Turn vreg-reuse back on

A tricky side-effect I didn't think about is that
block-local vregs can now look "live" at the end of
their block.  When using names, there are no other uses/defs,
but if we reassign the vreg there can be.

src/analysis/function_analysis.cpp

@@ -159,6 +159,12 @@ 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.
+    if (block->cfg->getVRegInfo().isBlockLocalVReg(vreg))
+        return false;
+
     if (block->successors.size() == 0)
         return false;
 

src/core/cfg.cpp

@@ -2755,7 +2755,6 @@ public:
 
         auto it = sym_vreg_map.find(id);
         if (sym_vreg_map.end() == it) {
-            ASSERT(next_vreg == sym_vreg_map.size(), "%d %d", next_vreg, sym_vreg_map.size());
             sym_vreg_map[id] = next_vreg;
 
             if (!REUSE_VREGS || step == UserVisible || step == CrossBlock) {
@@ -2813,6 +2812,8 @@ void VRegInfo::assignVRegs(CFG* cfg, const ParamNames& param_names, ScopeInfo* s
     assert(hasVRegsAssigned());
 #if REUSE_VREGS
     assert(vreg_sym_map.size() == num_vregs_cross_block);
+#else
+    assert(vreg_sym_map.size() == num_vregs);
 #endif
 }
 

src/core/cfg.h

@@ -135,9 +135,8 @@ public:
     // Not all vregs correspond to a name; many are our compiler-generated variables.
     bool vregHasName(int vreg) const { return vreg < num_vregs_cross_block; }
 
-// XXX temporarily disable vreg reuse, since for the transition we want to make it very
-// easy to convert between vregs and names.
-#define REUSE_VREGS 0
+// Testing flag to turn off the "vreg reuse" optimization.
+#define REUSE_VREGS 1
 
     InternedString getName(int vreg) const {
         assert(hasVRegsAssigned());