https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77928
Bug ID: 77928
Summary: Add __builtin_iseqsig
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: jsm28 at gcc dot gnu.org
Target Milestone: ---
TS 18661-1 defines a type-generic floating-point comparison macro iseqsig, that
compares its arguments for equality but generates the "invalid" exception (and
sets errno) if either argument is NaN, unlike ==.
GCC should have a corresponding __builtin_iseqsig that does the comparison and
raises "invalid" as needed (but without setting errno, so it could only be used
to implement the standard macro if -fno-math-errno). As with existing
type-generic comparison functions the logic in fold_builtin_unordered_cmp is
needed to convert the arguments to a common type. This operation is equivalent
to (x <= y) && (x >= y) (with arguments only evaluated once, of course), though
some architectures may have more efficient ways of doing such a comparison (and
if the architecture lacks support for exceptions, simple == can be used).
However, various architectures have bugs where the <= comparison fails to raise
the exception it should for NaN arguments (bug 52451, bug 58684, bug 77918).
