Remove no-asm gating when there is no alternative implementation

Assembly-related configuration was added in 1621c6d ("Use
`specialized-div-rem` 1.0.0 for division algorithms") to account for
Cranelift not yet supporting assembly. This hasn't been relevant for a
while, so we no longer need to gate `asm!` behind this configuration.
Thus, remove `cfg(not(feature = "no-asm"))` in places where there is no
generic fallback.

There are other cases, however, where setting the `no-asm` configuration
enables testing of generic version of builtins when there are platform-
specific implementations available; these cases are left unchanged. This
could be improved in the future by exposing both versions for testing
rather than using a configuration and running the entire testsuite
twice.

This is the compiler-builtins portion of
rust-lang/rust#144471.

Author: tgross35

builtins-shim/Cargo.toml

@@ -37,8 +37,9 @@ default = ["compiler-builtins"]
 # implementations and also filling in unimplemented intrinsics
 c = ["dep:cc"]
 
-# Workaround for the Cranelift codegen backend. Disables any implementations
-# which use inline assembly and fall back to pure Rust versions (if available).
+# For implementations where there is both a generic version and a platform-
+# specific version, use the generic version. This is meant to enable testing
+# the generic versions on all platforms.
 no-asm = []
 
 # Workaround for codegen backends which haven't yet implemented `f16` and

builtins-test/tests/lse.rs

@@ -1,6 +1,6 @@
 #![feature(decl_macro)] // so we can use pub(super)
 #![feature(macro_metavar_expr_concat)]
-#![cfg(all(target_arch = "aarch64", target_os = "linux", not(feature = "no-asm")))]
+#![cfg(all(target_arch = "aarch64", target_os = "linux"))]
 
 /// Translate a byte size to a Rust type.
 macro int_ty {

compiler-builtins/Cargo.toml

@@ -35,8 +35,9 @@ default = ["compiler-builtins"]
 # implementations and also filling in unimplemented intrinsics
 c = ["dep:cc"]
 
-# Workaround for the Cranelift codegen backend. Disables any implementations
-# which use inline assembly and fall back to pure Rust versions (if available).
+# For implementations where there is both a generic version and a platform-
+# specific version, use the generic version. This is meant to enable testing
+# the generic versions on all platforms.
 no-asm = []
 
 # Workaround for codegen backends which haven't yet implemented `f16` and

compiler-builtins/src/aarch64.rs

@@ -4,7 +4,7 @@ use core::intrinsics;
 
 intrinsics! {
     #[unsafe(naked)]
-    #[cfg(all(target_os = "uefi", not(feature = "no-asm")))]
+    #[cfg(target_os = "uefi")]
     pub unsafe extern "custom" fn __chkstk() {
         core::arch::naked_asm!(
             ".p2align 2",

compiler-builtins/src/arm.rs

@@ -1,5 +1,3 @@
-#![cfg(not(feature = "no-asm"))]
-
 // Interfaces used by naked trampolines.
 // SAFETY: these are defined in compiler-builtins
 unsafe extern "C" {

compiler-builtins/src/hexagon.rs

@@ -1,5 +1,3 @@
-#![cfg(not(feature = "no-asm"))]
-
 use core::arch::global_asm;
 
 global_asm!(include_str!("hexagon/func_macro.s"), options(raw));

compiler-builtins/src/lib.rs

@@ -60,7 +60,7 @@ pub mod arm;
 #[cfg(any(target_arch = "aarch64", target_arch = "arm64ec"))]
 pub mod aarch64;
 
-#[cfg(all(target_arch = "aarch64", target_os = "linux", not(feature = "no-asm"),))]
+#[cfg(all(target_arch = "aarch64", target_os = "linux"))]
 pub mod aarch64_linux;
 
 #[cfg(all(

compiler-builtins/src/probestack.rs

@@ -44,8 +44,6 @@
 #![cfg(not(feature = "mangled-names"))]
 // Windows and Cygwin already has builtins to do this.
 #![cfg(not(any(windows, target_os = "cygwin")))]
-// All these builtins require assembly
-#![cfg(not(feature = "no-asm"))]
 // We only define stack probing for these architectures today.
 #![cfg(any(target_arch = "x86_64", target_arch = "x86"))]
 

compiler-builtins/src/x86.rs

@@ -9,10 +9,7 @@ use core::intrinsics;
 
 intrinsics! {
     #[unsafe(naked)]
-    #[cfg(all(
-        any(all(windows, target_env = "gnu"), target_os = "uefi"),
-        not(feature = "no-asm")
-    ))]
+    #[cfg(any(all(windows, target_env = "gnu"), target_os = "uefi"))]
     pub unsafe extern "custom" fn __chkstk() {
         core::arch::naked_asm!(
             "jmp {}", // Jump to __alloca since fallthrough may be unreliable"
@@ -21,10 +18,7 @@ intrinsics! {
     }
 
     #[unsafe(naked)]
-    #[cfg(all(
-        any(all(windows, target_env = "gnu"), target_os = "uefi"),
-        not(feature = "no-asm")
-    ))]
+    #[cfg(any(all(windows, target_env = "gnu"), target_os = "uefi"))]
     pub unsafe extern "custom" fn _alloca() {
         // __chkstk and _alloca are the same function
         core::arch::naked_asm!(

compiler-builtins/src/x86_64.rs

@@ -9,14 +9,7 @@ use core::intrinsics;
 
 intrinsics! {
     #[unsafe(naked)]
-    #[cfg(all(
-        any(
-            all(windows, target_env = "gnu"),
-            target_os = "cygwin",
-            target_os = "uefi"
-        ),
-        not(feature = "no-asm")
-    ))]
+    #[cfg(any(all(windows, target_env = "gnu"), target_os = "cygwin", target_os = "uefi"))]
     pub unsafe extern "custom" fn ___chkstk_ms() {
         core::arch::naked_asm!(
             "push   %rcx",