Fixed a regression bug due to direct Staq IR translation

I was making sure that we only handle the case whereby there is only one qreg but didn't handle the case where the buffer name is different from the default "q".

Tested by: running qcor tests.
Signed-off-by: Thien Nguyen <nguyentm@ornl.gov>

quantum/plugins/staq/compiler/staq_compiler.cpp

@@ -250,7 +250,7 @@ std::shared_ptr<IR> StaqCompiler::compile(const std::string &src,
     }
 
     // Direct translation
-    internal_staq::StaqToIr translate(name);
+    internal_staq::StaqToIr translate(name, countQreq.qregs[0]);
     translate.visit(*prog);
     return translate.getIr();
   }

quantum/plugins/staq/utils/staq_visitors.hpp

@@ -167,8 +167,8 @@ public:
 // Staq AST to XACC IR
 class StaqToIr : public staq::ast::Visitor {
 public:
-  StaqToIr(const std::string &in_kernelName)
-      : m_kernelName(in_kernelName), m_provider(xacc::getIRProvider("quantum")) {}
+  StaqToIr(const std::string &in_kernelName, const std::string &in_regName)
+      : m_kernelName(in_kernelName), m_regName(in_regName), m_provider(xacc::getIRProvider("quantum")) {}
   void visit(VarAccess &) override {}
   // Expressions
   void visit(BExpr &) override {}
@@ -233,6 +233,11 @@ public:
   std::shared_ptr<IR> getIr() {
     auto composite =
         xacc::getService<IRProvider>("quantum")->createComposite(m_kernelName);
+    composite->setBufferNames({m_regName});
+    for (auto &gate: m_runtimeInsts) {
+      std::vector regNames(gate->bits().size(), m_regName);
+      gate->setBufferNames(regNames);
+    }
     // Since the instructions were *compiled* by staq (valid AST),
     // hence, we skip all validation.
     composite->addInstructions(std::move(m_runtimeInsts), false);
@@ -245,6 +250,7 @@ private:
   std::vector<InstPtr> m_runtimeInsts;
   std::shared_ptr<IRProvider> m_provider;
   std::string m_kernelName;
+  std::string m_regName;
 };
 
 using namespace xacc::quantum;