compiler: Revert -Zregparm handling for extern Rust

compiler/rustc_target/src/callconv/mod.rs

@@ -720,28 +720,6 @@ pub fn adjust_for_foreign_abi<C>(
 
         Ok(())
     }
-
-    pub fn fill_inregs_for_rust_abi<C>(&mut self, cx: &C)
-    where
-        Ty: TyAbiInterface<'a, C> + Copy,
-        C: HasTargetSpec + HasX86AbiOpt,
-    {
-        let spec = cx.target_spec();
-        match &spec.arch[..] {
-            "x86" => {
-                x86::fill_inregs(
-                    cx,
-                    self,
-                    x86::X86Options {
-                        flavor: x86::Flavor::General,
-                        regparm: cx.x86_abi_opt().regparm,
-                    },
-                    true,
-                );
-            }
-            _ => {}
-        }
-    }
 }
 
 impl FromStr for Conv {

compiler/rustc_ty_utils/src/abi.rs

@@ -797,9 +797,6 @@ fn unadjust<'tcx>(arg: &mut ArgAbi<'tcx, Ty<'tcx>>) {
         for (arg_idx, arg) in fn_abi.args.iter_mut().enumerate() {
             fixup(arg, Some(arg_idx));
         }
-        if tcx.sess.target.arch == "x86" {
-            fn_abi.fill_inregs_for_rust_abi(cx);
-        }
     } else {
         fn_abi
             .adjust_for_foreign_abi(cx, abi)

tests/codegen/regparm-inreg-rust-cc.rs

@@ -1,53 +0,0 @@
-// Checks how `regparm` flag works with Rust calling convention with array types.
-// When there is a small array type in signature (casted to combined int type),
-//   inregs will not be set. PassMode::Cast is unsupported.
-// x86 only.
-
-//@ compile-flags: --target i686-unknown-linux-gnu -O -C no-prepopulate-passes
-//@ needs-llvm-components: x86
-
-//@ revisions:regparm0 regparm1 regparm2 regparm3
-//@[regparm0] compile-flags: -Zregparm=0
-//@[regparm1] compile-flags: -Zregparm=1
-//@[regparm2] compile-flags: -Zregparm=2
-//@[regparm3] compile-flags: -Zregparm=3
-
-#![crate_type = "lib"]
-#![no_core]
-#![feature(no_core, lang_items)]
-
-#[lang = "sized"]
-trait Sized {}
-#[lang = "copy"]
-trait Copy {}
-
-pub mod tests {
-    // CHECK: @f1(i16 %0, i32 noundef %_2, i32 noundef %_3)
-    #[no_mangle]
-    pub extern "Rust" fn f1(_: [u8; 2], _: i32, _: i32) {}
-
-    // CHECK: @f2(i24 %0, i32 noundef %_2, i32 noundef %_3)
-    #[no_mangle]
-    pub extern "Rust" fn f2(_: [u8; 3], _: i32, _: i32) {}
-
-    // regparm0: @f3(ptr {{.*}} %_1, i32 noundef %_2, i32 noundef %_3)
-    // regparm1: @f3(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 noundef %_3)
-    // regparm2: @f3(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 inreg noundef %_3)
-    // regparm3: @f3(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 inreg noundef %_3)
-    #[no_mangle]
-    pub extern "Rust" fn f3(_: [u8; 7], _: i32, _: i32) {}
-
-    // regparm0: @f4(ptr {{.*}} %_1, i32 noundef %_2, i32 noundef %_3)
-    // regparm1: @f4(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 noundef %_3)
-    // regparm2: @f4(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 inreg noundef %_3)
-    // regparm3: @f4(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 inreg noundef %_3)
-    #[no_mangle]
-    pub extern "Rust" fn f4(_: [u8; 11], _: i32, _: i32) {}
-
-    // regparm0: @f5(ptr {{.*}} %_1, i32 noundef %_2, i32 noundef %_3)
-    // regparm1: @f5(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 noundef %_3)
-    // regparm2: @f5(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 inreg noundef %_3)
-    // regparm3: @f5(ptr {{.*}} %_1, i32 inreg noundef %_2, i32 inreg noundef %_3)
-    #[no_mangle]
-    pub extern "Rust" fn f5(_: [u8; 33], _: i32, _: i32) {}
-}

tests/codegen/regparm-inreg.rs

@@ -25,13 +25,6 @@ pub mod tests {
     #[no_mangle]
     pub extern "fastcall" fn f1(_: i32, _: i32, _: i32) {}
 
-    // regparm0: @f2(i32 noundef %_1, i32 noundef %_2, i32 noundef %_3)
-    // regparm1: @f2(i32 inreg noundef %_1, i32 noundef %_2, i32 noundef %_3)
-    // regparm2: @f2(i32 inreg noundef %_1, i32 inreg noundef %_2, i32 noundef %_3)
-    // regparm3: @f2(i32 inreg noundef %_1, i32 inreg noundef %_2, i32 inreg noundef %_3)
-    #[no_mangle]
-    pub extern "Rust" fn f2(_: i32, _: i32, _: i32) {}
-
     // regparm0: @f3(i32 noundef %_1, i32 noundef %_2, i32 noundef %_3)
     // regparm1: @f3(i32 inreg noundef %_1, i32 noundef %_2, i32 noundef %_3)
     // regparm2: @f3(i32 inreg noundef %_1, i32 inreg noundef %_2, i32 noundef %_3)