poor codegen for abs(), and div by literal?

[kinke]

On Thursday, 7 February 2019 at 23:35:36 UTC, H. S. Teoh wrote:
> On Thu, Feb 07, 2019 at 11:15:08PM +0000, NaN via Digitalmars-d
>> So to do the abs(), it stores to memory from XMM reg, loads 
>> into x87 FPU regs, does the abs with the old FPU instruction, 
>> then for some reason stores the result as a double, loads that 
>> back into an XMM, converts it back to single.
>
> Which compiler are you using?
>
> For performance / codegen quality issues, I highly recommend 
> looking at the output of ldc or gdc, rather than dmd.

Or just open std.math to see the simple reason for the old FPU 
being used:

```
real fabs(real x) @safe pure nothrow @nogc { pragma(inline, 
true); return core.math.fabs(x); }
//FIXME
///ditto
double fabs(double x) @safe pure nothrow @nogc { return 
fabs(cast(real) x); }
//FIXME
///ditto
float fabs(float x) @safe pure nothrow @nogc { return 
fabs(cast(real) x); }
```

Just one of many functions still operating with `real` precision 
only.