Fortran: error recovery while simplifying expressions [PR103707,PR106987]

Fortran: error recovery while simplifying expressions [PR103707,PR106987]

When an exception is encountered during simplification of arithmetic
expressions, the result may depend on whether range-checking is active
(-frange-check) or not.  However, the code path in the front-end should
stay the same for "soft" errors for which the exception is triggered by the
check, while "hard" errors should always terminate the simplification, so
that error recovery is independent of the flag.  Separation of arithmetic
error codes into "hard" and "soft" errors shall be done consistently via
is_hard_arith_error().

	PR fortran/103707
	PR fortran/106987

gcc/fortran/ChangeLog:

	* arith.cc (is_hard_arith_error): New helper function to determine
	whether an arithmetic error is "hard" or not.
	(check_result): Use it.
	(gfc_arith_divide): Set "Division by zero" only for regular
	numerators of real and complex divisions.
	(reduce_unary): Use is_hard_arith_error to determine whether a hard
	or (recoverable) soft error was encountered.  Terminate immediately
	on hard error, otherwise remember code of first soft error.
	(reduce_binary_ac): Likewise.
	(reduce_binary_ca): Likewise.
	(reduce_binary_aa): Likewise.

gcc/testsuite/ChangeLog:

	* gfortran.dg/pr99350.f90:
	* gfortran.dg/arithmetic_overflow_3.f90: New test.