[LLVMdev] Reference Manual Clarifications 2
sabre at nondot.org
Tue Apr 1 11:48:49 PDT 2008
On Mon, 31 Mar 2008, Jon Sargeant wrote:
> The fptrunc instruction states "If the value cannot fit within the
> destination type, ty2, then the results are undefined." This is fine, but
> what about other floating-point operations that can overflow? For example,
> does 'mul double 1.0e300, 1.0e300' produce +infinity or is it undefined?
It is defined by IEEE to be inf.
> think LLVM should treat floating-point overflows consistently. On a similar
> note, what is the result of division by zero for fdiv? infinity or
IEEE also specifies these, but I don't know the answer off-hand.
> The manual needs to state the rounding mode of the fptrunc, uitofp, and
> sitofp instruction (if only to say it's undefined). I recommend
Everything is implicitly assumed to be in the default rounding mode.
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