Rollup merge of rust-lang#140395 - RalfJung:target-feature-tests, r=petrochenkov

organize and extend forbidden target feature tests

In particular this adds some loongarch tests for rust-lang#135015, Cc `@heiher`

Seems like the tests change so much git does not detect the renames; a commit-by-commit review should help.

try-job: `x86_64-gnu-llvm-20-*`

Author: matthiaskrgr

tests/ui/target-feature/abi-incompatible-target-feature-attribute.riscv.stderr

@@ -0,0 +1,8 @@
+error: target feature `d` cannot be enabled with `#[target_feature]`: this feature is incompatible with the target ABI
+  --> $DIR/abi-incompatible-target-feature-attribute.rs:15:90
+   |
+LL | #[cfg_attr(x86, target_feature(enable = "soft-float"))] #[cfg_attr(riscv, target_feature(enable = "d"))]
+   |                                                                                          ^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/target-feature/abi-incompatible-target-feature-attribute.rs

@@ -0,0 +1,17 @@
+//! Ensure ABI-incompatible features cannot be enabled via `#[target_feature]`.
+// ignore-tidy-linelength
+//@ compile-flags: --crate-type=lib
+//@ revisions: x86 riscv
+//@[x86] compile-flags: --target=x86_64-unknown-linux-gnu
+//@[x86] needs-llvm-components: x86
+//@[riscv] compile-flags: --target=riscv32e-unknown-none-elf
+//@[riscv] needs-llvm-components: riscv
+#![feature(no_core, lang_items, riscv_target_feature, x87_target_feature)]
+#![no_core]
+
+#[lang = "sized"]
+pub trait Sized {}
+
+#[cfg_attr(x86, target_feature(enable = "soft-float"))] #[cfg_attr(riscv, target_feature(enable = "d"))]
+//~^ERROR: cannot be enabled with
+pub unsafe fn my_fun() {}

tests/ui/target-feature/abi-incompatible-target-feature-attribute.x86.stderr

@@ -0,0 +1,8 @@
+error: target feature `soft-float` cannot be enabled with `#[target_feature]`: this feature is incompatible with the target ABI
+  --> $DIR/abi-incompatible-target-feature-attribute.rs:15:32
+   |
+LL | #[cfg_attr(x86, target_feature(enable = "soft-float"))] #[cfg_attr(riscv, target_feature(enable = "d"))]
+   |                                ^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/target-feature/abi-incompatible-target-feature-flag-enable.riscv.stderr

@@ -0,0 +1,19 @@
+warning: target feature `d` must be disabled to ensure that the ABI of the current target can be implemented correctly
+   |
+   = note: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #116344 <https://github.com/rust-lang/rust/issues/116344>
+
+warning: unstable feature specified for `-Ctarget-feature`: `d`
+   |
+   = note: this feature is not stably supported; its behavior can change in the future
+
+warning: unstable feature specified for `-Ctarget-feature`: `f`
+   |
+   = note: this feature is not stably supported; its behavior can change in the future
+
+warning: unstable feature specified for `-Ctarget-feature`: `zicsr`
+   |
+   = note: this feature is not stably supported; its behavior can change in the future
+
+warning: 4 warnings emitted
+

tests/ui/target-feature/abi-incompatible-target-feature-flag-enable.rs

@@ -0,0 +1,22 @@
+//! Ensure ABI-incompatible features cannot be enabled via `-Ctarget-feature`.
+// These are just warnings for now.
+//@ check-pass
+//@ compile-flags: --crate-type=lib
+//@ revisions: x86 riscv
+//@[x86] compile-flags: --target=x86_64-unknown-linux-gnu -Ctarget-feature=+soft-float
+//@[x86] needs-llvm-components: x86
+//@[riscv] compile-flags: --target=riscv32e-unknown-none-elf -Ctarget-feature=+d
+//@[riscv] needs-llvm-components: riscv
+
+#![feature(no_core, lang_items, riscv_target_feature)]
+#![no_core]
+
+#[lang = "sized"]
+pub trait Sized {}
+#[lang = "freeze"]
+pub trait Freeze {}
+
+//~? WARN must be disabled to ensure that the ABI of the current target can be implemented correctly
+//~? WARN unstable feature specified for `-Ctarget-feature`
+//[riscv]~? WARN unstable feature specified for `-Ctarget-feature`
+//[riscv]~? WARN unstable feature specified for `-Ctarget-feature`

tests/ui/target-feature/forbidden-hardfloat-target-feature-flag.stderr renamed to tests/ui/target-feature/abi-incompatible-target-feature-flag-enable.x86.stderr

@@ -1,3 +1,6 @@
+//! `x87` is a required target feature on some x86 targets, but not on this one as this one
+//! uses soft-floats. So ensure disabling the target feature here (which is a NOP) does
+//! not trigger a warning.
 //@ compile-flags: --target=x86_64-unknown-none --crate-type=lib
 //@ needs-llvm-components: x86
 //@ compile-flags: -Ctarget-feature=-x87

tests/ui/target-feature/allowed-softfloat-target-feature-flag-disable.rs renamed to tests/ui/target-feature/abi-irrelevant-target-feature-flag-disable.rs

@@ -1,3 +1,5 @@
+//! Enabling a target feature that is anyway required changes nothing, so this is allowed
+//! for `#[target_feature]`.
 //@ compile-flags: --target=x86_64-unknown-none --crate-type=lib
 //@ needs-llvm-components: x86
 //@ build-pass