From 5bfa0b106e253e6f8ed93d4c4f44534ccbb13c85 Mon Sep 17 00:00:00 2001
From: Zalathar <Zalathar@users.noreply.github.com>
Date: Sun, 3 Nov 2024 15:15:46 +1100
Subject: [PATCH] Simplify FFI calls for `-Ztime-llvm-passes` and
 `-Zprint-codegen-stats`

---
 compiler/rustc_codegen_llvm/src/lib.rs        | 27 +++----------------
 compiler/rustc_codegen_llvm/src/llvm/ffi.rs   | 10 ++++---
 .../rustc_llvm/llvm-wrapper/RustWrapper.cpp   | 24 +++++------------
 3 files changed, 16 insertions(+), 45 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index b85d28a2f1f..49e616b5371 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -22,7 +22,6 @@
 
 use std::any::Any;
 use std::ffi::CStr;
-use std::io::Write;
 use std::mem::ManuallyDrop;
 
 use back::owned_target_machine::OwnedTargetMachine;
@@ -165,30 +164,12 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     type ThinData = back::lto::ThinData;
     type ThinBuffer = back::lto::ThinBuffer;
     fn print_pass_timings(&self) {
-        unsafe {
-            let mut size = 0;
-            let cstr = llvm::LLVMRustPrintPassTimings(&raw mut size);
-            if cstr.is_null() {
-                println!("failed to get pass timings");
-            } else {
-                let timings = std::slice::from_raw_parts(cstr as *const u8, size);
-                std::io::stdout().write_all(timings).unwrap();
-                libc::free(cstr as *mut _);
-            }
-        }
+        let timings = llvm::build_string(|s| unsafe { llvm::LLVMRustPrintPassTimings(s) }).unwrap();
+        print!("{timings}");
     }
     fn print_statistics(&self) {
-        unsafe {
-            let mut size = 0;
-            let cstr = llvm::LLVMRustPrintStatistics(&raw mut size);
-            if cstr.is_null() {
-                println!("failed to get pass stats");
-            } else {
-                let stats = std::slice::from_raw_parts(cstr as *const u8, size);
-                std::io::stdout().write_all(stats).unwrap();
-                libc::free(cstr as *mut _);
-            }
-        }
+        let stats = llvm::build_string(|s| unsafe { llvm::LLVMRustPrintStatistics(s) }).unwrap();
+        print!("{stats}");
     }
     fn run_link(
         cgcx: &CodegenContext<Self>,
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index d84ae8d8836..2f75457990e 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -1765,11 +1765,13 @@ pub fn LLVMRustBuildAtomicStore<'a>(
     /// Returns a string describing the last error caused by an LLVMRust* call.
     pub fn LLVMRustGetLastError() -> *const c_char;
 
-    /// Print the pass timings since static dtors aren't picking them up.
-    pub fn LLVMRustPrintPassTimings(size: *const size_t) -> *const c_char;
+    /// Prints the timing information collected by `-Ztime-llvm-passes`.
+    #[expect(improper_ctypes)]
+    pub(crate) fn LLVMRustPrintPassTimings(OutStr: &RustString);
 
-    /// Print the statistics since static dtors aren't picking them up.
-    pub fn LLVMRustPrintStatistics(size: *const size_t) -> *const c_char;
+    /// Prints the statistics collected by `-Zprint-codegen-stats`.
+    #[expect(improper_ctypes)]
+    pub(crate) fn LLVMRustPrintStatistics(OutStr: &RustString);
 
     /// Prepares inline assembly.
     pub fn LLVMRustInlineAsm(
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 645b4082be5..a68eed03e61 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -140,26 +140,14 @@ extern "C" void LLVMRustSetNormalizedTarget(LLVMModuleRef M,
   unwrap(M)->setTargetTriple(Triple::normalize(Triple));
 }
 
-extern "C" const char *LLVMRustPrintPassTimings(size_t *Len) {
-  std::string buf;
-  auto SS = raw_string_ostream(buf);
-  TimerGroup::printAll(SS);
-  SS.flush();
-  *Len = buf.length();
-  char *CStr = (char *)malloc(*Len);
-  memcpy(CStr, buf.c_str(), *Len);
-  return CStr;
+extern "C" void LLVMRustPrintPassTimings(RustStringRef OutBuf) {
+  auto OS = RawRustStringOstream(OutBuf);
+  TimerGroup::printAll(OS);
 }
 
-extern "C" const char *LLVMRustPrintStatistics(size_t *Len) {
-  std::string buf;
-  auto SS = raw_string_ostream(buf);
-  llvm::PrintStatistics(SS);
-  SS.flush();
-  *Len = buf.length();
-  char *CStr = (char *)malloc(*Len);
-  memcpy(CStr, buf.c_str(), *Len);
-  return CStr;
+extern "C" void LLVMRustPrintStatistics(RustStringRef OutBuf) {
+  auto OS = RawRustStringOstream(OutBuf);
+  llvm::PrintStatistics(OS);
 }
 
 extern "C" LLVMValueRef LLVMRustGetNamedValue(LLVMModuleRef M, const char *Name,