Avoid runtime floats in Pulley::PlanMove

Using U_mm inside a compilation unit will force the compiler to generate
a runtime copy of the function, and we don't want that.

But there seems also to be an optimization problem with gcc <= 7.x where
even when declaring an inline function constexpr, if called enough
times, the compiler will choose _not_ to evaluate the function at
compile time and thus avoid our compile-time float->integer
conversions...

For this reason, split the body of the function in two parts: the actual
function that uses AxisUnits at runtime for calling motion.PlanMove, and
a wrapper that forces the conversion. By marking this function as
always_inline, the body is correctly evaluated at compile time at each
call site.

src/modules/pulley.cpp

@@ -3,7 +3,6 @@
 #include "buttons.h"
 #include "globals.h"
 #include "leds.h"
-#include "motion.h"
 #include "permanent_storage.h"
 #include "../debug.h"
 
@@ -34,7 +33,7 @@ bool Pulley::Step() {
     }
 }
 
-void Pulley::PlanMove(unit::U_mm delta, unit::U_mm_s feed_rate, unit::U_mm_s end_rate) {
+void Pulley::PlanMove(mm::P_pos_t delta, mm::P_speed_t feed_rate, mm::P_speed_t end_rate) {
     mm::motion.PlanMove<mm::Pulley>(delta, feed_rate, end_rate);
     state = Moving;
 }

src/modules/pulley.h

@@ -1,9 +1,8 @@
 /// @file pulley.h
 #pragma once
 #include "../config/config.h"
-#include "axisunit.h"
-#include "../unit.h"
 #include "movable_base.h"
+#include "motion.h"
 
 namespace modules {
 
@@ -25,7 +24,14 @@ public:
     /// @returns true if the pulley is ready to accept new commands (i.e. it has finished the last operation)
     bool Step();
 
-    void PlanMove(unit::U_mm delta, unit::U_mm_s feed_rate, unit::U_mm_s end_rate = { 0 });
+    void PlanMove(mm::P_pos_t delta, mm::P_speed_t feed_rate, mm::P_speed_t end_rate = { 0 });
+
+    // NOTE: always_inline is required here to force gcc <= 7.x to evaluate each call at compile time
+    void __attribute__((always_inline)) PlanMove(unit::U_mm delta, unit::U_mm_s feed_rate, unit::U_mm_s end_rate = { 0 }) {
+        PlanMove(mm::unitToAxisUnit<mm::P_pos_t>(delta),
+            mm::unitToAxisUnit<mm::P_speed_t>(feed_rate),
+            mm::unitToAxisUnit<mm::P_speed_t>(end_rate));
+    }
 
     /// @returns rounded current position (rotation) of the Pulley
     /// This exists purely to avoid expensive float (long double) computations of distance traveled by the filament