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glsl: Add support for constant expression evaluation on round(), roundEven().

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v2: Avoid the C99 rounding functions, because I don't trust
get/setting the C99 rounding mode from inside our library not having
other side effects.  Instead, open-code roundEven() behavior around
Mesa's IROUND, which we're already testing for C99 rounding mode
safety.

Fixes glsl-1.30/compiler/built-in-functions/round*

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Eric Anholt 2011-09-27 14:54:10 -07:00
parent b27a67af89
commit dc637b66b2
1 changed files with 29 additions and 0 deletions
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29
src/glsl/ir_constant_expression.cpp
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@ -39,6 +39,25 @@
#include "ir_visitor.h"
#include "glsl_types.h"
/* Using C99 rounding functions for roundToEven() implementation is
* difficult, because round(), rint, and nearbyint() are affected by
* fesetenv(), which the application may have done for its own
* purposes. Mesa's IROUND macro is close to what we want, but it
* rounds away from 0 on n + 0.5.
*/
static int
round_to_even(float val)
{
int rounded = IROUND(val);
if (val - floor(val) == 0.5) {
if (rounded % 2 != 0)
rounded += val > 0 ? -1 : 1;
}
return rounded;
}
static float
dot(ir_constant *op0, ir_constant *op1)
{
@ -196,6 +215,13 @@ ir_expression::constant_expression_value()
}
break;
case ir_unop_round_even:
assert(op[0]->type->base_type == GLSL_TYPE_FLOAT);
for (unsigned c = 0; c < op[0]->type->components(); c++) {
data.f[c] = round_to_even(op[0]->value.f[c]);
}
break;
case ir_unop_ceil:
assert(op[0]->type->base_type == GLSL_TYPE_FLOAT);
for (unsigned c = 0; c < op[0]->type->components(); c++) {
@ -1324,6 +1350,9 @@ ir_call::constant_expression_value()
* op[1]->value.f[c];
}
}
} else if (strcmp(callee, "round") == 0 ||
strcmp(callee, "roundEven") == 0) {
expr = new(mem_ctx) ir_expression(ir_unop_round_even, op[0]);
} else if (strcmp(callee, "sign") == 0) {
expr = new(mem_ctx) ir_expression(ir_unop_sign, type, op[0], NULL);
} else if (strcmp(callee, "sin") == 0) {