Rollup merge of #138872 - a4lg:riscv-fix-incompatible-abi-zfinx, r=workingjubilee

rustc_target: RISC-V `Zfinx` is incompatible with `{ILP32,LP64}[FD]` ABIs

Because RISC-V Calling Conventions note that:

> This means code targeting the `Zfinx` extension always uses the ILP32,  ILP32E or LP64 integer calling-convention only ABIs as there is no dedicated hardware floating-point register file.

`{ILP32,LP64}[FD]` ABIs with hardware floating-point calling conventions are incompatible with the `Zfinx` extension.

This commit adds `"zfinx"` to the incompatible feature list to those ABIs and tests whether trying to add `"zdinx"` (that is analogous to `"zfinx"` but in double-precision) on a LP64D ABI configuration results in an error (it also tests extension implication; `Zdinx` requires `Zfinx` extension).

Links: RISC-V psABI specification version 1.0
<https://github.com/riscv-non-isa/riscv-elf-psabi-doc/blob/v1.0/riscv-cc.adoc#named-abis>
<https://github.com/riscv-non-isa/riscv-elf-psabi-doc/releases/tag/v1.0>

Author: Zalathar

compiler/rustc_target/src/target_features.rs

@@ -966,12 +966,12 @@ impl Target {
                 // about what the intended ABI is.
                 match &*self.llvm_abiname {
                     "ilp32d" | "lp64d" => {
-                        // Requires d (which implies f), incompatible with e.
-                        FeatureConstraints { required: &["d"], incompatible: &["e"] }
+                        // Requires d (which implies f), incompatible with e and zfinx.
+                        FeatureConstraints { required: &["d"], incompatible: &["e", "zfinx"] }
                     }
                     "ilp32f" | "lp64f" => {
-                        // Requires f, incompatible with e.
-                        FeatureConstraints { required: &["f"], incompatible: &["e"] }
+                        // Requires f, incompatible with e and zfinx.
+                        FeatureConstraints { required: &["f"], incompatible: &["e", "zfinx"] }
                     }
                     "ilp32" | "lp64" => {
                         // Requires nothing, incompatible with e.

tests/ui/target-feature/forbidden-hardfloat-target-feature-attribute.rs renamed to tests/ui/target-feature/forbidden-hardfloat-target-feature-attribute-e-d.rs

@@ -1,5 +1,5 @@
 error: target feature `d` cannot be enabled with `#[target_feature]`: this feature is incompatible with the target ABI
-  --> $DIR/forbidden-hardfloat-target-feature-attribute.rs:10:18
+  --> $DIR/forbidden-hardfloat-target-feature-attribute-e-d.rs:10:18
    |
 LL | #[target_feature(enable = "d")]
    |                  ^^^^^^^^^^^^

tests/ui/target-feature/forbidden-hardfloat-target-feature-attribute.stderr renamed to tests/ui/target-feature/forbidden-hardfloat-target-feature-attribute-e-d.stderr

@@ -0,0 +1,12 @@
+//! Ensure ABI-incompatible features cannot be enabled via `#[target_feature]`.
+//@ compile-flags: --target=riscv64gc-unknown-linux-gnu --crate-type=lib
+//@ needs-llvm-components: riscv
+#![feature(no_core, lang_items, riscv_target_feature)]
+#![no_core]
+
+#[lang = "sized"]
+pub trait Sized {}
+
+#[target_feature(enable = "zdinx")]
+//~^ERROR: cannot be enabled with
+pub unsafe fn my_fun() {}

tests/ui/target-feature/forbidden-hardfloat-target-feature-attribute-f-zfinx.rs

@@ -0,0 +1,8 @@
+error: target feature `zfinx` cannot be enabled with `#[target_feature]`: this feature is incompatible with the target ABI
+  --> $DIR/forbidden-hardfloat-target-feature-attribute-f-zfinx.rs:10:18
+   |
+LL | #[target_feature(enable = "zdinx")]
+   |                  ^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+