diff options
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/back/write.rs | 2 | ||||
| -rw-r--r-- | compiler/rustc_codegen_llvm/src/llvm/ffi.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_interface/src/tests.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp | 2 | ||||
| -rw-r--r-- | compiler/rustc_session/src/options.rs | 2 | ||||
| -rw-r--r-- | src/doc/unstable-book/src/compiler-flags/no-unique-section-names.md | 9 |
6 files changed, 17 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs index 380dfd38723..82c3c2006eb 100644 --- a/compiler/rustc_codegen_llvm/src/back/write.rs +++ b/compiler/rustc_codegen_llvm/src/back/write.rs @@ -161,6 +161,7 @@ pub fn target_machine_factory( let ffunction_sections = sess.opts.debugging_opts.function_sections.unwrap_or(sess.target.function_sections); let fdata_sections = ffunction_sections; + let funique_section_names = !sess.opts.debugging_opts.no_unique_section_names; let code_model = to_llvm_code_model(sess.code_model()); @@ -205,6 +206,7 @@ pub fn target_machine_factory( use_softfp, ffunction_sections, fdata_sections, + funique_section_names, trap_unreachable, singlethread, asm_comments, diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs index 45fb638e3b4..d57573558da 100644 --- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs +++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs @@ -2187,6 +2187,7 @@ extern "C" { UseSoftFP: bool, FunctionSections: bool, DataSections: bool, + UniqueSectionNames: bool, TrapUnreachable: bool, Singlethread: bool, AsmComments: bool, diff --git a/compiler/rustc_interface/src/tests.rs b/compiler/rustc_interface/src/tests.rs index dab4d485e2d..2d3cb52f5fd 100644 --- a/compiler/rustc_interface/src/tests.rs +++ b/compiler/rustc_interface/src/tests.rs @@ -744,6 +744,7 @@ fn test_debugging_options_tracking_hash() { tracked!(new_llvm_pass_manager, Some(true)); tracked!(no_generate_arange_section, true); tracked!(no_link, true); + tracked!(no_unique_section_names, true); tracked!(no_profiler_runtime, true); tracked!(osx_rpath_install_name, true); tracked!(panic_abort_tests, true); diff --git a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp index d6dc54c8d0a..32b866e81b1 100644 --- a/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp +++ b/compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp @@ -462,6 +462,7 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine( LLVMRustCodeGenOptLevel RustOptLevel, bool UseSoftFloat, bool FunctionSections, bool DataSections, + bool UniqueSectionNames, bool TrapUnreachable, bool Singlethread, bool AsmComments, @@ -491,6 +492,7 @@ extern "C" LLVMTargetMachineRef LLVMRustCreateTargetMachine( } Options.DataSections = DataSections; Options.FunctionSections = FunctionSections; + Options.UniqueSectionNames = UniqueSectionNames; Options.MCOptions.AsmVerbose = AsmComments; Options.MCOptions.PreserveAsmComments = AsmComments; Options.MCOptions.ABIName = ABIStr; diff --git a/compiler/rustc_session/src/options.rs b/compiler/rustc_session/src/options.rs index 782055b9a77..3ff91c0553a 100644 --- a/compiler/rustc_session/src/options.rs +++ b/compiler/rustc_session/src/options.rs @@ -1214,6 +1214,8 @@ options! { "compile without linking"), no_parallel_llvm: bool = (false, parse_no_flag, [UNTRACKED], "run LLVM in non-parallel mode (while keeping codegen-units and ThinLTO)"), + no_unique_section_names: bool = (false, parse_bool, [TRACKED], + "do not use unique names for text and data sections when -Z function-sections is used"), no_profiler_runtime: bool = (false, parse_no_flag, [TRACKED], "prevent automatic injection of the profiler_builtins crate"), normalize_docs: bool = (false, parse_bool, [TRACKED], diff --git a/src/doc/unstable-book/src/compiler-flags/no-unique-section-names.md b/src/doc/unstable-book/src/compiler-flags/no-unique-section-names.md new file mode 100644 index 00000000000..5c1c7cda701 --- /dev/null +++ b/src/doc/unstable-book/src/compiler-flags/no-unique-section-names.md @@ -0,0 +1,9 @@ +# `no-unique-section-names` + +------------------------ + +This flag currently applies only to ELF-based targets using the LLVM codegen backend. It prevents the generation of unique ELF section names for each separate code and data item when `-Z function-sections` is also in use, which is the default for most targets. This option can reduce the size of object files, and depending on the linker, the final ELF binary as well. + +For example, a function `func` will by default generate a code section called `.text.func`. Normally this is fine because the linker will merge all those `.text.*` sections into a single one in the binary. However, starting with [LLVM 12](https://github.com/llvm/llvm-project/commit/ee5d1a04), the backend will also generate unique section names for exception handling, so you would see a section name of `.gcc_except_table.func` in the object file and potentially in the final ELF binary, which could add significant bloat to programs that contain many functions. + +This flag instructs LLVM to use the same `.text` and `.gcc_except_table` section name for each function, and it is analogous to Clang's `-fno-unique-section-names` option. |