https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88474
Bug ID: 88474
Summary: Inline built-in hypot for -ffast-math
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: jsm28 at gcc dot gnu.org
Target Milestone: ---
Target: i?86-*-*
GCC should support inline code generation for hypot functions, under
appropriate fast-math conditions.
glibc's bits/mathinline.h, for 32-bit non-SSE fast-math x86 only, has:
/* The argument range of the inline version of hypotl is slightly reduced. */
__inline_mathcodeNP2 (hypot, __x, __y,
return __libc_sqrtl (__x * __x + __y * __y))
We're moving away from such inlines in glibc, preferring to leave it to the
compiler to inline standard functions under appropriate conditions. Although
this is filed as a target issue, inlining hypot functions (given
-funsafe-math-optimizations, as it may change results, and -ffinite-math-only,
as it won't be correct for Inf, NaN arguments) is actually reasonably generic.
There are separate cases for when it's possible to do the * + sqrt operations
on a wider (hardware) type, so avoiding reducing the argument range, and when a
wider hardware type is unavailable or inappropriate to use, in which case the
argument range would be reduced by inlining (although that glibc inline still
does it for long double).
