diff options
| -rw-r--r-- | src/compiler/glsl/builtin_functions.cpp | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/src/compiler/glsl/builtin_functions.cpp b/src/compiler/glsl/builtin_functions.cpp index 432df656e2f..b8f9d8fe8ac 100644 --- a/src/compiler/glsl/builtin_functions.cpp +++ b/src/compiler/glsl/builtin_functions.cpp @@ -3604,11 +3604,31 @@ builtin_builder::_atan2(const glsl_type *type) body.emit(assign(rcp_scaled_t, rcp(mul(t, scale)))); ir_expression *s_over_t = mul(mul(s, scale), rcp_scaled_t); + /* For |x| = |y| assume tan = 1 even if infinite (i.e. pretend momentarily + * that ∞/∞ = 1) in order to comply with the rather artificial rules + * inherited from IEEE 754-2008, namely: + * + * "atan2(±∞, −∞) is ±3π/4 + * atan2(±∞, +∞) is ±π/4" + * + * Note that this is inconsistent with the rules for the neighborhood of + * zero that are based on iterated limits: + * + * "atan2(±0, −0) is ±π + * atan2(±0, +0) is ±0" + * + * but GLSL specifically allows implementations to deviate from IEEE rules + * at (0,0), so we take that license (i.e. pretend that 0/0 = 1 here as + * well). + */ + ir_expression *tan = csel(equal(abs(x), abs(y)), + imm(1.0f, n), abs(s_over_t)); + /* Calculate the arctangent and fix up the result if we had flipped the * coordinate system. */ ir_variable *arc = body.make_temp(type, "arc"); - do_atan(body, type, arc, abs(s_over_t)); + do_atan(body, type, arc, tan); body.emit(assign(arc, add(arc, mul(b2f(flip), imm(M_PI_2f))))); /* Rather convoluted calculation of the sign of the result. When x < 0 we |