On 03/31/2010 11:25 AM, Vincent Lefevre wrote:
On 2010-03-31 11:04:03 +0200, Marc Glisse wrote:
IMHO this transformation mostly makes sense for the
-ffinite-math-only case where you can replace: "put a constant and
multiply/divide" by "put a constant and add/sub" and never care
about extracting the exponent, overflowing, or anything else. And in
that case, it does look like a nice optimization.
I suppose that this could be interesting only if a same register
can be seen as a FP one and an integer one (for the addition on
the exponent field), hoping that mixing both kinds of operations
won't stall the pipeline.
Indeed, this is a problem on Intel chips looking at the definition of
TARGET_SSE_TYPELESS_STORES (search for X86_TUNE_SSE_TYPELESS_STORES in
config/i386/i386.c).
Paolo
