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Fix LTO

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This commit is contained in:
Antoni Boucher 2025-01-09 18:41:32 -05:00
parent 3f23706c6c
commit 34ed154343
1 changed files with 51 additions and 3 deletions
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54
src/back/write.rs
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@ -1,6 +1,6 @@
use std::{env, fs};
use gccjit::OutputKind;
use gccjit::{Context, OutputKind};
use rustc_codegen_ssa::back::link::ensure_removed;
use rustc_codegen_ssa::back::write::{BitcodeSection, CodegenContext, EmitObj, ModuleConfig};
use rustc_codegen_ssa::{CompiledModule, ModuleCodegen};
@ -176,10 +176,58 @@ pub(crate) unsafe fn codegen(
context.add_driver_option("-nostdlib");
// NOTE: this doesn't actually generate an executable. With the above flags, it combines the .o files together in another .o.
context.compile_to_file(
// FIXME FIXME: this produces an object file with GIMPLE IR, but it should
// produce an object file with machine code.
//println!("LTO-ed object file: {:?}", obj_out);
/*context.compile_to_file(
OutputKind::Executable,
obj_out.to_str().expect("path to str"),
);
);*/
let path = obj_out.to_str().expect("path to str");
if fat_lto {
let lto_path = format!("{}.lto", path);
// FIXME(antoyo): The LTO frontend generates the following warning:
// ../build_sysroot/sysroot_src/library/core/src/num/dec2flt/lemire.rs:150:15: warning: type of ‘_ZN4core3num7dec2flt5table17POWER_OF_FIVE_12817ha449a68fb31379e4E’ does not match original declaration [-Wlto-type-mismatch]
// 150 | let (lo5, hi5) = POWER_OF_FIVE_128[index];
// | ^
// lto1: note: ‘_ZN4core3num7dec2flt5table17POWER_OF_FIVE_12817ha449a68fb31379e4E’ was previously declared here
//
// This option is to mute it to make the UI tests pass with LTO enabled.
context.add_driver_option("-Wno-lto-type-mismatch");
// NOTE: this doesn't actually generate an executable. With the above
// flags, it combines the .o files together in another .o.
context.compile_to_file(OutputKind::Executable, &lto_path);
let context = Context::default(); // TODO: might need to set some other flags from new_context.
//context.add_driver_option("-v");
//println!("*** Arch: {}", cgcx.target_arch);
if cgcx.target_arch == "x86" || cgcx.target_arch == "x86_64" {
//println!("**** Added -masm=intel");
//context.add_command_line_option("-masm=intel");
// NOTE: it seems we need to use add_driver_option instead of
// add_command_line_option here because we use the LTO frontend via gcc.
context.add_driver_option("-masm=intel");
}
// NOTE: these two options are needed to invoke LTO to produce an object file.
// We need to initiate a second compilation because the arguments "-x lto"
// needs to be at the very beginning.
// TODO TODO: check that LTO still does the optimizations across different
// object files with this change.
// TODO: this should probably be in a condition `if fat_lto`.
context.add_driver_option("-x");
context.add_driver_option("lto");
context.add_driver_option("-fPIC"); // TODO TODO: only add this flag when necessary.
context.add_driver_option(lto_path);
context.compile_to_file(OutputKind::ObjectFile, path);
} else {
// NOTE: this doesn't actually generate an executable. With the above
// flags, it combines the .o files together in another .o.
context.compile_to_file(OutputKind::Executable, path);
}
} else {
context.compile_to_file(
OutputKind::ObjectFile,