #endif
 
 #endif // FASTFLOAT_CONSTEXPR_FEATURE_DETECT_H

include/fast_float/float_common.h

@@ -944,8 +944,12 @@ constexpr uint16_t
 template <>
 inline constexpr std::float16_t
 binary_format<std::float16_t>::exact_power_of_ten(am_pow_t power) {
+#if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
-  return (void)powers_of_ten[0], powers_of_ten[power];
+  return (void)max_mantissa[0], max_mantissa[power];
+#else
+  return max_mantissa[power];
+#endif
 }
 
 template <>
@@ -989,9 +993,12 @@ inline constexpr am_mant_t
 binary_format<std::float16_t>::max_mantissa_fast_path(am_pow_t power) {
   // caller is responsible to ensure that
   FASTFLOAT_ASSUME(power >= 0 && power <= 4);
-  //
+#if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
   return (void)max_mantissa[0], max_mantissa[power];
+#else
+  return max_mantissa[power];
+#endif
 }
 
 template <>
@@ -1077,8 +1084,12 @@ constexpr uint16_t
 template <>
 inline constexpr std::bfloat16_t
 binary_format<std::bfloat16_t>::exact_power_of_ten(am_pow_t power) {
+#if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
-  return (void)powers_of_ten[0], powers_of_ten[power];
+  return (void)max_mantissa[0], max_mantissa[power];
+#else
+  return max_mantissa[power];
+#endif
 }
 
 template <>
@@ -1122,9 +1133,12 @@ inline constexpr am_mant_t
 binary_format<std::bfloat16_t>::max_mantissa_fast_path(am_pow_t power) {
   // caller is responsible to ensure that
   FASTFLOAT_ASSUME(power >= 0 && power <= 3);
-  //
+#if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
   return (void)max_mantissa[0], max_mantissa[power];
+#else
+  return max_mantissa[power];
+#endif
 }
 
 template <>
@@ -1186,7 +1200,7 @@ template <>
 inline constexpr am_mant_t
 binary_format<double>::max_mantissa_fast_path(am_pow_t power) {
   // caller is responsible to ensure that
-  // FASTFLOAT_ASSUME(power >= 0 && power <= 22);
+  FASTFLOAT_ASSUME(power >= 0 && power <= 22);
 #if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
   return (void)max_mantissa[0], max_mantissa[power];
@@ -1199,7 +1213,7 @@ template <>
 inline constexpr am_mant_t
 binary_format<float>::max_mantissa_fast_path(am_pow_t power) {
   // caller is responsible to ensure that
-  // FASTFLOAT_ASSUME(power >= 0 && power <= 10);
+  FASTFLOAT_ASSUME(power >= 0 && power <= 10);
 #if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
   return (void)max_mantissa[0], max_mantissa[power];
@@ -1212,7 +1226,7 @@ template <>
 inline constexpr double
 binary_format<double>::exact_power_of_ten(am_pow_t power) {
   // caller is responsible to ensure that
-  // FASTFLOAT_ASSUME(power >= 0 && power <= 22);
+  FASTFLOAT_ASSUME(power >= 0 && power <= 22);
 #if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
   return (void)powers_of_ten[0], powers_of_ten[power];
@@ -1225,7 +1239,7 @@ template <>
 inline constexpr float
 binary_format<float>::exact_power_of_ten(am_pow_t power) {
   // caller is responsible to ensure that
-  // FASTFLOAT_ASSUME(power >= 0 && power <= 10);
+  FASTFLOAT_ASSUME(power >= 0 && power <= 10);
 #if defined(__clang__)
   // Work around clang bug https://godbolt.org/z/zedh7rrhc
   return (void)powers_of_ten[0], powers_of_ten[power];

include/fast_float/parse_number.h

@@ -218,9 +218,11 @@ clinger_fast_path_impl(am_mant_t const mantissa, am_pow_t const exponent,
     // We could check it first (before the previous branch), but
     // there might be performance advantages at having the check
     // be last.
+    if (!is_constant_evaluated()
 #ifndef FASTFLOAT_ONLY_ROUNDS_TO_NEAREST_SUPPORTED
-    if (detail::rounds_to_nearest()) {
+        && detail::rounds_to_nearest()
 #endif
+    ) {
       // We have that fegetround() == FE_TONEAREST.
       // Next is Clinger's fast path.
       if (mantissa <= binary_format<T>::max_mantissa_fast_path()) {
@@ -263,8 +265,8 @@ clinger_fast_path_impl(am_mant_t const mantissa, am_pow_t const exponent,
         }
 #endif
         return true;
-      }
 #endif
+      }
     }
   }
   return false;