Dynamically generate new block for assert terminator trans.

This removes the unreachable_block cache, since we no longer utilize it.

Author: Mark-Simulacrum

src/librustc_trans/mir/block.rs

@@ -254,15 +254,6 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
         bcx.llbb()
     }
 
-    pub fn unreachable_block(&mut self) -> BasicBlockRef {
-        self.unreachable_block.unwrap_or_else(|| {
-            let bl = self.new_block("unreachable");
-            bl.unreachable();
-            self.unreachable_block = Some(bl.llbb());
-            bl.llbb()
-        })
-    }
-
     pub fn new_block(&self, name: &str) -> Builder<'a, 'tcx> {
         Builder::new_block(self.ccx, self.llfn, name)
     }

src/librustc_trans/mir/mod.rs

@@ -73,9 +73,6 @@ pub struct MirContext<'a, 'tcx:'a> {
     /// and eagerly on MSVC.
     landing_pads: IndexVec<mir::Block, Option<BasicBlockRef>>,
 
-    /// Cached unreachable block
-    unreachable_block: Option<BasicBlockRef>,
-
     /// The location where each MIR arg/var/tmp/ret is stored. This is
     /// usually an `LvalueRef` representing an alloca, but not always:
     /// sometimes we can skip the alloca and just store the value
@@ -236,7 +233,6 @@ pub fn trans_mir<'a, 'tcx: 'a>(
         ccx: ccx,
         llpersonalityslot: None,
         blocks: block_bcxs,
-        unreachable_block: None,
         cleanup_kinds: cleanup_kinds,
         landing_pads: IndexVec::from_elem(None, mir.basic_blocks()),
         scopes: scopes,

src/librustc_trans/mir/statement.rs

@@ -239,15 +239,19 @@ impl<'a, 'tcx> MirContext<'a, 'tcx> {
 
         // Translate the actual panic invoke/call.
         if let Some(unwind) = cleanup {
-            bcx.invoke(llfn,
-                        &args,
-                        self.unreachable_block(),
-                        self.landing_pad_to(unwind),
-                        cleanup_bundle);
+            let old_bcx = bcx;
+            bcx = old_bcx.build_sibling_block("assert-next");
+            old_bcx.invoke(
+                llfn,
+                &args,
+                bcx.llbb(),
+                self.landing_pad_to(unwind),
+                cleanup_bundle
+            );
         } else {
             bcx.call(llfn, &args, cleanup_bundle);
-            bcx.unreachable();
         }
+        bcx.unreachable();
 
         success_block
     }