diff options
| -rw-r--r-- | src/compiler/glsl/ir_constant_expression.cpp | 49 |
1 files changed, 34 insertions, 15 deletions
diff --git a/src/compiler/glsl/ir_constant_expression.cpp b/src/compiler/glsl/ir_constant_expression.cpp index a70c6600f5a..5376316d5df 100644 --- a/src/compiler/glsl/ir_constant_expression.cpp +++ b/src/compiler/glsl/ir_constant_expression.cpp @@ -494,6 +494,31 @@ bitfield_reverse(uint32_t v) return r; } +static int +find_msb_uint(uint32_t v) +{ + int count = 0; + + /* If v == 0, then the loop will terminate when count == 32. In that case + * 31-count will produce the -1 result required by GLSL findMSB(). + */ + while (((v & (1u << 31)) == 0) && count != 32) { + count++; + v <<= 1; + } + + return 31 - count; +} + +static int +find_msb_int(int32_t v) +{ + /* If v is signed, findMSB() returns the position of the most significant + * zero bit. + */ + return find_msb_uint(v < 0 ? ~v : v); +} + ir_constant * ir_expression::constant_expression_value(struct hash_table *variable_context) { @@ -1520,21 +1545,15 @@ ir_expression::constant_expression_value(struct hash_table *variable_context) case ir_unop_find_msb: for (unsigned c = 0; c < components; c++) { - int v = op[0]->value.i[c]; - - if (v == 0 || (op[0]->type->base_type == GLSL_TYPE_INT && v == -1)) - data.i[c] = -1; - else { - int count = 0; - unsigned top_bit = op[0]->type->base_type == GLSL_TYPE_UINT - ? 0 : v & (1u << 31); - - while (((v & (1u << 31)) == top_bit) && count != 32) { - count++; - v <<= 1; - } - - data.i[c] = 31 - count; + switch (op[0]->type->base_type) { + case GLSL_TYPE_UINT: + data.i[c] = find_msb_uint(op[0]->value.u[c]); + break; + case GLSL_TYPE_INT: + data.i[c] = find_msb_int(op[0]->value.i[c]); + break; + default: + assert(0); } } break; |