Replace the bl! macro with asm_sym

`bl!` is being used to add a leading underscore on Apple targets.
`asm_sym` has been around since 2022 and handles platform-specific
symbol names automatically, so make use of this instead.

I have verified that `armv7s-apple-ios` still builds correctly.

Author: tgross35

compiler-builtins/src/arm.rs

@@ -1,20 +1,12 @@
 #![cfg(not(feature = "no-asm"))]
-#![allow(unused_imports)]
 
-use core::intrinsics;
-
-// Apple symbols have a leading underscore.
-#[cfg(target_vendor = "apple")]
-macro_rules! bl {
-    ($func:literal) => {
-        concat!("bl _", $func)
-    };
-}
-#[cfg(not(target_vendor = "apple"))]
-macro_rules! bl {
-    ($func:literal) => {
-        concat!("bl ", $func)
-    };
+// Interfaces used by naked trampolines. The signatures are not correct, but this does not matter
+// since we implement the calling convention by hand.
+extern "C" {
+    fn __udivmodsi4();
+    fn __udivmoddi4();
+    fn __divmoddi4();
+    fn __aeabi_idiv();
 }
 
 intrinsics! {
@@ -27,10 +19,11 @@ intrinsics! {
             "push {{lr}}",
             "sub sp, sp, #4",
             "mov r2, sp",
-            bl!("__udivmodsi4"),
+            "bl {trampoline}",
             "ldr r1, [sp]",
             "add sp, sp, #4",
             "pop {{pc}}",
+            trampoline = sym crate::arm::__udivmodsi4
         );
     }
 
@@ -41,23 +34,25 @@ intrinsics! {
             "sub sp, sp, #16",
             "add r4, sp, #8",
             "str r4, [sp]",
-            bl!("__udivmoddi4"),
+            "bl {trampoline}",
             "ldr r2, [sp, #8]",
             "ldr r3, [sp, #12]",
             "add sp, sp, #16",
             "pop {{r4, pc}}",
+            trampoline = sym crate::arm::__udivmoddi4
         );
     }
 
     #[unsafe(naked)]
     pub unsafe extern "C" fn __aeabi_idivmod() {
         core::arch::naked_asm!(
             "push {{r0, r1, r4, lr}}",
-            bl!("__aeabi_idiv"),
+            "bl {trampoline}",
             "pop {{r1, r2}}",
             "muls r2, r2, r0",
             "subs r1, r1, r2",
             "pop {{r4, pc}}",
+            trampoline = sym crate::arm::__aeabi_idiv,
         );
     }
 
@@ -68,11 +63,12 @@ intrinsics! {
             "sub sp, sp, #16",
             "add r4, sp, #8",
             "str r4, [sp]",
-            bl!("__divmoddi4"),
+            "bl {trampoline}",
             "ldr r2, [sp, #8]",
             "ldr r3, [sp, #12]",
             "add sp, sp, #16",
             "pop {{r4, pc}}",
+            trampoline = sym crate::arm::__divmoddi4,
         );
     }