[LLVMdev] [RFC][Float2Int] Converting (fcmp Pred, x * F, y) to (ICmp ...)

[Stephen Canon]

> On Apr 29, 2015, at 3:00 PM, Stephen Canon <scanon at apple.com> wrote:
> 
>> On Apr 29, 2015, at 2:33 PM, Matt Arsenault <arsenm2 at gmail.com <mailto:arsenm2 at gmail.com>> wrote:
>> 
>>> On Apr 29, 2015, at 10:06 AM, Silviu Baranga <Silviu.Baranga at arm.com <mailto:Silviu.Baranga at arm.com>> wrote:
>>> 
>>> Note that dividing by an integer constant should be a cheap operation
>>> compared to FP multiplication and comparison as this would get lowered to a
>>> multiply+subtract+shift sequence (and should certainly be true on cores with no
>>> FP unit)
>>>  
>> 
>> This is not true on the targets I care about. The integer division (which, even with the division by constant expansion to multiplies with magic constants) would be significantly more expensive.
> 
> What targets *does* this benefit?  Soft-float targets and Cortex-A8?
> 
> Anyway, both integer and floating-point multiplication and division are monotonic, so it suffices to check the two values of x that bracket y/f.

Ah, I see now that y is not a constant.  Slightly more subtle. =)

I’ll respond later.
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