agx: Implement fsin/fcos

First, we lower to fsin_agx and some ALU in NIR. Then, we implement
fsin_agx with the underlying transcental ops.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Acked-by: Jason Ekstrand <jason@jlekstrand.net>
Acked-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10582>

src/asahi/compiler/agx_compile.c

@@ -257,6 +257,13 @@ agx_emit_alu(agx_builder *b, nir_alu_instr *instr)
       return I;
    }
 
+   case nir_op_fsin_agx:
+   {
+      agx_index fixup = agx_sin_pt_1(b, s0);
+      agx_index sinc = agx_sin_pt_2(b, fixup);
+      return agx_fmul_to(b, dst, sinc, fixup);
+   }
+
    case nir_op_vec2:
    case nir_op_vec3:
    case nir_op_vec4:
@@ -403,6 +410,46 @@ glsl_type_size(const struct glsl_type *type, bool bindless)
    return glsl_count_attribute_slots(type, false);
 }
 
+static bool
+agx_lower_sincos_filter(const nir_instr *instr, UNUSED const void *_)
+{
+   if (instr->type != nir_instr_type_alu)
+      return false;
+
+   nir_alu_instr *alu = nir_instr_as_alu(instr);
+   return alu->op == nir_op_fsin || alu->op == nir_op_fcos;
+}
+
+/* Sine and cosine are implemented via the sin_pt_1 and sin_pt_2 opcodes for
+ * heavy lifting. sin_pt_2 implements sinc in the first quadrant, expressed in
+ * turns (sin (tau x) / x), while sin_pt_1 implements a piecewise sign/offset
+ * fixup to transform a quadrant angle [0, 4] to [-1, 1]. The NIR opcode
+ * fsin_agx models the fixup, sinc, and multiply to obtain sine, so we just
+ * need to change units from radians to quadrants modulo turns. Cosine is
+ * implemented by shifting by one quadrant: cos(x) = sin(x + tau/4).
+ */
+
+static nir_ssa_def *
+agx_lower_sincos_impl(struct nir_builder *b, nir_instr *instr, UNUSED void *_)
+{
+   nir_alu_instr *alu = nir_instr_as_alu(instr);
+   nir_ssa_def *x = nir_mov_alu(b, alu->src[0], 1);
+   nir_ssa_def *turns = nir_fmul_imm(b, x, M_1_PI * 0.5f);
+
+   if (alu->op == nir_op_fcos)
+      turns = nir_fadd_imm(b, turns, 0.25f);
+
+   nir_ssa_def *quadrants = nir_fmul_imm(b, nir_ffract(b, turns), 4.0);
+   return nir_fsin_agx(b, quadrants);
+}
+
+static bool
+agx_lower_sincos(nir_shader *shader)
+{
+   return nir_shader_lower_instructions(shader,
+         agx_lower_sincos_filter, agx_lower_sincos_impl, NULL);
+}
+
 static void
 agx_optimize_nir(nir_shader *nir)
 {
@@ -419,6 +466,7 @@ agx_optimize_nir(nir_shader *nir)
    NIR_PASS_V(nir, nir_lower_alu_to_scalar, NULL, NULL);
    NIR_PASS_V(nir, nir_lower_load_const_to_scalar);
    NIR_PASS_V(nir, nir_lower_flrp, 16 | 32 | 64, false);
+   NIR_PASS_V(nir, agx_lower_sincos);
 
    do {
       progress = false;