Auto merge of #83666 - Amanieu:instrprof-order, r=tmandry

Run LLVM coverage instrumentation passes before optimization passes

This matches the behavior of Clang and allows us to remove several
hacks which were needed to ensure functions weren't optimized away
before reaching the instrumentation pass.

Fixes #83429

cc `@richkadel`

r? `@tmandry`

compiler/rustc_middle/src/mir/mono.rs

@@ -84,14 +84,7 @@ impl<'tcx> MonoItem<'tcx> {
             .debugging_opts
             .inline_in_all_cgus
             .unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
-            && !tcx.sess.link_dead_code()
-            && !tcx.sess.instrument_coverage();
-        // Disabled for `-Z instrument-coverage` because some LLVM optimizations can sometimes
-        // break coverage results. A test that failed at certain optimization levels is now
-        // validated at that optimization level (via `compile-flags` directive):
-        //   * `src/test/run-make-fulldeps/coverage/closure.rs` broke with `-C opt-level=2`, and
-        //     also required disabling `internalize_symbols` in
-        //     `rustc_mir/monomorphize/partitioning/mod.rs`
+            && !tcx.sess.link_dead_code();
 
         match *self {
             MonoItem::Fn(ref instance) => {