Compiler can do more optimizations if it is allowed to generate code that could cause exceptions (-TENV:X=0..4)
X = 0 no speculative code motion
X = 1 IEEE-754 underflow and inexact FPE disabled (default -O0 and -O2)
X = 2 all IEEE-754 exceptions disabled except 1/0 (default -O3)
X = 3 all IEEE-754 exceptions are disabled
X = 4 memory access exceptions are disabled
IF-conversion with conditional moves for Software Pipelining (with -O3):
Removing IF(…) will cause divide by zero!
In this case this exception must be ignored
Note: transf applied already at -O3 & X=1!