target-feature: enable rust target features implied by target-cpu

Normally LLVM and rustc agree about what features are implied by
target-cpu, but for NVPTX, LLVM considers sm_* and ptx* features to be
exclusive, which makes sense for codegen purposes. But in Rust, we want
to think of them as:

  sm_{sver} means that the target supports the hardware features of sver

  ptx{pver} means the driver supports PTX ISA pver

Intrinsics usually require a minimum sm_{sver} and ptx{pver}.

Prior to this commit, -Ctarget-cpu=sm_70 would activate only sm_70 and
ptx60 (the minimum PTX version that supports sm_70, which maximizes
driver compatibility). With this commit, it also activates all the
implied target features (sm_20, ..., sm_62; ptx32, ..., ptx50).

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/ui/target-feature/implied-features-nvptx.rs b/tests/ui/target-feature/implied-features-nvptx.rs
new file mode 100644
index 00000000000..1550c99f67a
--- /dev/null
+++ b/tests/ui/target-feature/implied-features-nvptx.rs
@@ -0,0 +1,28 @@
+//@ assembly-output: ptx-linker
+//@ compile-flags: --crate-type cdylib -C target-cpu=sm_80 -Z unstable-options -Clinker-flavor=llbc
+//@ only-nvptx64
+//@ build-pass
+#![no_std]
+#![allow(dead_code)]
+
+#[panic_handler]
+pub fn panic(_info: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+// -Ctarget-cpu=sm_80 directly enables sm_80 and ptx70
+#[cfg(not(all(target_feature = "sm_80", target_feature = "ptx70")))]
+compile_error!("direct target features not enabled");
+
+// -Ctarget-cpu=sm_80 implies all earlier sm_* and ptx* features.
+#[cfg(not(all(
+    target_feature = "sm_60",
+    target_feature = "sm_70",
+    target_feature = "ptx50",
+    target_feature = "ptx60",
+)))]
+compile_error!("implied target features not enabled");
+
+// -Ctarget-cpu=sm_80 implies all earlier sm_* and ptx* features.
+#[cfg(target_feature = "ptx71")]
+compile_error!("sm_80 requires only ptx70, but ptx71 enabled");