avr-hal-generic: remove rustc version check

The build.rs logic is only used to detect a relatively old compiler
version (Feb 2022). Since a nightly build is required to target AVR it's
unlikely anyone is benefiting from this check.  By removing it we reduce
dependencies and implementation complexity.

Author: tones111

avr-hal-generic/Cargo.toml

@@ -17,7 +17,6 @@ features = ["docsrs"]
 docsrs = ["avr-device/docsrs"]
 
 [dependencies]
-cfg-if = "1"
 nb = "1.1.0"
 ufmt = "0.2.0"
 paste = "1.0.0"
@@ -31,6 +30,3 @@ unwrap-infallible = "0.1.5"
 version = "0.2.3"
 package = "embedded-hal"
 features = ["unproven"]
-
-[build-dependencies]
-rustversion = "1.0"

avr-hal-generic/build.rs

@@ -4,7 +4,7 @@ use core::marker;
 use embedded_hal::delay::DelayNs;
 use embedded_hal_v0::blocking::delay as delay_v0;
 
-#[cfg(all(target_arch = "avr", avr_hal_asm_macro))]
+#[cfg(target_arch = "avr")]
 use core::arch::asm;
 
 /// A busy-loop delay implementation
@@ -44,38 +44,24 @@ impl<SPEED> Delay<SPEED> {
 
 // based on https://github.com/arduino/ArduinoCore-avr/blob/master/cores/arduino/wiring.c
 
-cfg_if::cfg_if! {
-    if #[cfg(all(target_arch = "avr", avr_hal_asm_macro))] {
-        #[allow(unused_assignments)]
-        fn busy_loop(mut c: u16) {
-            unsafe {
-                asm!(
-                    "1:",
-                    "sbiw {c}, 1",
-                    "brne 1b",
-                    c = inout(reg_iw) c,
-                );
-            }
-        }
-    } else if #[cfg(target_arch = "avr")] {
-        #[allow(unused_assignments)]
-        fn busy_loop(mut c: u16) {
-            unsafe {
-                llvm_asm!("1: sbiw $0,1\n\tbrne 1b"
-                     : "=w"(c)
-                     : "0"(c)
-                     :
-                     : "volatile"
-                 );
-            }
-        }
-    } else {
-        fn busy_loop(_c: u16) {
-            unimplemented!("Implementation is only available for avr targets!")
-        }
+#[cfg(target_arch = "avr")]
+#[allow(unused_assignments)]
+fn busy_loop(mut c: u16) {
+    unsafe {
+        asm!(
+            "1:",
+            "sbiw {c}, 1",
+            "brne 1b",
+            c = inout(reg_iw) c,
+        );
     }
 }
 
+#[cfg(not(target_arch = "avr"))]
+fn busy_loop(_c: u16) {
+    unimplemented!("Implementation is only available for avr targets!")
+}
+
 // Clock-Specific Delay Implementations ----------------------------------- {{{
 impl delay_v0::DelayUs<u16> for Delay<crate::clock::MHz24> {
     fn delay_us(&mut self, mut us: u16) {
@@ -106,16 +92,11 @@ impl delay_v0::DelayUs<u16> for Delay<crate::clock::MHz20> {
 
         // for a one-microsecond delay, simply return.  the overhead
         // of the function call takes 18 (20) cycles, which is 1us
-        #[cfg(all(target_arch = "avr", avr_hal_asm_macro))]
+        #[cfg(target_arch = "avr")]
         unsafe {
             asm!("nop", "nop", "nop", "nop");
         }
 
-        #[cfg(all(target_arch = "avr", not(avr_hal_asm_macro)))]
-        unsafe {
-            llvm_asm!("nop\nnop\nnop\nnop" :::: "volatile");
-        }
-
         if us <= 1 {
             return;
         } // = 3 cycles, (4 when true)

avr-hal-generic/src/delay.rs

@@ -1,6 +1,5 @@
 #![no_std]
-#![cfg_attr(avr_hal_asm_macro, feature(asm_experimental_arch))]
-#![cfg_attr(not(avr_hal_asm_macro), feature(llvm_asm))]
+#![feature(asm_experimental_arch)]
 
 pub use embedded_hal as hal;
 pub use embedded_hal_v0 as hal_v0;