Nvptx: Use llbc as default linker

Author: Kjetil Kjeka

compiler/rustc_target/src/spec/mod.rs

@@ -2793,8 +2793,8 @@ impl Target {
         );
         check_eq!(
             self.arch == Arch::Nvptx64,
-            matches!(self.linker_flavor, LinkerFlavor::Ptx),
-            "`linker_flavor` must be `ptc` if and only if `arch` is `nvptx64`"
+            matches!(self.linker_flavor, LinkerFlavor::Llbc),
+            "`linker_flavor` must be `llbc` if `arch` is `nvptx64`"
         );
 
         for args in [

compiler/rustc_target/src/spec/targets/nvptx64_nvidia_cuda.rs

@@ -19,9 +19,7 @@ pub(crate) fn target() -> Target {
         options: TargetOptions {
             os: "cuda".into(),
             vendor: "nvidia".into(),
-            linker_flavor: LinkerFlavor::Ptx,
-            // The linker can be installed from `crates.io`.
-            linker: Some("rust-ptx-linker".into()),
+            linker_flavor: LinkerFlavor::Llbc,
 
             // With `ptx-linker` approach, it can be later overridden via link flags.
             cpu: "sm_30".into(),

src/doc/rustc/src/platform-support/nvptx64-nvidia-cuda.md

@@ -12,7 +12,7 @@ platform.
 
 ## Requirements
 
-This target is `no_std` and will typically be built with crate-type `cdylib` and `-C linker-flavor=llbc`, which generates PTX.
+This target is `no_std` using `llvm-bitcode-linker` by default. For PTX output, build with crate-type `cdylib`.
 The necessary components for this workflow are:
 
 - `rustup toolchain add nightly`
@@ -38,7 +38,7 @@ While the compiler accepts `#[target_feature(enable = "ptx80", enable = "sm_89")
 A `no_std` crate containing one or more functions with `extern "ptx-kernel"` can be compiled to PTX using a command like the following.
 
 ```console
-$ RUSTFLAGS='-Ctarget-cpu=sm_89' cargo +nightly rustc --target=nvptx64-nvidia-cuda -Zbuild-std=core --crate-type=cdylib -- -Clinker-flavor=llbc -Zunstable-options
+$ RUSTFLAGS='-Ctarget-cpu=sm_89' cargo +nightly rustc --target=nvptx64-nvidia-cuda -Zbuild-std=core --crate-type=cdylib
 ```
 
 Intrinsics in `core::arch::nvptx` may use `#[cfg(target_feature = "...")]`, thus it's necessary to use `-Zbuild-std=core` with appropriate `RUSTFLAGS`. The following components are needed for this workflow:

tests/assembly-llvm/nvptx-arch-default.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: ptx-linker
-//@ compile-flags: --crate-type cdylib -Z unstable-options -Clinker-flavor=llbc
+//@ compile-flags: --crate-type cdylib
 //@ only-nvptx64
 
 #![no_std]

tests/assembly-llvm/nvptx-arch-target-cpu.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: ptx-linker
-//@ compile-flags: --crate-type cdylib -C target-cpu=sm_50 -Z unstable-options -Clinker-flavor=llbc
+//@ compile-flags: --crate-type cdylib -C target-cpu=sm_50
 //@ only-nvptx64
 
 #![no_std]

tests/assembly-llvm/nvptx-c-abi-arg-v7.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: ptx-linker
-//@ compile-flags: --crate-type cdylib -C target-cpu=sm_86 -Z unstable-options -Clinker-flavor=llbc
+//@ compile-flags: --crate-type cdylib -C target-cpu=sm_86
 //@ only-nvptx64
 
 // The PTX ABI stability is tied to major versions of the PTX ISA

tests/assembly-llvm/nvptx-c-abi-ret-v7.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: ptx-linker
-//@ compile-flags: --crate-type cdylib -C target-cpu=sm_86 -Z unstable-options -Clinker-flavor=llbc
+//@ compile-flags: --crate-type cdylib -C target-cpu=sm_86
 //@ only-nvptx64
 
 // The PTX ABI stability is tied to major versions of the PTX ISA

tests/assembly-llvm/nvptx-kernel-abi/nvptx-kernel-args-abi-v7.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: ptx-linker
-//@ compile-flags: --crate-type cdylib -C target-cpu=sm_86 -Z unstable-options -Clinker-flavor=llbc
+//@ compile-flags: --crate-type cdylib -C target-cpu=sm_86
 //@ only-nvptx64
 
 // The following ABI tests are made with nvcc 11.6 does.

tests/assembly-llvm/nvptx-safe-naming.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: ptx-linker
-//@ compile-flags: --crate-type cdylib -Z unstable-options -Clinker-flavor=llbc
+//@ compile-flags: --crate-type cdylib
 //@ only-nvptx64
 //@ revisions: LLVM20 LLVM21
 //@ [LLVM21] min-llvm-version: 21