Second attempt at fixing LTO tests

FIXME: we now have fat LTO objects even when only bitcode is requested.

Author: antoyo

Diff for: Readme.md

@@ -121,8 +121,7 @@ If you compiled cg_gccjit in debug mode (aka you didn't pass `--release` to `./y
 
 ### LTO
 
-To use LTO, you need to set the variable `FAT_LTO=1` and `EMBED_LTO_BITCODE=1` in addition to setting `lto = "fat"` in the `Cargo.toml`.
-Don't set `FAT_LTO` when compiling the sysroot, though: only set `EMBED_LTO_BITCODE=1`.
+To use LTO, you need to set the variable `EMBED_LTO_BITCODE=1` in addition to setting `lto = "fat"` in the `Cargo.toml`.
 
 Failing to set `EMBED_LTO_BITCODE` will give you the following error:
 

Diff for: build_system/src/config.rs

@@ -387,12 +387,6 @@ impl ConfigInfo {
             rustflags.push("-Csymbol-mangling-version=v0".to_string());
         }
 
-        // Since we don't support ThinLTO, disable LTO completely when not trying to do LTO.
-        // TODO(antoyo): remove when we can handle ThinLTO.
-        // TODO: remove:
-        /*if !env.contains_key(&"FAT_LTO".to_string()) {
-            rustflags.push("-Clto=off".to_string());
-        }*/
         // FIXME(antoyo): remove once the atomic shim is gone
         if os_name == "Darwin" {
             rustflags.extend_from_slice(&[

Diff for: src/back/lto.rs

@@ -489,7 +489,6 @@ fn thin_lto(
                 //let path = module_buffer.0.to_str().expect("path");
                 //let my_path = PathBuf::from(path);
                 //let exists = my_path.exists();
-                //println!("Path: {:?}: {}", path, exists);
                 /*module.module_llvm.should_combine_object_files = true;
                 module
                 .module_llvm
@@ -626,11 +625,6 @@ pub unsafe fn optimize_thin_module(
             match *module {
                 SerializedModule::Local(ref module_buffer) => {
                     let path = module_buffer.0.to_str().expect("path");
-
-                    //let my_path = PathBuf::from(path);
-                    //let exists = my_path.exists();
-                    //println!("Path2: {:?}: {}", path, exists);
-
                     context.add_driver_option(path);
                     should_combine_object_files = true;
                     /*module.module_llvm.should_combine_object_files = true;

Diff for: src/back/write.rs

@@ -57,6 +57,8 @@ pub(crate) unsafe fn codegen(
                     .generic_activity_with_arg("GCC_module_codegen_emit_bitcode", &*module.name);
                 context.add_command_line_option("-flto=auto");
                 context.add_command_line_option("-flto-partition=one");
+                // TODO: remove since we don't want fat objects when it is for Bitcode only.
+                context.add_command_line_option("-ffat-lto-objects");
                 context
                     .compile_to_file(OutputKind::ObjectFile, bc_out.to_str().expect("path to str"));
             }
@@ -135,7 +137,6 @@ pub(crate) unsafe fn codegen(
                         obj_out.to_str().expect("path to str"),
                     );
                 } else {
-                    //println!("Combining to object file");
                     context.compile_to_file(
                         OutputKind::ObjectFile,
                         obj_out.to_str().expect("path to str"),

Diff for: tests/failing-ui-tests.txt

@@ -94,3 +94,4 @@ tests/ui/consts/const-eval/parse_ints.rs
 tests/ui/simd/intrinsic/generic-arithmetic-pass.rs
 tests/ui/backtrace/backtrace.rs
 tests/ui/lifetimes/tail-expr-lock-poisoning.rs
+tests/ui/runtime/rt-explody-panic-payloads.rs