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vc4: Improve the accuracy of SIN and COS.

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This gets them to pass glsl-sin/cos.  There was an obvious problem that I
was using the FRC code on the scaled input value, which means that we had
a range in [0, 1], while our taylor is most accurate across [-0.5, 0.5].
We can just slide things over, but that means flipping the sign of the
coefficients.  After that, it was just a matter of stuffing more
coefficients in.
This commit is contained in:
Eric Anholt 2014-10-13 14:11:28 +01:00
parent 02ca66fbc3
commit 5bc91b6e32
1 changed files with 17 additions and 11 deletions
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28
src/gallium/drivers/vc4/vc4_program.c
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@ -766,10 +766,11 @@ tgsi_to_qir_sin(struct vc4_compile *c,
enum qop op, struct qreg *src, int i)
{
float coeff[] = {
2.0 * M_PI,
-pow(2.0 * M_PI, 3) / (3 * 2 * 1),
pow(2.0 * M_PI, 5) / (5 * 4 * 3 * 2 * 1),
-pow(2.0 * M_PI, 7) / (7 * 6 * 5 * 4 * 3 * 2 * 1),
-2.0 * M_PI,
pow(2.0 * M_PI, 3) / (3 * 2 * 1),
-pow(2.0 * M_PI, 5) / (5 * 4 * 3 * 2 * 1),
pow(2.0 * M_PI, 7) / (7 * 6 * 5 * 4 * 3 * 2 * 1),
-pow(2.0 * M_PI, 9) / (9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1),
};
struct qreg scaled_x =
@ -777,8 +778,9 @@ tgsi_to_qir_sin(struct vc4_compile *c,
src[0 * 4 + 0],
qir_uniform_f(c, 1.0f / (M_PI * 2.0f)));
struct qreg x = tgsi_to_qir_frc(c, NULL, 0, &scaled_x, 0);
struct qreg x = qir_FADD(c,
tgsi_to_qir_frc(c, NULL, 0, &scaled_x, 0),
qir_uniform_f(c, -0.5));
struct qreg x2 = qir_FMUL(c, x, x);
struct qreg sum = qir_FMUL(c, x, qir_uniform_f(c, coeff[0]));
for (int i = 1; i < ARRAY_SIZE(coeff); i++) {
@ -799,16 +801,20 @@ tgsi_to_qir_cos(struct vc4_compile *c,
enum qop op, struct qreg *src, int i)
{
float coeff[] = {
1.0f,
-pow(2.0 * M_PI, 2) / (2 * 1),
pow(2.0 * M_PI, 4) / (4 * 3 * 2 * 1),
-pow(2.0 * M_PI, 6) / (6 * 5 * 4 * 3 * 2 * 1),
-1.0f,
pow(2.0 * M_PI, 2) / (2 * 1),
-pow(2.0 * M_PI, 4) / (4 * 3 * 2 * 1),
pow(2.0 * M_PI, 6) / (6 * 5 * 4 * 3 * 2 * 1),
-pow(2.0 * M_PI, 8) / (8 * 7 * 6 * 5 * 4 * 3 * 2 * 1),
pow(2.0 * M_PI, 10) / (10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1),
};
struct qreg scaled_x =
qir_FMUL(c, src[0 * 4 + 0],
qir_uniform_f(c, 1.0f / (M_PI * 2.0f)));
struct qreg x_frac = tgsi_to_qir_frc(c, NULL, 0, &scaled_x, 0);
struct qreg x_frac = qir_FADD(c,
tgsi_to_qir_frc(c, NULL, 0, &scaled_x, 0),
qir_uniform_f(c, -0.5));
struct qreg sum = qir_uniform_f(c, coeff[0]);
struct qreg x2 = qir_FMUL(c, x_frac, x_frac);