glsl: lower double optional passes (v2)

These lowering passes are optional for the backend to request, currently
the TGSI softpipe backend most likely the r600g backend would want to use
these passes as is. They aim to hit the gallium opcodes from the standard
rounding/truncation functions.

v2: also lower floor in mod_to_floor

Signed-off-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>

1 files changed, 175 insertions, 0 deletions

diff --git a/src/glsl/lower_instructions.cpp b/src/glsl/lower_instructions.cpp
index 8994aad..c63c018 100644
--- a/src/glsl/lower_instructions.cpp
+++ b/src/glsl/lower_instructions.cpp
@@ -42,6 +42,7 @@
  * - CARRY_TO_ARITH
  * - BORROW_TO_ARITH
  * - SAT_TO_CLAMP
+ * - DOPS_TO_DFRAC
  *
  * SUB_TO_ADD_NEG:
  * ---------------
@@ -112,6 +113,9 @@
  * -------------
  * Converts ir_unop_saturate into min(max(x, 0.0), 1.0)
  *
+ * DOPS_TO_DFRAC:
+ * --------------
+ * Converts double trunc, ceil, floor, round to fract
  */
 
 #include "main/core.h" /* for M_LOG2E */
@@ -151,6 +155,11 @@ private:
    void sat_to_clamp(ir_expression *);
    void double_dot_to_fma(ir_expression *);
    void double_lrp(ir_expression *);
+   void dceil_to_dfrac(ir_expression *);
+   void dfloor_to_dfrac(ir_expression *);
+   void dround_even_to_dfrac(ir_expression *);
+   void dtrunc_to_dfrac(ir_expression *);
+   void dsign_to_csel(ir_expression *);
 };
 
 } /* anonymous namespace */
@@ -315,6 +324,9 @@ lower_instructions_visitor::mod_to_floor(ir_expression *ir)
    ir_expression *const floor_expr =
       new(ir) ir_expression(ir_unop_floor, x->type, div_expr);
 
+   if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
+      dfloor_to_dfrac(floor_expr);
+
    ir_expression *const mul_expr =
       new(ir) ir_expression(ir_binop_mul,
                             new(ir) ir_dereference_variable(y),
@@ -578,6 +590,145 @@ lower_instructions_visitor::double_lrp(ir_expression *ir)
    this->progress = true;
 }
 
