more

.gitignore

@@ -1,5 +1,8 @@
 /good
 /bad
+*.ll
+*.s
+a.out
 
 # Added by cargo
 

Cargo.toml

@@ -5,7 +5,7 @@ edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
-[[bin]]
+[lib]
 name = "code"
 path = "./code.rs"
 

check.sh

@@ -1,7 +1,7 @@
 #/usr/bin/env bash
 
-rustc code.rs --crate-name bad -Zmir-enable-passes=-ConstProp -Copt-level=3
+rustc code.rs --crate-name bad -Zmir-enable-passes=-ConstProp -Copt-level=3 --cfg pure_rust
-rustc code.rs --crate-name good -Zmir-enable-passes=+ConstProp -Copt-level=3
+rustc code.rs --crate-name good -Zmir-enable-passes=+ConstProp -Copt-level=3 --cfg pure_rust
 
 bad=$(./bad)
 good=$(./good)

checkllvm.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+
+rustc code.rs --crate-name ll -Zmir-enable-passes=-ConstProp --emit llvm-ir -Cno-prepopulate-passes --crate-type=lib
+
+clang ll.ll helper.c
+
+./a.out

code.rs

@@ -1,9 +1,18 @@
 use std::ptr;
-#[inline(never)]
+
-pub fn print_var(v: u8) {
+extern "C" {
-    println!("{v}");
+    pub fn print_var(v: u8);
 }
-pub unsafe fn fn12_rs() {
+#[cfg(pure_rust)]
+mod impl_ {
+    #[no_mangle]
+    pub extern "C" fn print_var(v: u8) {
+        println!("{v}");
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn fn12_rs() {
     let mut bool_storage: bool = false;
     let mut v9: usize = 0;
 
@@ -12,7 +21,8 @@ pub unsafe fn fn12_rs() {
         let v20_ptr = ptr::addr_of_mut!(v20);
         let mut v12: *mut u8 = core::ptr::addr_of_mut!((*v20_ptr)[v9]);
         v9 = 2_usize; // unused but necessary write
-        loop { // only runs once, but necessary
+        loop {
+            // only runs once, but necessary
             match *v12 {
                 197 => {
                     let mut match_condition: u64 = 0;
@@ -60,7 +70,9 @@ pub unsafe fn fn12_rs() {
         }
     }
 }
-pub fn main() {
+
+#[cfg(pure_rust)]
+fn main() {
     unsafe {
         fn12_rs();
     }

helper.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <stdint.h>
+
+void print_var(uint8_t x) {
+    printf("%d", x);
+}
+
+void fn12_rs();
+
+int main() {
+    fn12_rs();
+}