actually encode permissive AbiMapping variants

Author: workingjubilee

compiler/rustc_target/src/spec/abi_map.rs

@@ -63,7 +63,7 @@ impl AbiMap {
 
         let canon_abi = match (extern_abi, arch) {
             // infallible lowerings
-            (ExternAbi::C { .. } | ExternAbi::Cdecl { .. }, _) => CanonAbi::C,
+            (ExternAbi::C { .. }, _) => CanonAbi::C,
             (ExternAbi::Rust | ExternAbi::RustCall, _) => CanonAbi::Rust,
             (ExternAbi::Unadjusted, _) => CanonAbi::C,
 
@@ -94,12 +94,19 @@ impl AbiMap {
                 return AbiMapping::Invalid;
             }
 
+            (ExternAbi::Cdecl { .. }, Arch::X86) => CanonAbi::C,
+            (ExternAbi::Cdecl { .. }, _) => return AbiMapping::Permissive(CanonAbi::C),
+
             (ExternAbi::Fastcall { .. }, Arch::X86) => CanonAbi::X86(X86Call::Fastcall),
-            (ExternAbi::Fastcall { .. }, _) if os == OsKind::Windows => CanonAbi::C,
+            (ExternAbi::Fastcall { .. }, _) if os == OsKind::Windows => {
+                return AbiMapping::Permissive(CanonAbi::C);
+            }
             (ExternAbi::Fastcall { .. }, _) => return AbiMapping::Invalid,
 
             (ExternAbi::Stdcall { .. }, Arch::X86) => CanonAbi::X86(X86Call::Stdcall),
-            (ExternAbi::Stdcall { .. }, _) if os == OsKind::Windows => CanonAbi::C,
+            (ExternAbi::Stdcall { .. }, _) if os == OsKind::Windows => {
+                return AbiMapping::Permissive(CanonAbi::C);
+            }
             (ExternAbi::Stdcall { .. }, _) => return AbiMapping::Invalid,
 
             (ExternAbi::Thiscall { .. }, Arch::X86) => CanonAbi::X86(X86Call::Thiscall),
@@ -108,7 +115,9 @@ impl AbiMap {
             (ExternAbi::Vectorcall { .. }, Arch::X86 | Arch::X86_64) => {
                 CanonAbi::X86(X86Call::Vectorcall)
             }
-            (ExternAbi::Vectorcall { .. }, _) if os == OsKind::Windows => CanonAbi::C,
+            (ExternAbi::Vectorcall { .. }, _) if os == OsKind::Windows => {
+                return AbiMapping::Permissive(CanonAbi::C);
+            }
             (ExternAbi::Vectorcall { .. }, _) => return AbiMapping::Invalid,
 
             (ExternAbi::SysV64 { .. }, Arch::X86_64) => CanonAbi::X86(X86Call::SysV64),