Make `-Zfixed-x18` into a target modifier
As part of #136966, the `-Zfixed-x18` flag should be turned into a target modifier. This is a blocker to stabilization of the flag. The flag was originally added in #124655 and the MCP for its addition is [MCP#748](https://github.com/rust-lang/compiler-team/issues/748).
On some aarch64 targets, the x18 register is used as a temporary caller-saved register by default. When the `-Zfixed-x18` flag is passed, this is turned off so that the compiler doesn't use the x18 register. This allows end-users to use the x18 register for other purposes. For example, by accessing it with inline asm you can use the register as a very efficient thread-local variable. Another common use-case is to store the stack pointer needed by the shadow-call-stack sanitizer. There are also some aarch64 targets where not using x18 is the default – in those cases the flag is a no-op.
Note that this flag does not *on its own* cause an ABI mismatch. What actually causes an ABI mismatch is when you have different compilation units that *disagree* on what it should be used for. But having a CU that uses it and another CU that doesn't normally isn't enough to trigger an ABI problem. However, we still consider the flag to be a target modifier in all cases, since it is assumed that you are passing the flag because you intend to assign some other meaning to the register. Rejecting all flag mismatches even if not all are unsound is consistent with [RFC#3716](https://rust-lang.github.io/rfcs/3716-target-modifiers.html). See the headings "not all mismatches are unsound" and "cases that are not caught" for additional discussion of this.
On aarch64 targets where `-Zfixed-x18` is not a no-op, it is an error to pass `-Zsanitizer=shadow-call-stack` without also passing `-Zfixed-x18`.
implement `PanicTracker` to track `t` panics
Trying to understand panics triggered by `t` macro is very exhausting (especially on CI failures) because it doesn't provide any information about where the macro was originally invoked. This change adds that missing information when an inner call inside the `t` macro panics.
Resolves#137557
`fn check_opaque_type_parameter_valid` defer error
Will be used in #139587 to silence opaque type errors if there are other borrowck failures. I think it can be merged separately.
r? `@compiler-errors`
Removing rustc_type_ir in the rustc_infer codebase
cc #138449
This is a second refactoring of rustc_type_ir to use rustc_middle instead, this time that's for rustc_infer
bypass linker configuration and cross target check on `x check`
I was going to handle this using the untracked env approach, but I realized it somehow doesn't regress https://github.com/rust-lang/rust/issues/130108 anymore...
Anyway, if it works, it works. 😄 No need to dig deeper but my guess is we moved some cache-invalidating env from these functions to others.
Fixes https://github.com/rust-lang/rust/issues/133840
try-job: aarch64-apple
mir-opt: execute MatchBranchSimplification after GVN
This can provide more opportunities for MatchBranchSimplification.
Currently, rustc does not optimize the following code into a single statement at mir-opt, and this PR fixes the first case.
```rust
pub fn match1(c: bool, v1: i32, v2: i32) -> i32 {
if c { v1 - v2 } else { v1 - v2 }
}
pub fn match2(c: bool, v1: i32) -> i32 {
if c { v1 - 1 } else { v1 - 1 }
}
```
https://rust.godbolt.org/z/Y8xPMjrfM
r? mir-opt
