From cbf748993f59682f60dfe620eafea24124f737fb Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Thu, 29 Nov 2018 23:05:23 +0100 Subject: Enable -mergefunc-use-aliases If the Rust LLVM fork is used, enable the -mergefunc-use-aliases flag, which will create aliases for merged functions, rather than inserting a call from one to the other. A number of codegen tests needed to be adjusted, because functions that previously fell below the thunk limit are now being merged. Merging is prevented either using -C no-prepopulate-passes, or by making the functions non-identical. I expect that this is going to break something, somewhere, because it isn't able to deal with aliases properly, but we won't find out until we try :) This fixes #52651. --- src/librustc_codegen_llvm/llvm/ffi.rs | 1 + src/librustc_codegen_llvm/llvm_util.rs | 3 +++ 2 files changed, 4 insertions(+) (limited to 'src/librustc_codegen_llvm') diff --git a/src/librustc_codegen_llvm/llvm/ffi.rs b/src/librustc_codegen_llvm/llvm/ffi.rs index f1a966d7654..9eefeca70cf 100644 --- a/src/librustc_codegen_llvm/llvm/ffi.rs +++ b/src/librustc_codegen_llvm/llvm/ffi.rs @@ -1358,6 +1358,7 @@ extern "C" { pub fn LLVMRustDebugMetadataVersion() -> u32; pub fn LLVMRustVersionMajor() -> u32; pub fn LLVMRustVersionMinor() -> u32; + pub fn LLVMRustIsRustLLVM() -> bool; pub fn LLVMRustAddModuleFlag(M: &Module, name: *const c_char, value: u32); diff --git a/src/librustc_codegen_llvm/llvm_util.rs b/src/librustc_codegen_llvm/llvm_util.rs index 267d7e0d54b..fdb6373bea1 100644 --- a/src/librustc_codegen_llvm/llvm_util.rs +++ b/src/librustc_codegen_llvm/llvm_util.rs @@ -70,6 +70,9 @@ unsafe fn configure_llvm(sess: &Session) { if sess.opts.debugging_opts.disable_instrumentation_preinliner { add("-disable-preinline"); } + if llvm::LLVMRustIsRustLLVM() { + add("-mergefunc-use-aliases"); + } for arg in &sess.opts.cg.llvm_args { add(&(*arg)); -- cgit 1.4.1-3-g733a5 From 850d2f1af0224cf1d442a66c33470791a2597888 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Sun, 2 Dec 2018 14:41:39 +0100 Subject: Run name-anon-globals after all other passes name-anon-globals should always be run at the very end of the pass pipeline, as optimization passes (in particular mergefunc) may introduce new anonymous globals. I believe we did not run into this earlier because it requires the rather specific combination of a) mergefunc merging two weak functions b) compilation not using thinlto. --- src/librustc_codegen_llvm/back/write.rs | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'src/librustc_codegen_llvm') diff --git a/src/librustc_codegen_llvm/back/write.rs b/src/librustc_codegen_llvm/back/write.rs index 7945d381760..a7e53faab21 100644 --- a/src/librustc_codegen_llvm/back/write.rs +++ b/src/librustc_codegen_llvm/back/write.rs @@ -371,15 +371,16 @@ pub(crate) unsafe fn optimize(cgcx: &CodegenContext, .unwrap_or(llvm::CodeGenOptLevel::None); let prepare_for_thin_lto = cgcx.lto == Lto::Thin || cgcx.lto == Lto::ThinLocal || (cgcx.lto != Lto::Fat && cgcx.opts.debugging_opts.cross_lang_lto.enabled()); + with_llvm_pmb(llmod, &config, opt_level, prepare_for_thin_lto, &mut |b| { + llvm::LLVMPassManagerBuilderPopulateFunctionPassManager(b, fpm); + llvm::LLVMPassManagerBuilderPopulateModulePassManager(b, mpm); + }); + have_name_anon_globals_pass = have_name_anon_globals_pass || prepare_for_thin_lto; if using_thin_buffers && !prepare_for_thin_lto { assert!(addpass("name-anon-globals")); have_name_anon_globals_pass = true; } - with_llvm_pmb(llmod, &config, opt_level, prepare_for_thin_lto, &mut |b| { - llvm::LLVMPassManagerBuilderPopulateFunctionPassManager(b, fpm); - llvm::LLVMPassManagerBuilderPopulateModulePassManager(b, mpm); - }) } for pass in &config.passes { -- cgit 1.4.1-3-g733a5