floating-WTF

[dennis luehring]

can you give us a complete out-of-the-box compileable example (with 
imports,main,etc.) with both examples the working/and nonworking

does it work correct with dmd(32bit)?

is this "calculate2" needed to reproduce the behavior?

and what compiler did you test: dmd64, (dmd32?), ...?

Am 24.01.2012 16:20, schrieb sclytrack:
>
>
> void calculate2(float a, float b)
> {
> 	float s1 = 1.0 - a;
> 	float s2 = a * b;
> 	writeln(s2);
> 	writeln(a * b);
> }
>
> ----------------
> Output:
> t*b= 0
> t*b= 1.5
> ----------------
>
>
> 	assume	CS:.text._D4main10calculate2FffZv
> _D4main10calculate2FffZv:
> 		push	RBP
> 		mov	RBP,RSP
> 		sub	RSP,020h
> 		movss	-010h[RBP],XMM0
> 		movss	-8[RBP],XMM1
> 		mov	RAX,03FF0000000000000h
> 		mov	-020h[RBP],RAX
> 		movsd	XMM2,-020h[RBP]
> 		cvtss2sd	XMM1,XMM1
> 		subsd	XMM2,XMM1
> ------conversion but xmm2 is no longer used
> 		cvtsd2ss	XMM2,XMM2
> ------precision error multiplication
> 		mulss	XMM1,XMM0
> 		movss	-018h[RBP],XMM1
> 		movss	XMM0,-018h[RBP]
> 		call	  _D3std5stdio14__T7writelnTfZ7writelnFfZv at PC32
> 		movss	XMM0,-8[RBP]
> 		movss	XMM1,-010h[RBP]
> 		mulss	XMM0,XMM1
> 		call	  _D3std5stdio14__T7writelnTfZ7writelnFfZv at PC32
> 		leave
> 		ret
> 		nop
> 		nop
> 		nop
>
> ------------
> DMD64 D Compiler v2.057
> Ubuntu 11.10