fix broken ContextPromotionPass, had accidentally used vector::resize instead of vector::reserve and fundamentally broke the pass

src/cpu/backend/x64/x64_emitter.cc

@@ -385,8 +385,10 @@ const Xbyak::Operand &X64Emitter::CopyOperand(const Xbyak::Operand &from,
       LOG(FATAL) << "Unsupported copy";
     }
   } else if (to.isMEM() && from.isMEM()) {
-    c_.mov(c_.r8, from);
-    c_.mov(to, c_.r8);
+    const Xbyak::Reg &tmp = GetTmpRegister(nullptr, from.getBit() >> 3);
+    c_.mov(tmp, from);
+    c_.mov(to, tmp);
+    // FIXME could release tmp register now
   } else {
     c_.mov(to, from);
   }

src/cpu/ir/passes/context_promotion_pass.cc

@@ -8,11 +8,17 @@ using namespace dreavm::cpu::ir::passes;
 void ContextPromotionPass::Run(IRBuilder &builder) {
   PROFILER_SCOPE("runtime", "ContextPromotionPass::Run");
 
+  ResetState();
+
   for (auto block : builder.blocks()) {
     ProcessBlock(block);
   }
 }
 
+void ContextPromotionPass::ResetState() {
+  ClearAvailable();
+}
+
 void ContextPromotionPass::ProcessBlock(Block *block) {
   // eliminate redundant loads
   {
@@ -79,14 +85,30 @@ void ContextPromotionPass::ProcessBlock(Block *block) {
   }
 }
 
-void ContextPromotionPass::ClearAvailable() { available_.clear(); }
+void ContextPromotionPass::ClearAvailable() {
+  available_marker_++;
+}
+
+void ContextPromotionPass::ReserveAvailable(int offset) {
+  if (offset >= (int)available_.size()) {
+    available_.resize(offset + 1);
+    available_values_.resize(offset + 1);
+  }
+}
 
 Value *ContextPromotionPass::GetAvailable(int offset) {
-  available_.resize(offset + 1);
-  return available_.at(offset);
+  ReserveAvailable(offset);
+
+  if (available_[offset] < available_marker_) {
+    return nullptr;
+  }
+
+  return available_values_[offset];
 }
 
 void ContextPromotionPass::SetAvailable(int offset, Value *v) {
-  available_.resize(offset + 1);
-  available_.at(offset) = v;
+  ReserveAvailable(offset);
+
+  available_[offset] = available_marker_;
+  available_values_[offset] = v;
 }

src/cpu/ir/passes/context_promotion_pass.h

@@ -14,13 +14,16 @@ class ContextPromotionPass : public Pass {
   void Run(IRBuilder &builder);
 
  private:
+  void ResetState();
   void ProcessBlock(Block *block);
-
   void ClearAvailable();
+  void ReserveAvailable(int offset);
   Value *GetAvailable(int offset);
   void SetAvailable(int offset, Value *v);
 
-  std::vector<Value *> available_;
+  uint64_t available_marker_;
+  std::vector<uint64_t> available_;
+  std::vector<Value *> available_values_;
 };
 }
 }