Rollup merge of #143893 - ChrisDenton:eh_personality_optional, r=compiler-errors

Don't require `eh_personality` lang item on targets that have a personality

MSVC and wasm have personalities of their own so Rust's personality function is never called. The removed library  comment has some more details.

Author: fmease

compiler/rustc_passes/src/weak_lang_items.rs

@@ -13,6 +13,14 @@ use crate::errors::{
     MissingLangItem, MissingPanicHandler, PanicUnwindWithoutStd, UnknownExternLangItem,
 };
 
+fn has_personality(tcx: TyCtxt<'_>) -> bool {
+    // MSVC and wasm targets (except emscripten) have their own personalities
+    tcx.sess.target.is_like_msvc
+        || (tcx.sess.target.is_like_wasm
+            && (tcx.sess.target.os != "emscripten"
+                || tcx.sess.opts.unstable_opts.emscripten_wasm_eh))
+}
+
 /// Checks the crate for usage of weak lang items, returning a vector of all the
 /// lang items required by this crate, but not defined yet.
 pub(crate) fn check_crate(
@@ -23,7 +31,7 @@ pub(crate) fn check_crate(
     // These are never called by user code, they're generated by the compiler.
     // They will never implicitly be added to the `missing` array unless we do
     // so here.
-    if items.eh_personality().is_none() {
+    if items.eh_personality().is_none() && !has_personality(tcx) {
         items.missing.push(LangItem::EhPersonality);
     }
     if tcx.sess.target.os == "emscripten"

library/std/src/sys/personality/mod.rs

@@ -16,16 +16,6 @@ mod dwarf;
 cfg_if::cfg_if! {
     if #[cfg(target_os = "emscripten")] {
         mod emcc;
-    } else if #[cfg(any(target_env = "msvc", target_family = "wasm"))] {
-        // This is required by the compiler to exist (e.g., it's a lang item),
-        // but it's never actually called by the compiler because
-        // __CxxFrameHandler3 (msvc) / __gxx_wasm_personality_v0 (wasm) is the
-        // personality function that is always used.  Hence this is just an
-        // aborting stub.
-        #[lang = "eh_personality"]
-        fn rust_eh_personality() {
-            core::intrinsics::abort()
-        }
     } else if #[cfg(any(
         all(target_family = "windows", target_env = "gnu"),
         target_os = "psp",
@@ -36,6 +26,9 @@ cfg_if::cfg_if! {
     ))] {
         mod gcc;
     } else {
+        // Targets that have a pre-defined personality:
+        // - msvc
+        // - wasm (except for emscripten)
         // Targets that don't support unwinding.
         // - os=none ("bare metal" targets)
         // - os=uefi