feat(llvm): add llvm19 support for compute_100+

.github/workflows/ci_linux.yml

@@ -152,11 +152,14 @@ jobs:
               --exclude cust
           '
 
+      # Exclude rustc_codegen_nvvm: `--all-features` enables its `llvm19` feature,
+      # whose build.rs requires an LLVM 19 toolchain not present in the CI image.
       - name: Check documentation
         run: |
           docker exec "$CONTAINER_NAME" bash -lc 'set -euo pipefail
             export RUSTDOCFLAGS=-Dwarnings
-            cargo doc --workspace --all-features --document-private-items --no-deps
+            cargo doc --workspace --all-features --document-private-items --no-deps \
+              --exclude rustc_codegen_nvvm
           '
 
       - name: Stop build container

.github/workflows/ci_windows.yml

@@ -123,12 +123,14 @@ jobs:
             --exclude blastoff --exclude cudnn --exclude cudnn-sys --exclude cust
 
       # Exclude crates that require cuDNN, not available on Windows CI: cudnn, cudnn-sys.
+      # Exclude rustc_codegen_nvvm: `--all-features` enables its `llvm19` feature,
+      # whose build.rs requires an LLVM 19 toolchain not present in the CI image.
       - name: Check documentation
         env:
           RUSTDOCFLAGS: -Dwarnings
         run: |
           cargo doc --workspace --all-features --document-private-items --no-deps `
-            --exclude cudnn --exclude cudnn-sys
+            --exclude cudnn --exclude cudnn-sys --exclude rustc_codegen_nvvm
 
       # Disabled due to dll issues, someone with Windows knowledge needed
       # - name: Compiletest

.gitignore

@@ -2,3 +2,7 @@ book
 /target
 **/.vscode
 .devcontainer
+.codex
+rustc-ice-*.txt
+.nix-driver-libs
+.claude

crates/cuda_builder/Cargo.toml

@@ -16,6 +16,12 @@ default = []
 # HACK(see rust-gpu/spirv-builder): use `dep:` to avoid Cargo auto-creating a feature
 # with the dependency name. Consumers must explicitly opt-in to compiling the backend.
 rustc_codegen_nvvm = ["dep:rustc_codegen_nvvm"]
+# Build the backend against LLVM 19 instead of LLVM 7. Propagates to `nvvm` (which
+# uses it to flip the default `NvvmArch` to `Compute100`) and, when the optional
+# `rustc_codegen_nvvm` dep is also enabled, to `rustc_codegen_nvvm` itself. Even
+# when the optional dep is disabled, the build script's nested `cargo build -p
+# rustc_codegen_nvvm` reads `cfg(feature = "llvm19")` here and forwards it.
+llvm19 = ["nvvm/llvm19", "rustc_codegen_nvvm?/llvm19"]
 
 [dependencies]
 rustc_codegen_nvvm = { version = "0.3", path = "../rustc_codegen_nvvm", optional = true }

crates/cuda_builder/src/lib.rs

@@ -550,13 +550,20 @@ fn build_backend_and_find(filename: &str) -> Option<PathBuf> {
 
     let target_dir = workspace_dir.join("target").join("cuda-builder-codegen");
 
-    let status = Command::new("cargo")
-        .args(["build", "-p", "rustc_codegen_nvvm"])
+    let mut cmd = Command::new("cargo");
+    cmd.args(["build", "-p", "rustc_codegen_nvvm"])
         .arg("--target-dir")
         .arg(&target_dir)
-        .current_dir(&workspace_dir)
-        .status()
-        .ok()?;
+        .current_dir(&workspace_dir);
+
+    // Propagate the `llvm19` cargo feature to the nested backend build. Without this
+    // `rustc_codegen_nvvm`'s build script falls through to the prebuilt LLVM 7
+    // download, which the LLVM 19 codegen path can't link against.
+    if cfg!(feature = "llvm19") {
+        cmd.args(["--features", "llvm19"]);
+    }
+
+    let status = cmd.status().ok()?;
 
     if !status.success() {
         return None;

crates/cust/build.rs

@@ -40,4 +40,12 @@ fn main() {
         println!("cargo::rustc-cfg=cuGraphGetEdges_v2");
         println!("cargo::rustc-cfg=cuCtxCreate_v4");
     }
+
+    // In CUDA 13.2 the `id` field in `CUmemLocation_st` was placed inside an anonymous union.
+    // Bindgen renders this as `__bindgen_anon_1: CUmemLocation_st__bindgen_ty_1` instead of a
+    // direct `id` field. This cfg gates the struct initialization syntax accordingly.
+    println!("cargo::rustc-check-cfg=cfg(cuMemLocation_anon_id)");
+    if driver_version >= 13020 {
+        println!("cargo::rustc-cfg=cuMemLocation_anon_id");
+    }
 }

