Hello,
according to the C++ standard, numeric_limits::denorm_min should return
min (not 0) when there are no denormals.
Tested with bootstrap+testsuite on x86_64-linux-gnu. I also tested a basic
make all-gcc for vax (only target without denormals apparently) and the
macro did change as expected.
The next step might be to define has_denorm as false in more cases
(-mno-ieee on alpha, -ffast-math on x86, etc) but that's a different
issue.
(this is C++ but I believe Joseph is the floating-point expert, hence the
cc)
gcc/c-family/
2014-09-10 Marc Glisse <marc.gli...@inria.fr>
* c-cppbuiltin.c (builtin_define_float_constants): Correct
__*_DENORM_MIN__ without denormals.
--
Marc GlisseIndex: gcc/c-family/c-cppbuiltin.c
===================================================================
--- gcc/c-family/c-cppbuiltin.c (revision 215103)
+++ gcc/c-family/c-cppbuiltin.c (working copy)
@@ -264,34 +264,27 @@ builtin_define_float_constants (const ch
sprintf (name, "__%s_EPSILON__", name_prefix);
if (fmt->pnan < fmt->p)
/* This is an IBM extended double format, so 1.0 + any double is
representable precisely. */
sprintf (buf, "0x1p%d", fmt->emin - fmt->p);
else
sprintf (buf, "0x1p%d", 1 - fmt->p);
builtin_define_with_hex_fp_value (name, type, decimal_dig, buf, fp_suffix,
fp_cast);
/* For C++ std::numeric_limits<T>::denorm_min. The minimum denormalized
- positive floating-point number, b**(emin-p). Zero for formats that
- don't support denormals. */
+ positive floating-point number, b**(emin-p). The minimum normalized
+ positive floating-point number for formats that don't support
+ denormals. */
sprintf (name, "__%s_DENORM_MIN__", name_prefix);
- if (fmt->has_denorm)
- {
- sprintf (buf, "0x1p%d", fmt->emin - fmt->p);
- builtin_define_with_hex_fp_value (name, type, decimal_dig,
- buf, fp_suffix, fp_cast);
- }
- else
- {
- sprintf (buf, "0.0%s", fp_suffix);
- builtin_define_with_value (name, buf, 0);
- }
+ sprintf (buf, "0x1p%d", fmt->emin - (fmt->has_denorm ? fmt->p : 1));
+ builtin_define_with_hex_fp_value (name, type, decimal_dig,
+ buf, fp_suffix, fp_cast);
sprintf (name, "__%s_HAS_DENORM__", name_prefix);
builtin_define_with_value (name, fmt->has_denorm ? "1" : "0", 0);
/* For C++ std::numeric_limits<T>::has_infinity. */
sprintf (name, "__%s_HAS_INFINITY__", name_prefix);
builtin_define_with_int_value (name,
MODE_HAS_INFINITIES (TYPE_MODE (type)));
/* For C++ std::numeric_limits<T>::has_quiet_NaN. We do not have a
predicate to distinguish a target that has both quiet and
