[Piglit] [PATCH] CL Builtins: Fix sign-extension bug in rotate

[Tom Stellard]

On Sat, Mar 23, 2013 at 12:06:53PM -0500, Aaron Watry wrote:
> When rotating a negative number right, sign extension was producing the wrong
> expected result.

Reviewed-by: Tom Stellard <thomas.stellard at amd.com>

> ---
>  generated_tests/generate-cl-int-builtins.py |   17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/generated_tests/generate-cl-int-builtins.py b/generated_tests/generate-cl-int-builtins.py
> index 2460594..56abbc7 100755
> --- a/generated_tests/generate-cl-int-builtins.py
> +++ b/generated_tests/generate-cl-int-builtins.py
> @@ -196,9 +196,16 @@ def pow(val,pow):
>      return val ** pow
>  
>  def rotate_right(x, n, bits):
> +    #Find all bits that will wrap
>      mask = (2L**n) - 1
> -    mask_bits = x & mask
> -    return (x >> n) | (mask_bits << (bits - n))
> +    wrapped_bits = x & mask
> +
> +    #sign extension needs to be masked out
> +    se_mask = (1 << (bits - n)) - 1;
> +    unwrapped_bits = x >> n;
> +    unwrapped_bits &= se_mask;
> +
> +    return unwrapped_bits | (wrapped_bits << (bits - n))
>  
>  def rotate_left(x, n, bits):
>      return rotate_right(x, bits - n, bits)
> @@ -518,11 +525,11 @@ signed_generic_tests = {
>          'function_type': 'ttt',
>          'values': [
>              [         MIN, MIN, [rot,1,-3,SIZE],             1,
> -                      MIN,  [pow,2,[sub,SIZE,2]],          MIN],
> +                      MIN,  [pow,2,[sub,SIZE,2]],          MIN, [rot,-2,-1,SIZE]],
>              [           1,   1,               1,             1,
> -                        1,                     1,            1],
> +                        1,                     1,            1, -2],
>              [[sub,SIZE,1],  -1,              -3, [mul,SIZE,-1],
> -             [mul,[add,SIZE,1],-1], [mul,[add,SIZE,2],-1], [sub,SIZE,1]]
> +             [mul,[add,SIZE,1],-1], [mul,[add,SIZE,2],-1], [sub,SIZE,1], -1]
>          ]
>      },
>      'sub_sat': {
> -- 
> 1.7.10.4
> 
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