crates/cust/src/memory/unified.rs

@@ -647,6 +647,9 @@ pub trait MemoryAdvise<T: DeviceCopy>: private::Sealed {
                 #[cfg(cuMemPrefetchAsync_v2)]
                 driver_sys::CUmemLocation {
                     type_: driver_sys::CUmemLocationType::CU_MEM_LOCATION_TYPE_DEVICE,
+                    #[cfg(cuMemLocation_anon_id)]
+                    __bindgen_anon_1: driver_sys::CUmemLocation_st__bindgen_ty_1 { id },
+                    #[cfg(not(cuMemLocation_anon_id))]
                     id,
                 },
                 #[cfg(not(cuMemPrefetchAsync_v2))]
@@ -693,6 +696,9 @@ pub trait MemoryAdvise<T: DeviceCopy>: private::Sealed {
                 #[cfg(cuMemPrefetchAsync_v2)]
                 driver_sys::CUmemLocation {
                     type_: driver_sys::CUmemLocationType::CU_MEM_LOCATION_TYPE_DEVICE,
+                    #[cfg(cuMemLocation_anon_id)]
+                    __bindgen_anon_1: driver_sys::CUmemLocation_st__bindgen_ty_1 { id },
+                    #[cfg(not(cuMemLocation_anon_id))]
                     id,
                 },
                 #[cfg(not(cuMemPrefetchAsync_v2))]
@@ -735,6 +741,9 @@ pub trait MemoryAdvise<T: DeviceCopy>: private::Sealed {
                 #[cfg(cuMemAdvise_v2)]
                 driver_sys::CUmemLocation {
                     type_: driver_sys::CUmemLocationType::CU_MEM_LOCATION_TYPE_DEVICE,
+                    #[cfg(cuMemLocation_anon_id)]
+                    __bindgen_anon_1: driver_sys::CUmemLocation_st__bindgen_ty_1 { id },
+                    #[cfg(not(cuMemLocation_anon_id))]
                     id,
                 },
                 #[cfg(not(cuMemAdvise_v2))]
@@ -777,6 +786,9 @@ pub trait MemoryAdvise<T: DeviceCopy>: private::Sealed {
                 #[cfg(cuMemAdvise_v2)]
                 driver_sys::CUmemLocation {
                     type_: driver_sys::CUmemLocationType::CU_MEM_LOCATION_TYPE_DEVICE,
+                    #[cfg(cuMemLocation_anon_id)]
+                    __bindgen_anon_1: driver_sys::CUmemLocation_st__bindgen_ty_1 { id },
+                    #[cfg(not(cuMemLocation_anon_id))]
                     id,
                 },
                 #[cfg(not(cuMemAdvise_v2))]
@@ -801,6 +813,9 @@ pub trait MemoryAdvise<T: DeviceCopy>: private::Sealed {
                 #[cfg(cuMemAdvise_v2)]
                 driver_sys::CUmemLocation {
                     type_: driver_sys::CUmemLocationType::CU_MEM_LOCATION_TYPE_DEVICE,
+                    #[cfg(cuMemLocation_anon_id)]
+                    __bindgen_anon_1: driver_sys::CUmemLocation_st__bindgen_ty_1 { id },
+                    #[cfg(not(cuMemLocation_anon_id))]
                     id,
                 },
                 #[cfg(not(cuMemAdvise_v2))]

crates/cust_raw/build/cuda_sdk.rs

@@ -215,6 +215,7 @@ impl CudaSdk {
             vec![
                 cuda_root.join("nvvm").join("bin"),
                 cuda_root.join("nvvm").join("lib64"),
+                cuda_root.join("nvvm").join("lib"),
             ]
         };
         let library_dirs = Self::normalize_dirpaths(search_dirs);

crates/cust_raw/build/main.rs

@@ -99,9 +99,12 @@ fn main() {
             println!("cargo::rustc-link-search=native={}", libdir.display());
         }
         println!("cargo::rustc-link-lib=dylib=nvvm");
-        // Handle libdevice support.
-        fs::copy(sdk.libdevice_bitcode_path(), outdir.join("libdevice.bc"))
-            .expect("Cannot copy libdevice bitcode file.");
+        // `fs::copy` preserves source mode. When libdevice.10.bc comes from
+        // the Nix store (0444), re-running this build can't overwrite the
+        // previous copy in OUT_DIR. Drop it first.
+        let dest = outdir.join("libdevice.bc");
+        let _ = fs::remove_file(&dest);
+        fs::copy(sdk.libdevice_bitcode_path(), &dest).expect("Cannot copy libdevice bitcode file.");
     }
 }
 

crates/nvvm/Cargo.toml

@@ -8,6 +8,14 @@ description = "High level bindings to libnvvm"
 repository = "https://github.com/Rust-GPU/rust-cuda"
 readme = "../../README.md"
 
