Fix some vreg-reuse confusion

src/analysis/function_analysis.cpp

@@ -158,11 +158,10 @@ bool LivenessAnalysis::isLiveAtEnd(int vreg, CFGBlock* block) {
     if (vreg < block->cfg->getVRegInfo().getNumOfUserVisibleVRegs())
         return true;
 
-    // For block-local vregs, this query doesn't really make sense,
-    // since the vreg will be live but that's probably not what we care about.
-    // It's probably safe to return false, but let's just error for now.
+#ifndef NDEBUG
     if (block->cfg->getVRegInfo().isBlockLocalVReg(vreg))
         return false;
+#endif
 
     if (block->successors.size() == 0)
         return false;
@@ -206,6 +205,14 @@ bool LivenessAnalysis::isLiveAtEnd(int vreg, CFGBlock* block) {
         us_liveness.log(_t.end());
     }
 
+    // For block-local vregs, this query doesn't really make sense,
+    // since the vreg will be live but that's probably not what we care about.
+    // It's probably safe to return false, but let's just error for now.
+    if (block->cfg->getVRegInfo().isBlockLocalVReg(vreg)) {
+        ASSERT(!result_cache[vreg][block], "%d in %d", vreg, block->idx);
+        return false;
+    }
+
     return result_cache[vreg][block];
 }
 

src/core/cfg.cpp

@@ -232,6 +232,9 @@ private:
         CFGBlock* exc_dest;
         // variable names to store the exception (type, value, traceback) in
         InternedString exc_type_name, exc_value_name, exc_traceback_name;
+
+        // Similar to did_why: says whether the block might have been jumped-to
+        bool maybe_taken;
     };
 
     // ---------- Member fields ----------
@@ -1576,6 +1579,7 @@ public:
             curblock->connectTo(exc_dest);
 
         ExcBlockInfo& exc_info = exc_handlers.back();
+        exc_info.maybe_taken = true;
 
         curblock = exc_dest;
         // TODO: need to clear some temporaries here
@@ -2341,7 +2345,7 @@ public:
         InternedString exc_type_name = nodeName("type");
         InternedString exc_value_name = nodeName("value");
         InternedString exc_traceback_name = nodeName("traceback");
-        exc_handlers.push_back({ exc_handler_block, exc_type_name, exc_value_name, exc_traceback_name });
+        exc_handlers.push_back({ exc_handler_block, exc_type_name, exc_value_name, exc_traceback_name, false });
 
         for (AST_stmt* subnode : node->body) {
             subnode->accept(this);
@@ -2464,7 +2468,7 @@ public:
         InternedString exc_value_name = nodeName("value");
         InternedString exc_traceback_name = nodeName("traceback");
         InternedString exc_why_name = nodeName("why");
-        exc_handlers.push_back({ exc_handler_block, exc_type_name, exc_value_name, exc_traceback_name });
+        exc_handlers.push_back({ exc_handler_block, exc_type_name, exc_value_name, exc_traceback_name, false });
 
         CFGBlock* finally_block = cfg->addDeferredBlock();
         pushFinallyContinuation(finally_block, exc_why_name);
@@ -2475,6 +2479,7 @@ public:
                 break;
         }
 
+        bool maybe_exception = exc_handlers.back().maybe_taken;
         exc_handlers.pop_back();
 
         int did_why = continuations.back().did_why; // bad to just reach in like this
@@ -2512,16 +2517,18 @@ public:
                 exitFinallyIf(node, Why::BREAK, exc_why_name);
             if (did_why & (1 << Why::CONTINUE))
                 exitFinallyIf(node, Why::CONTINUE, exc_why_name);
-
+            if (maybe_exception) {
                 CFGBlock* reraise = cfg->addDeferredBlock();
                 CFGBlock* noexc = makeFinallyCont(Why::EXCEPTION, makeLoad(exc_why_name, node, true), reraise);
 
                 cfg->placeBlock(reraise);
                 curblock = reraise;
-            pushReraise(getLastLinenoSub(node->finalbody.back()), exc_type_name, exc_value_name, exc_traceback_name);
+                pushReraise(getLastLinenoSub(node->finalbody.back()), exc_type_name, exc_value_name,
+                            exc_traceback_name);
 
                 curblock = noexc;
             }
+        }
 
         return true;
     }
@@ -2585,7 +2592,7 @@ public:
 
         CFGBlock* exc_block = cfg->addDeferredBlock();
         exc_block->info = "with_exc";
-        exc_handlers.push_back({ exc_block, exc_type_name, exc_value_name, exc_traceback_name });
+        exc_handlers.push_back({ exc_block, exc_type_name, exc_value_name, exc_traceback_name, false });
 
         for (int i = 0; i < node->body.size(); i++) {
             node->body[i]->accept(this);