On Wednesday, 18 May 2016 at 19:53:10 UTC, Era Scarecrow wrote:
On Wednesday, 18 May 2016 at 19:36:59 UTC, tsbockman wrote:
I agree that intrinsics for this would be nice. I doubt that
any current D platform is actually computing the full 128 bit
result for every 64 bit multiply though - that would waste
both power and performance, for most programs.
Except the 128 result is _already_ there for 0 cost (at least
for x86 instructions that I'm aware).
Can you give me a source for this, or at least the name of the
relevant op code? (I'm new to x86 assembly.)
There's bound to be enough cases (say pseudo random number
generation, encryption, or numerical processing above 64bits)
I'd like access to it supported by the language and not having
to inject instructions using the asm command.
Of course it would be useful to have in the language; I wasn't
disputing that. I'd like to have as much support for 128-bit
integers in the language as possible. Among other things, this
would greatly simplify getting 128-bit floating-point working.
I'm just surprised that the CPU would really calculate the upper
64 bits of a multiply without being explicitly asked to.
