Re: [PATCH] fenv fixes for x86_64/i386/ia64

[Steven Munroe <munroesj@us.ibm.com>]

Jakub Jelinek wrote:
> Hi!
>
> feholdexcept is supposed to clear the sticky exception bits:
> "The feholdexcept function saves the current floating-point environment in the object
> pointed to by envp, clears the floating-point status flags, and then installs a non-stop
> (continue on floating-point exceptions) mode, if available, for all floating-point
> exceptions."
> and
> "A floating-point status flag is a system variable whose value is set
> (but never cleared) when a floating-point exception is raised, which occurs as a side effect
> of exceptional floating-point arithmetic to provide auxiliary information."
>
> Several feholdexcept implementations didn't handle this right.
> Also, e.g. feupdateenv was a stub on x86_64 eventhough it is IMHO easily
> implementable and other arches had bugs in it too (e.g. ia64 would rise
> wrong exceptions and always return a failure).
> I added a new testcase for feholdexcept/feupdateenv (hopefully I haven't
> misinterpreted the standard) and I believe other arches (ppc*, s390*, ...)
> will need some care too.
>   

powerpc32 and powerpc64 both show two failures with the new test-fenv:

Test: feholdexcept_tests FE_DIVBYZERO|FE_INVALID test
  Fail: Exception "DIVBYZERO" is not set
  Pass: Exception "INVALID" is set
  Pass: Exception "INEXACT" is not set
  Pass: Exception "UNDERFLOW" is not set
  Pass: Exception "OVERFLOW" is not set

and

Test: feholdexcept_tests FE_INEXACT|FE_INVALID test
  Pass: Exception "DIVBYZERO" is not set
  Fail: Exception "INVALID" is not set
  Pass: Exception "INEXACT" is set
  Pass: Exception "UNDERFLOW" is not set
  Pass: Exception "OVERFLOW" is not set

We will look into this.