Rollup merge of #92877 - Amanieu:remove_llvm_nounwind, r=Mark-Simulacrum

Remove LLVMRustMarkAllFunctionsNounwind

This was originally introduced in #10916 as a way to remove all landing
pads when performing LTO. However this is no longer necessary today
since rustc properly marks all functions and call-sites as nounwind
where appropriate.

In fact this is incorrect in the presence of `extern "C-unwind"` which
must create a landing pad when compiled with `-C panic=abort` so that
foreign exceptions are caught and properly turned into aborts.

2 files changed, 0 insertions, 18 deletions

diff --git a/compiler/rustc_codegen_llvm/src/back/lto.rs b/compiler/rustc_codegen_llvm/src/back/lto.rs
index ddba43cd1f1..6afa649b6de 100644
--- a/compiler/rustc_codegen_llvm/src/back/lto.rs
+++ b/compiler/rustc_codegen_llvm/src/back/lto.rs
@@ -349,13 +349,6 @@ fn fat_lto(
             );
             save_temp_bitcode(cgcx, &module, "lto.after-restriction");
         }
-
-        if cgcx.no_landing_pads {
-            unsafe {
-                llvm::LLVMRustMarkAllFunctionsNounwind(llmod);
-            }
-            save_temp_bitcode(cgcx, &module, "lto.after-nounwind");
-        }
     }
 
     Ok(LtoModuleCodegen::Fat { module: Some(module), _serialized_bitcode: serialized_bitcode })
@@ -770,16 +763,6 @@ pub unsafe fn optimize_thin_module(
             return Err(write::llvm_err(&diag_handler, msg));
         }
 
-        // Like with "fat" LTO, get some better optimizations if landing pads
-        // are disabled by removing all landing pads.
-        if cgcx.no_landing_pads {
-            let _timer = cgcx
-                .prof
-                .generic_activity_with_arg("LLVM_thin_lto_remove_landing_pads", thin_module.name());
-            llvm::LLVMRustMarkAllFunctionsNounwind(llmod);
-            save_temp_bitcode(cgcx, &module, "thin-lto-after-nounwind");
-        }
-
         // Up next comes the per-module local analyses that we do for Thin LTO.
         // Each of these functions is basically copied from the LLVM
         // implementation and then tailored to suit this implementation. Ideally
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index bc8d7b3e9e2..a1c7d2b4f61 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -2320,7 +2320,6 @@ extern "C" {
     pub fn LLVMRustSetNormalizedTarget(M: &Module, triple: *const c_char);
     pub fn LLVMRustAddAlwaysInlinePass(P: &PassManagerBuilder, AddLifetimes: bool);
     pub fn LLVMRustRunRestrictionPass(M: &Module, syms: *const *const c_char, len: size_t);
-    pub fn LLVMRustMarkAllFunctionsNounwind(M: &Module);
 
     pub fn LLVMRustOpenArchive(path: *const c_char) -> Option<&'static mut Archive>;
     pub fn LLVMRustArchiveIteratorNew(AR: &Archive) -> &mut ArchiveIterator<'_>;