+void
+lower_instructions_visitor::dceil_to_dfrac(ir_expression *ir)
+{
+   /*
+    * frtemp = frac(x);
+    * temp = sub(x, frtemp);
+    * result = temp + ((frtemp != 0.0) ? 1.0 : 0.0);
+    */
+   ir_instruction &i = *base_ir;
+   ir_constant *zero = new(ir) ir_constant(0.0, ir->operands[0]->type->vector_elements);
+   ir_constant *one = new(ir) ir_constant(1.0, ir->operands[0]->type->vector_elements);
+   ir_variable *frtemp = new(ir) ir_variable(ir->operands[0]->type, "frtemp",
+                                             ir_var_temporary);
+
+   i.insert_before(frtemp);
+   i.insert_before(assign(frtemp, fract(ir->operands[0])));
+
+   ir->operation = ir_binop_add;
+   ir->operands[0] = sub(ir->operands[0]->clone(ir, NULL), frtemp);
+   ir->operands[1] = csel(nequal(frtemp, zero), one, zero->clone(ir, NULL));
+
+   this->progress = true;
+}
+
+void
+lower_instructions_visitor::dfloor_to_dfrac(ir_expression *ir)
+{
+   /*
+    * frtemp = frac(x);
+    * result = sub(x, frtemp);
+    */
+   ir->operation = ir_binop_sub;
+   ir->operands[1] = fract(ir->operands[0]->clone(ir, NULL));
+
+   this->progress = true;
+}
+void
+lower_instructions_visitor::dround_even_to_dfrac(ir_expression *ir)
+{
+   /*
+    * insane but works
+    * temp = x + 0.5;
+    * frtemp = frac(temp);
+    * t2 = sub(temp, frtemp);
+    * if (frac(x) == 0.5)
+    *     result = frac(t2 * 0.5) == 0 ? t2 : t2 - 1;
+    *  else
+    *     result = t2;
+
+    */
+   ir_instruction &i = *base_ir;
+   ir_variable *frtemp = new(ir) ir_variable(ir->operands[0]->type, "frtemp",
+                                             ir_var_temporary);
+   ir_variable *temp = new(ir) ir_variable(ir->operands[0]->type, "temp",
+                                           ir_var_temporary);
+   ir_variable *t2 = new(ir) ir_variable(ir->operands[0]->type, "t2",
+                                           ir_var_temporary);
+   ir_constant *p5 = new(ir) ir_constant(0.5, ir->operands[0]->type->vector_elements);
+   ir_constant *one = new(ir) ir_constant(1.0, ir->operands[0]->type->vector_elements);
+   ir_constant *zero = new(ir) ir_constant(0.0, ir->operands[0]->type->vector_elements);
+
+   i.insert_before(temp);
+   i.insert_before(assign(temp, add(ir->operands[0], p5)));
+
+   i.insert_before(frtemp);
+   i.insert_before(assign(frtemp, fract(temp)));
+
+   i.insert_before(t2);
+   i.insert_before(assign(t2, sub(temp, frtemp)));
+
+   ir->operation = ir_triop_csel;
+   ir->operands[0] = equal(fract(ir->operands[0]->clone(ir, NULL)),
+                           p5->clone(ir, NULL));
+   ir->operands[1] = csel(equal(fract(mul(t2, p5->clone(ir, NULL))),
+                                zero),
+                          t2,
+                          sub(t2, one));
+   ir->operands[2] = new(ir) ir_dereference_variable(t2);
+
+   this->progress = true;
+}
+
+void
+lower_instructions_visitor::dtrunc_to_dfrac(ir_expression *ir)
+{
+   /*
+    * frtemp = frac(x);
+    * temp = sub(x, frtemp);
+    * result = x >= 0 ? temp : temp + (frtemp == 0.0) ? 0 : 1;
+    */
+   ir_rvalue *arg = ir->operands[0];
+   ir_instruction &i = *base_ir;
+
+   ir_constant *zero = new(ir) ir_constant(0.0, arg->type->vector_elements);
+   ir_constant *one = new(ir) ir_constant(1.0, arg->type->vector_elements);
+   ir_variable *frtemp = new(ir) ir_variable(arg->type, "frtemp",
+                                             ir_var_temporary);
+   ir_variable *temp = new(ir) ir_variable(ir->operands[0]->type, "temp",
+                                           ir_var_temporary);
+
+   i.insert_before(frtemp);
+   i.insert_before(assign(frtemp, fract(arg)));
+   i.insert_before(temp);
+   i.insert_before(assign(temp, sub(arg->clone(ir, NULL), frtemp)));
+
+   ir->operation = ir_triop_csel;
+   ir->operands[0] = gequal(arg->clone(ir, NULL), zero);
+   ir->operands[1] = new (ir) ir_dereference_variable(temp);
+   ir->operands[2] = add(temp,
+                         csel(equal(frtemp, zero->clone(ir, NULL)),
+                              zero->clone(ir, NULL),
+                              one));
+
+   this->progress = true;
+}
+
+void
+lower_instructions_visitor::dsign_to_csel(ir_expression *ir)
+{
+   /*
+    * temp = x > 0.0 ? 1.0 : 0.0;
+    * result = x < 0.0 ? -1.0 : temp;
+    */
+   ir_rvalue *arg = ir->operands[0];
+   ir_constant *zero = new(ir) ir_constant(0.0, arg->type->vector_elements);
+   ir_constant *one = new(ir) ir_constant(1.0, arg->type->vector_elements);
+   ir_constant *neg_one = new(ir) ir_constant(-1.0, arg->type->vector_elements);
+
+   ir->operation = ir_triop_csel;
+   ir->operands[0] = less(arg->clone(ir, NULL),
+                          zero->clone(ir, NULL));
+   ir->operands[1] = neg_one;
+   ir->operands[2] = csel(greater(arg, zero),
+                          one,
+                          zero->clone(ir, NULL));
+
+   this->progress = true;
+}
+
 ir_visitor_status
 lower_instructions_visitor::visit_leave(ir_expression *ir)
 {
@@ -647,6 +798,30 @@ lower_instructions_visitor::visit_leave(ir_expression *ir)
          sat_to_clamp(ir);
       break;
 
+   case ir_unop_trunc:
+      if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
+         dtrunc_to_dfrac(ir);
+      break;
+
+   case ir_unop_ceil:
+      if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
+         dceil_to_dfrac(ir);
+      break;
+
+   case ir_unop_floor:
+      if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
+         dfloor_to_dfrac(ir);
+      break;
+
+   case ir_unop_round_even:
+      if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
+         dround_even_to_dfrac(ir);
+      break;
+
+   case ir_unop_sign:
+      if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
+         dsign_to_csel(ir);
+      break;
    default:
       return visit_continue;
    }