xmlvm-users

[xmlvm-users] Rotate Right

[Troy G. <tro...@gm...>]

>From what I can tell, it looks like the objective C instruction might not
always be the same when doing a shift right.  I posted the following Java
code and corresponding Objective C code to illustrate this.  In Java the
value ends up positive and Objective C negative.  I'm not sure if the left
shift has this same issue.

Thanks again!

   int k2 = -2147483648;

k2 = k2 >>> 1;

assertEquals(1073741824, k2); //this passes


//objective c generated code

   int _r34.i = -2147483648;

_r34.i = _r34.i >> (0x1f & 1);

   STAssertEquals(1073741824, _r34.i, @"Should be 1073741824 and not
-1073741824");

Re: [xmlvm-users] Rotate Right

[Troy G. <tro...@gm...>]

After further looking, it seems like the following would work for the
corresponding unsigned shift right >>> in Java to Objective C.

   int k = (unsigned) k >> (0x1f & 1);




On Fri, Nov 26, 2010 at 11:14 AM, Troy Gaines <tro...@gm...> wrote:

> From what I can tell, it looks like the objective C instruction might not
> always be the same when doing a shift right.  I posted the following Java
> code and corresponding Objective C code to illustrate this.  In Java the
> value ends up positive and Objective C negative.  I'm not sure if the left
> shift has this same issue.
>
> Thanks again!
>
> int k2 = -2147483648;
>
> k2 = k2 >>> 1;
>
> assertEquals(1073741824, k2); //this passes
>
>
> //objective c generated code
>
> int _r34.i = -2147483648;
>
> _r34.i = _r34.i >> (0x1f & 1);
>
> STAssertEquals(1073741824, _r34.i, @"Should be 1073741824 and not
> -1073741824");
>
>

Re: [xmlvm-users] Rotate Right

[Arno P. <ar...@pu...>]

you are right. There is a cast to an unsigned int missing for the ushr 
instruction. Should be fixed now.

Arno


On 11/26/10 9:50 AM, Troy Gaines wrote:
> After further looking, it seems like the following would work for the
> corresponding unsigned shift right >>> in Java to Objective C.
>
> int k = (unsigned) k >> (0x1f & 1);
>
>
>
>
> On Fri, Nov 26, 2010 at 11:14 AM, Troy Gaines <tro...@gm...
> <mailto:tro...@gm...>> wrote:
>
>      From what I can tell, it looks like the objective C instruction
>     might not always be the same when doing a shift right.  I posted the
>     following Java code and corresponding Objective C code to illustrate
>     this.  In Java the value ends up positive and Objective C negative.
>       I'm not sure if the left shift has this same issue.
>
>     Thanks again!
>
>     int k2 = -2147483648;
>
>     k2 = k2 >>> 1;
>
>     assertEquals(1073741824, k2); //this passes
>
>
>     //objective c generated code
>
>     int_r34.i = -2147483648;
>
>     _r34.i = _r34.i >> (0x1f & 1);
>
>     STAssertEquals(1073741824, _r34.i, @"Should be 1073741824 and not
>     -1073741824");
>
>
>
>
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