compiler: Remove TargetOptions::adjust_abi

It has been completely replaced by a declarative, if maybe tedious,
way of translating ABIs.

Author: workingjubilee

compiler/rustc_target/src/callconv/mod.rs

@@ -696,7 +696,6 @@ impl<'a, Ty> FnAbi<'a, Ty> {
             "sparc" => sparc::compute_abi_info(cx, self),
             "sparc64" => sparc64::compute_abi_info(cx, self),
             "nvptx64" => {
-                let abi = cx.target_spec().adjust_abi(abi, self.c_variadic);
                 if abi == ExternAbi::PtxKernel || abi == ExternAbi::GpuKernel {
                     nvptx64::compute_ptx_kernel_abi_info(cx, self)
                 } else {

compiler/rustc_target/src/spec/mod.rs

@@ -2917,54 +2917,6 @@ impl DerefMut for Target {
 }
 
 impl Target {
-    /// Given a function ABI, turn it into the correct ABI for this target.
-    pub fn adjust_abi(&self, abi: ExternAbi, c_variadic: bool) -> ExternAbi {
-        use ExternAbi::*;
-        match abi {
-            // On Windows, `extern "system"` behaves like msvc's `__stdcall`.
-            // `__stdcall` only applies on x86 and on non-variadic functions:
-            // https://learn.microsoft.com/en-us/cpp/cpp/stdcall?view=msvc-170
-            System { unwind } => {
-                if self.is_like_windows && self.arch == "x86" && !c_variadic {
-                    Stdcall { unwind }
-                } else {
-                    C { unwind }
-                }
-            }
-
-            EfiApi => {
-                if self.arch == "arm" {
-                    Aapcs { unwind: false }
-                } else if self.arch == "x86_64" {
-                    Win64 { unwind: false }
-                } else {
-                    C { unwind: false }
-                }
-            }
-
-            // See commentary in `is_abi_supported`.
-            Stdcall { unwind } | Thiscall { unwind } | Fastcall { unwind } => {
-                if self.arch == "x86" { abi } else { C { unwind } }
-            }
-            Vectorcall { unwind } => {
-                if ["x86", "x86_64"].contains(&&*self.arch) {
-                    abi
-                } else {
-                    C { unwind }
-                }
-            }
-
-            // The Windows x64 calling convention we use for `extern "Rust"`
-            // <https://learn.microsoft.com/en-us/cpp/build/x64-software-conventions#register-volatility-and-preservation>
-            // expects the callee to save `xmm6` through `xmm15`, but `PreserveMost`
-            // (that we use by default for `extern "rust-cold"`) doesn't save any of those.
-            // So to avoid bloating callers, just use the Rust convention here.
-            RustCold if self.is_like_windows && self.arch == "x86_64" => Rust,
-
-            abi => abi,
-        }
-    }
-
     pub fn is_abi_supported(&self, abi: ExternAbi) -> bool {
         use ExternAbi::*;
         match abi {