Fixed atan corner case
atan(0, <negative>) was returning 0 instead of PI. Did a simple
fix in the arctan() function and added an associated unit test.
Change-Id: Idbbdaf099b5104e3aaa2868ca8fd806c6c735981
Reviewed-on: https://swiftshader-review.googlesource.com/18868
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
diff --git a/src/Shader/ShaderCore.cpp b/src/Shader/ShaderCore.cpp
index 883131c..338605c 100644
--- a/src/Shader/ShaderCore.cpp
+++ b/src/Shader/ShaderCore.cpp
@@ -402,14 +402,13 @@
Float4 y0 = Abs(y);
// Rotate to right quadrant when in left quadrant
- Int4 non_zero_y = CmpNEQ(y0, Float4(0.0f));
- Int4 Q = CmpLT(x0, Float4(0.0f)) & non_zero_y;
+ Int4 Q = CmpLT(x0, Float4(0.0f));
theta += As<Float4>(Q & As<Int4>(half_pi));
Float4 x1 = As<Float4>((Q & As<Int4>(y0)) | (~Q & As<Int4>(x0))); // FIXME: Vector select
Float4 y1 = As<Float4>((Q & As<Int4>(-x0)) | (~Q & As<Int4>(y0))); // FIXME: Vector select
// Mirror to first octant when in second octant
- Int4 O = CmpNLT(y1, x1) & non_zero_y;
+ Int4 O = CmpNLT(y1, x1);
Float4 x2 = As<Float4>((O & As<Int4>(y1)) | (~O & As<Int4>(x1))); // FIXME: Vector select
Float4 y2 = As<Float4>((O & As<Int4>(x1)) | (~O & As<Int4>(y1))); // FIXME: Vector select
@@ -417,7 +416,7 @@
Int4 zero_x = CmpEQ(x2, Float4(0.0f));
Int4 inf_y = IsInf(y2); // Since x2 >= y2, this means x2 == y2 == inf, so we use 45 degrees or pi/4
Float4 atan2_theta = arctan_01(y2 / x2, pp);
- theta += As<Float4>((~zero_x & ~inf_y & non_zero_y & ((O & As<Int4>(half_pi - atan2_theta)) | (~O & (As<Int4>(atan2_theta))))) | // FIXME: Vector select
+ theta += As<Float4>((~zero_x & ~inf_y & ((O & As<Int4>(half_pi - atan2_theta)) | (~O & (As<Int4>(atan2_theta))))) | // FIXME: Vector select
(inf_y & As<Int4>(quarter_pi)));
// Recover loss of precision for tiny theta angles