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]));
+ break;
+ case GLSL_TYPE_INT:
+ data.i[c] = find_msb_uint(op[0]->value.i[c] & -op[0]->value.i[c]);
+ break;
+ default:
+ assert(0);
}
}
break;
--
2.5.5
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/mesa-dev
