Auto merge of #86950 - tmiasko:personality, r=nagisa

Use existing declaration of rust_eh_personality

If crate declares `rust_eh_personality`, re-use existing declaration
as otherwise attempts to set function attributes that follow the
declaration will fail (unless it happens to have exactly the same
type signature as the one predefined in the compiler).

Fixes #70117.
Fixes https://github.com/rust-lang/rust/pull/81469#issuecomment-809428126; probably.

3 files changed, 14 insertions, 5 deletions

diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index 2bb0ce68b17..5675a5d9812 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -928,8 +928,12 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         pers_fn: &'ll Value,
         num_clauses: usize,
     ) -> &'ll Value {
+        // Use LLVMSetPersonalityFn to set the personality. It supports arbitrary Consts while,
+        // LLVMBuildLandingPad requires the argument to be a Function (as of LLVM 12). The
+        // personality lives on the parent function anyway.
+        self.set_personality_fn(pers_fn);
         unsafe {
-            llvm::LLVMBuildLandingPad(self.llbuilder, ty, pers_fn, num_clauses as c_uint, UNNAMED)
+            llvm::LLVMBuildLandingPad(self.llbuilder, ty, None, num_clauses as c_uint, UNNAMED)
         }
     }
 
diff --git a/compiler/rustc_codegen_llvm/src/context.rs b/compiler/rustc_codegen_llvm/src/context.rs
index d6a60956555..59259857b4b 100644
--- a/compiler/rustc_codegen_llvm/src/context.rs
+++ b/compiler/rustc_codegen_llvm/src/context.rs
@@ -386,11 +386,16 @@ impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 } else {
                     "rust_eh_personality"
                 };
-                let fty = self.type_variadic_func(&[], self.type_i32());
-                self.declare_cfn(name, llvm::UnnamedAddr::Global, fty)
+                if let Some(llfn) = self.get_declared_value(name) {
+                    llfn
+                } else {
+                    let fty = self.type_variadic_func(&[], self.type_i32());
+                    let llfn = self.declare_cfn(name, llvm::UnnamedAddr::Global, fty);
+                    attributes::apply_target_cpu_attr(self, llfn);
+                    llfn
+                }
             }
         };
-        attributes::apply_target_cpu_attr(self, llfn);
         self.eh_personality.set(Some(llfn));
         llfn
     }
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 2ade66ac41e..68d566cca09 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -1165,7 +1165,7 @@ extern "C" {
     pub fn LLVMBuildLandingPad(
         B: &Builder<'a>,
         Ty: &'a Type,
-        PersFn: &'a Value,
+        PersFn: Option<&'a Value>,
         NumClauses: c_uint,
         Name: *const c_char,
     ) -> &'a Value;