From 6c30bf8579f0ea54919eeccff1030f1b3605851a Mon Sep 17 00:00:00 2001
From: Laurence Tratt <laurie@tratt.net>
Date: Fri, 4 Dec 2020 11:41:53 +0000
Subject: [PATCH] Pointer tagging should be OR not left-shift.

---
 ykrt/src/mt.rs | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/ykrt/src/mt.rs b/ykrt/src/mt.rs
index cc1f8ed6d..7a25a5371 100644
--- a/ykrt/src/mt.rs
+++ b/ykrt/src/mt.rs
@@ -10,7 +10,7 @@ use std::{
     },
     thread::{self, JoinHandle},
 };
-use ykcompile::{CompiledTrace, TraceCompiler};
+use ykcompile::TraceCompiler;
 use yktrace::{sir::SIR, start_tracing, tir::TirTrace, ThreadTracer, TracingKind};
 
 pub type HotThreshold = usize;
@@ -296,7 +296,7 @@ impl MTThread {
                     // FIXME: free up the memory when the trace is no longer used.
                     let ptr = Box::into_raw(Box::new(ct)) as usize;
 
-                    let new_pack = PHASE_COMPILED | (ptr << PHASE_NUM_BITS);
+                    let new_pack = ptr | PHASE_COMPILED;
                     loc.pack.store(new_pack, Ordering::Release);
                     // Free the small block of memory we used as a Location ID.
                     unsafe { Box::from_raw(loc_id) };
@@ -304,12 +304,9 @@ impl MTThread {
                     return None;
                 }
                 PHASE_COMPILED => {
-                    let ptr = (lp >> PHASE_NUM_BITS) as *const u8;
-                    let bct = unsafe { Box::from_raw(ptr as *mut CompiledTrace<I>) };
-                    let tptr = bct.ptr();
-                    let func: fn(&mut I) -> bool = unsafe { mem::transmute(tptr) };
-                    mem::forget(bct);
-                    return Some(func);
+                    let p = (lp & !PHASE_TAG) as *const ();
+                    let f = unsafe { mem::transmute::<_, fn(&mut I) -> bool>(p) };
+                    return Some(f);
                 }
                 _ => unreachable!(),
             }