[Mesa-dev] [PATCH 44/47] glsl: Add a lowering pass for 64-bit float floor()

[Elie Tournier]

Signed-off-by: Elie Tournier <elie.tournier at collabora.com>
---
 src/compiler/glsl/ir_optimization.h        |  1 +
 src/compiler/glsl/lower_instructions.cpp   | 34 ++++++++++++++++++++++++++++--
 src/mesa/state_tracker/st_glsl_to_tgsi.cpp |  2 +-
 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/src/compiler/glsl/ir_optimization.h b/src/compiler/glsl/ir_optimization.h
index a2ebc16e93..f004380670 100644
--- a/src/compiler/glsl/ir_optimization.h
+++ b/src/compiler/glsl/ir_optimization.h
@@ -55,6 +55,7 @@
 #define DIV_TO_MUL_RCP            (FDIV_TO_MUL_RCP | DDIV_TO_MUL_RCP)
 #define SQRT_TO_ABS_SQRT          0x200000
 #define MIN_MAX_TO_LESS           0x400000
+#define DOPS_TO_DTRUNC            0x800000
 
 /* Operations for lower_64bit_integer_instructions()
  * and lower_64bit_double_instructions()
diff --git a/src/compiler/glsl/lower_instructions.cpp b/src/compiler/glsl/lower_instructions.cpp
index c6c3a627d3..50c35124fb 100644
--- a/src/compiler/glsl/lower_instructions.cpp
+++ b/src/compiler/glsl/lower_instructions.cpp
@@ -44,6 +44,7 @@
  * - SAT_TO_CLAMP
  * - DOPS_TO_DFRAC
  * - MIN_MAX_TO_LESS
+ * - DOPS_TO_DTRUNC
  *
  * SUB_TO_ADD_NEG:
  * ---------------
@@ -178,6 +179,7 @@ private:
    void sqrt_to_abs_sqrt(ir_expression *ir);
    void min_to_less(ir_expression *ir);
    void max_to_less(ir_expression *ir);
+   void dfloor_to_dtrunc(ir_expression *ir);
 
    ir_expression *_carry(operand a, operand b);
 };
@@ -1660,6 +1662,29 @@ lower_instructions_visitor::max_to_less(ir_expression *ir)
    this->progress = true;
 }
 
+void
+lower_instructions_visitor::dfloor_to_dtrunc(ir_expression *ir)
+{
+   /*
+    * For x >= 0, floor(x) = trunc(x)
+    * For x < 0,
+    *    - if x is integer, floor(x) = x
+    *    - otherwise, floor(x) = trunc(x) - 1
+    */
+
+   ir_rvalue *src = ir->operands[0]->clone(ir, NULL);
+   ir_rvalue *tr = trunc(src);
+
+   ir->operation = ir_triop_csel;
+   ir->init_num_operands();
+   ir->operands[0] = logic_or(gequal(src, new(ir) ir_constant(0.0, 1)),
+                              equal(src, tr));
+   ir->operands[1] = tr;
+   ir->operands[2] = add(tr, new(ir) ir_constant(-1.0, 1));
+
+   this->progress = true;
+}
+
 ir_visitor_status
 lower_instructions_visitor::visit_leave(ir_expression *ir)
 {
@@ -1748,8 +1773,13 @@ lower_instructions_visitor::visit_leave(ir_expression *ir)
       break;
 
    case ir_unop_floor:
-      if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
-         dfloor_to_dfrac(ir);
+      if (ir->type->is_double()) {
+         if (lowering(DOPS_TO_DFRAC)) {
+            dfloor_to_dfrac(ir);
+         } else if (lowering(DOPS_TO_DTRUNC) && ir->type->is_scalar()) {
+            dfloor_to_dtrunc(ir);
+         }
+      }
       break;
 
    case ir_unop_round_even:
diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index ef3a15932a..4fbf2c0a99 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -7058,7 +7058,7 @@ st_link_shader(struct gl_context *ctx, struct gl_shader_program *prog)
        */
       if (!pscreen->get_param(pscreen, PIPE_CAP_DOUBLES) &&
             ctx->Const.GLSLVersion >= 130) {
-         lower_instructions(ir, MIN_MAX_TO_LESS);
+         lower_instructions(ir, MIN_MAX_TO_LESS | DOPS_TO_DTRUNC);
          unsigned lower_inst = ABS64 |
                                NEG64 |
                                SIGN64 |
-- 
2.14.1