+[features]
+default = []
+# Match the `llvm19` feature on `rustc_codegen_nvvm`. Currently only flips the
+# default `NvvmArch` to the lowest Blackwell capability, since the LLVM 7
+# bitcode dialect can't target `compute_100+` and the LLVM 19 dialect can't
+# target pre-Blackwell archs.
+llvm19 = []
+
 [dependencies]
 cust_raw = { version = "0.11.3", path = "../cust_raw", default-features = false, features = ["nvvm"] }
 strum = { version = "0.27", features = ["derive"] }

crates/nvvm/src/lib.rs

@@ -4,7 +4,6 @@ use std::{
     ffi::{CStr, CString},
     fmt::Display,
     mem::MaybeUninit,
-    ptr::null_mut,
     str::FromStr,
 };
 
@@ -311,12 +310,13 @@ pub enum NvvmArch {
     Compute73,
     /// This default value of 7.5 corresponds to Turing and later devices. We default to this
     /// because it is the minimum supported by CUDA 13.0 while being in the middle of the range
-    /// supported by CUDA 12.x.
+    /// supported by CUDA 12.x. Selected as the default only when the `llvm19` feature is off;
+    /// the LLVM 19 NVVM dialect can't target pre-Blackwell archs.
     // WARNING: If you change the default, consider updating:
     // - The `--target-arch` values used for compiletests in `ci_linux.yml` and
     //   `.github/workflows/ci_{linux,windows}.yml`.
     // - The CUDA versions used in `setup_cuda_environment` in `compiletests`.
-    #[default]
+    #[cfg_attr(not(feature = "llvm19"), default)]
     Compute75,
     Compute80,
     Compute86,
@@ -325,6 +325,12 @@ pub enum NvvmArch {
     Compute89,
     Compute90,
     Compute90a,
+    /// First Blackwell arch and the cutoff for NVVM's modern IR dialect — everything at
+    /// or above this capability uses the LLVM 19-flavored bitcode accepted by CUDA 12.9+
+    /// `libnvvm`. See [`NvvmArch::uses_modern_ir_dialect`]. Selected as the default when
+    /// the `llvm19` feature is enabled, since the LLVM 7 dialect can't target this and
+    /// the LLVM 19 dialect can't target anything below it.
+    #[cfg_attr(feature = "llvm19", default)]
     Compute100,
     Compute100f,
     Compute100a,
@@ -448,6 +454,14 @@ impl NvvmArch {
         self.capability_value() % 10
     }
 
+    /// Whether this target uses NVVM's modern IR dialect rather than the legacy LLVM 7 dialect.
+    ///
+    /// CUDA 13.2 documents the modern dialect as Blackwell-and-later only, which begins at
+    /// `compute_100`.
+    pub fn uses_modern_ir_dialect(&self) -> bool {
+        self.capability_value() >= 100
+    }
+
     /// Get the target feature string (e.g., "compute_50" for `Compute50`, "compute_90a" for
     /// `Compute90a`).
     pub fn target_feature(&self) -> &'static str {
@@ -739,7 +753,24 @@ impl NvvmProgram {
     /// Verify the program without actually compiling it. In the case of invalid IR, you can find
     /// more detailed error info by calling [`compiler_log`](Self::compiler_log).
     pub fn verify(&self) -> Result<(), NvvmError> {
-        unsafe { nvvm_sys::nvvmVerifyProgram(self.raw, 0, null_mut()).to_result() }
+        self.verify_with_options(&[])
+    }
+
+    /// Like [`verify`](Self::verify), but runs the verifier with the same `NvvmOption`s that will
+    /// be passed to [`compile`](Self::compile). Passing the user-selected `-arch=compute_XXX` in
+    /// particular matters for CUDA 12.9+ / LLVM 19 bitcode: without it the verifier can fall back
+    /// to the legacy LLVM 7 parser and reject modern-dialect bitcode that would otherwise compile
+    /// fine.
+    pub fn verify_with_options(&self, options: &[NvvmOption]) -> Result<(), NvvmError> {
+        unsafe {
+            let options = options.iter().map(|x| format!("{x}\0")).collect::<Vec<_>>();
+            let mut options_ptr = options
+                .iter()
+                .map(|x| x.as_ptr().cast())
+                .collect::<Vec<_>>();
+            nvvm_sys::nvvmVerifyProgram(self.raw, options.len() as i32, options_ptr.as_mut_ptr())
+                .to_result()
+        }
     }
 }
 

crates/rustc_codegen_nvvm/Cargo.toml

@@ -14,6 +14,10 @@ readme = "../../README.md"
 [lib]
 crate-type = ["dylib"]
 
+[features]
+default = []
+llvm19 = []
+
 [dependencies]
 nvvm = { version = "0.1", path = "../nvvm" }
 rustc-demangle = "0.1.24"