On Tue, Jul 19, 2016 at 12:24 PM, Ian Romanick <i...@freedesktop.org> wrote:
> From: Ian Romanick <ian.d.roman...@intel.com>
>
> (X & -X) calculates a value with only the least significant bit of X
> set. Since there is only one bit set, the LSB is the MSB.
>
> Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
> ---
> src/compiler/glsl/ir_constant_expression.cpp | 19 +++++++++----------
> 1 file changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/src/compiler/glsl/ir_constant_expression.cpp
> b/src/compiler/glsl/ir_constant_expression.cpp
> index 5f4cae2..71afb33 100644
> --- a/src/compiler/glsl/ir_constant_expression.cpp
> +++ b/src/compiler/glsl/ir_constant_expression.cpp
> @@ -1560,16 +1560,15 @@ ir_expression::constant_expression_value(struct
> hash_table *variable_context)
>
> case ir_unop_find_lsb:
> for (unsigned c = 0; c < components; c++) {
> - if (op[0]->value.i[c] == 0)
> - data.i[c] = -1;
> - else {
> - unsigned pos = 0;
> - unsigned v = op[0]->value.u[c];
> -
> - for (; !(v & 1); v >>= 1) {
> - pos++;
> - }
> - data.u[c] = pos;
> + switch (op[0]->type->base_type) {
> + case GLSL_TYPE_UINT:
> + data.i[c] = find_msb_uint(op[0]->value.u[c] &
> -int(op[0]->value.u[c]));
The int cast looks a bit weird (and unnecessary, right?)
I'd drop it unless there's a good reason to keep it.
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