Macros to eliminate 'f + 0.0' (#21568)

Marlin/src/core/macros.h

 #define DISABLED(V...)      DO(DIS,&&,V)
 #define COUNT_ENABLED(V...) DO(ENA,+,V)
 
-#define TERN(O,A,B)         _TERN(_ENA_1(O),B,A)    // OPTION converted to '0' or '1'
-#define TERN0(O,A)          _TERN(_ENA_1(O),0,A)    // OPTION converted to A or '0'
-#define TERN1(O,A)          _TERN(_ENA_1(O),1,A)    // OPTION converted to A or '1'
-#define TERN_(O,A)          _TERN(_ENA_1(O),,A)     // OPTION converted to A or '<nul>'
+#define TERN(O,A,B)         _TERN(_ENA_1(O),B,A)    // OPTION ? 'A' : 'B'
+#define TERN0(O,A)          _TERN(_ENA_1(O),0,A)    // OPTION ? 'A' : '0'
+#define TERN1(O,A)          _TERN(_ENA_1(O),1,A)    // OPTION ? 'A' : '1'
+#define TERN_(O,A)          _TERN(_ENA_1(O),,A)     // OPTION ? 'A' : '<nul>'
 #define _TERN(E,V...)       __TERN(_CAT(T_,E),V)    // Prepend 'T_' to get 'T_0' or 'T_1'
 #define __TERN(T,V...)      ___TERN(_CAT(_NO,T),V)  // Prepend '_NO' to get '_NOT_0' or '_NOT_1'
 #define ___TERN(P,V...)     THIRD(P,V)              // If first argument has a comma, A. Else B.
 
+// Macros to avoid 'f + 0.0' which is not always optimized away. Minus included for symmetry.
+// Compiler flags -fno-signed-zeros -ffinite-math-only also cover 'f * 1.0', 'f - f', etc.
+#define PLUS_TERN0(O,A)     _TERN(_ENA_1(O),,+ (A)) // OPTION ? '+ (A)' : '<nul>'
+#define MINUS_TERN0(O,A)    _TERN(_ENA_1(O),,- (A)) // OPTION ? '- (A)' : '<nul>'
+#define SUM_TERN(O,B,A)     ((B) PLUS_TERN0(O,A))   // ((B) (OPTION ? '+ (A)' : '<nul>'))
+#define DIFF_TERN(O,B,A)    ((B) MINUS_TERN0(O,A))  // ((B) (OPTION ? '- (A)' : '<nul>'))
+
 #define IF_ENABLED          TERN_
 #define IF_DISABLED(O,A)    TERN(O,,A)
 

Marlin/src/gcode/bedlevel/G35.cpp

     // In BLTOUCH HS mode, the probe travels in a deployed state.
     // Users of G35 might have a badly misaligned bed, so raise Z by the
     // length of the deployed pin (BLTOUCH stroke < 7mm)
-    do_blocking_move_to_z((Z_CLEARANCE_BETWEEN_PROBES) + TERN0(BLTOUCH_HS_MODE, 7));
+    do_blocking_move_to_z(SUM_TERN(BLTOUCH_HS_MODE, Z_CLEARANCE_BETWEEN_PROBES, 7));
     const float z_probed_height = probe.probe_at_point(screws_tilt_adjust_pos[i], PROBE_PT_RAISE, 0, true);
 
     if (isnan(z_probed_height)) {

Marlin/src/lcd/menu/menu_bed_corners.cpp

     do {
       ui.refresh(LCDVIEW_REDRAW_NOW);
       _lcd_draw_probing();                                             // update screen with # of good points
-      do_blocking_move_to_z(current_position.z + LEVEL_CORNERS_Z_HOP + TERN0(BLTOUCH_HS_MODE, 7)); // clearance
+      do_blocking_move_to_z(SUM_TERN(BLTOUCH_HS_MODE, current_position.z + LEVEL_CORNERS_Z_HOP, 7)); // clearance
 
       _lcd_level_bed_corners_get_next_position();         // Select next corner coordinates
       current_position -= probe.offset_xy;                // Account for probe offsets

Marlin/src/lcd/menu/menu_motion.cpp

   ui.encoderPosition = 0;
   if (ui.should_draw()) {
     const float pos = NATIVE_TO_LOGICAL(
-      ui.manual_move.processing ? destination[axis] : current_position[axis] + TERN0(IS_KINEMATIC, ui.manual_move.offset),
+      ui.manual_move.processing ? destination[axis] : SUM_TERN(IS_KINEMATIC, current_position[axis], ui.manual_move.offset),
       axis
     );
     if (parser.using_inch_units()) {
       MenuEditItemBase::draw_edit_screen(
         GET_TEXT(TERN(MULTI_MANUAL, MSG_MOVE_EN, MSG_MOVE_E)),
         ftostr41sign(current_position.e
-          + TERN0(IS_KINEMATIC, ui.manual_move.offset)
-          - TERN0(MANUAL_E_MOVES_RELATIVE, manual_move_e_origin)
+          PLUS_TERN0(IS_KINEMATIC, ui.manual_move.offset)
+          MINUS_TERN0(MANUAL_E_MOVES_RELATIVE, manual_move_e_origin)
         )
       );
     } // should_draw

