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ZJIT: Create perf map files for profilers (#13941)

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This lets us ZJIT compiled functions show up in the profiles of, say,
perf, or samply.

Fix https://github.com/Shopify/ruby/issues/634
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Max Bernstein 2025-07-17 18:36:44 -04:00 • committed by GitHub
parent 86320a5300
commit 30b1368829
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2 changed files with 42 additions and 2 deletions
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38
zjit/src/codegen.rs
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@ -154,6 +154,20 @@ fn gen_iseq_entry_point_body(cb: &mut CodeBlock, iseq: IseqPtr) -> *const u8 {
start_ptr.map(|start_ptr| start_ptr.raw_ptr(cb)).unwrap_or(std::ptr::null())
}
/// Write an entry to the perf map in /tmp
fn register_with_perf(iseq_name: String, start_ptr: usize, code_size: usize) {
use std::io::Write;
let perf_map = format!("/tmp/perf-{}.map", std::process::id());
let Ok(mut file) = std::fs::OpenOptions::new().create(true).append(true).open(&perf_map) else {
debug!("Failed to open perf map file: {perf_map}");
return;
};
let Ok(_) = writeln!(file, "{:#x} {:#x} zjit::{}", start_ptr, code_size, iseq_name) else {
debug!("Failed to write {iseq_name} to perf map file: {perf_map}");
return;
};
}
/// Compile a JIT entry
fn gen_entry(cb: &mut CodeBlock, iseq: IseqPtr, function: &Function, function_ptr: CodePtr, c_stack_bytes: usize) -> Option<CodePtr> {
// Set up registers for CFP, EC, SP, and basic block arguments
@ -172,7 +186,17 @@ fn gen_entry(cb: &mut CodeBlock, iseq: IseqPtr, function: &Function, function_pt
asm.frame_teardown();
asm.cret(C_RET_OPND);
asm.compile(cb).map(|(start_ptr, _)| start_ptr)
let result = asm.compile(cb).map(|(start_ptr, _)| start_ptr);
if let Some(start_addr) = result {
if get_option!(perf) {
let start_ptr = start_addr.raw_ptr(cb) as usize;
let end_ptr = cb.get_write_ptr().raw_ptr(cb) as usize;
let code_size = end_ptr - start_ptr;
let iseq_name = iseq_get_location(iseq, 0);
register_with_perf(format!("entry for {iseq_name}"), start_ptr, code_size);
}
}
result
}
/// Compile an ISEQ into machine code
@ -255,7 +279,17 @@ fn gen_function(cb: &mut CodeBlock, iseq: IseqPtr, function: &Function) -> Optio
}
// Generate code if everything can be compiled
asm.compile(cb).map(|(start_ptr, gc_offsets)| (start_ptr, gc_offsets, jit))
let result = asm.compile(cb).map(|(start_ptr, gc_offsets)| (start_ptr, gc_offsets, jit));
if let Some((start_ptr, _, _)) = result {
if get_option!(perf) {
let start_usize = start_ptr.raw_ptr(cb) as usize;
let end_usize = cb.get_write_ptr().raw_ptr(cb) as usize;
let code_size = end_usize - start_usize;
let iseq_name = iseq_get_location(iseq, 0);
register_with_perf(iseq_name, start_usize, code_size);
}
}
result
}
/// Compile an instruction