Marlin/src/lcd/tft/ui_480x320.cpp

       probe.offset.z :
     #endif
     NATIVE_TO_LOGICAL(
-      ui.manual_move.processing ? destination[axis] : current_position[axis] + TERN0(IS_KINEMATIC, ui.manual_move.offset),
+      ui.manual_move.processing ? destination[axis] : SUM_TERN(IS_KINEMATIC, current_position[axis], ui.manual_move.offset),
       axis
     );
   xy_int_t pos;

Marlin/src/module/delta.cpp

   #endif
 
   // Move all carriages together linearly until an endstop is hit.
-  current_position.z = (delta_height + 10 - TERN0(HAS_BED_PROBE, probe.offset.z));
+  current_position.z = DIFF_TERN(HAS_BED_PROBE, delta_height + 10, probe.offset.z);
   line_to_current_position(homing_feedrate(Z_AXIS));
   planner.synchronize();
 

Marlin/src/module/motion.cpp

     #elif ENABLED(DELTA)
 
       soft_endstop.min[axis] = base_min_pos(axis);
-      soft_endstop.max[axis] = (axis == Z_AXIS) ? delta_height - TERN0(HAS_BED_PROBE, probe.offset.z) : base_max_pos(axis);
+      soft_endstop.max[axis] = (axis == Z_AXIS) ? DIFF_TERN(HAS_BED_PROBE, delta_height, probe.offset.z) : base_max_pos(axis);
 
       switch (axis) {
         case X_AXIS:
   #if EITHER(MORGAN_SCARA, AXEL_TPARA)
     scara_set_axis_is_at_home(axis);
   #elif ENABLED(DELTA)
-    current_position[axis] = (axis == Z_AXIS) ? delta_height - TERN0(HAS_BED_PROBE, probe.offset.z) : base_home_pos(axis);
+    current_position[axis] = (axis == Z_AXIS) ? DIFF_TERN(HAS_BED_PROBE, delta_height, probe.offset.z) : base_home_pos(axis);
   #else
     current_position[axis] = base_home_pos(axis);
   #endif

Marlin/src/module/planner.cpp

   const uint8_t axis_index = E_AXIS_N(active_extruder);
   TERN_(DISTINCT_E_FACTORS, last_extruder = active_extruder);
 
-  const float e_new = e - TERN0(FWRETRACT, fwretract.current_retract[active_extruder]);
+  const float e_new = DIFF_TERN(FWRETRACT, e, fwretract.current_retract[active_extruder]);
   position.e = LROUND(settings.axis_steps_per_mm[axis_index] * e_new);
   TERN_(HAS_POSITION_FLOAT, position_float.e = e_new);
   TERN_(IS_KINEMATIC, position_cart.e = e);

Marlin/src/module/scara.cpp

   void forward_kinematics(const_float_t a, const_float_t b) {
     const float a_sin = sin(RADIANS(a)) * L1,
                 a_cos = cos(RADIANS(a)) * L1,
-                b_sin = sin(RADIANS(b + TERN0(MP_SCARA, a))) * L2,
-                b_cos = cos(RADIANS(b + TERN0(MP_SCARA, a))) * L2;
+                b_sin = sin(RADIANS(SUM_TERN(MP_SCARA, b, a))) * L2,
+                b_cos = cos(RADIANS(SUM_TERN(MP_SCARA, b, a))) * L2;
 
     cartes.x = a_cos + b_cos + scara_offset.x;  // theta
     cartes.y = a_sin + b_sin + scara_offset.y;  // phi
     // Angle of Arm2
     PSI = ATAN2(S2, C2);
 
-    delta.set(DEGREES(THETA), DEGREES(PSI + TERN0(MORGAN_SCARA, THETA)), raw.z);
+    delta.set(DEGREES(THETA), DEGREES(SUM_TERN(MORGAN_SCARA, PSI, THETA)), raw.z);
 
     /*
       DEBUG_POS("SCARA IK", raw);

Marlin/src/module/tool_change.cpp

 
       // STEP 6
 
-      current_position.x = midpos - TERN0(HAS_HOTEND_OFFSET, hotend_offset[new_tool].x);
+      current_position.x = DIFF_TERN(HAS_HOTEND_OFFSET, midpos, hotend_offset[new_tool].x);
 
       DEBUG_SYNCHRONIZE();
       DEBUG_POS("(6) Move midway between hotends", current_position);