Improve use of CfgLocalAllocator and introduce containers that use it.

This doesn't make a big difference but does reduce the proportion of time spent
in malloc and free.

BUG=
R=stichnot@chromium.org

Review URL: https://codereview.chromium.org/1349833005 .

src/IceCfgNode.cpp

diff --git a/src/IceCfgNode.cpp b/src/IceCfgNode.cpp
index 31a6e8a..dbbfc18 100644
--- a/src/IceCfgNode.cpp
+++ b/src/IceCfgNode.cpp
@@ -827,7 +827,7 @@
 // Helper functions for emit().
 
 void emitRegisterUsage(Ostream &Str, const Cfg *Func, const CfgNode *Node,
-                       bool IsLiveIn, std::vector<SizeT> &LiveRegCount) {
+                       bool IsLiveIn, CfgVector<SizeT> &LiveRegCount) {
   if (!BuildDefs::dump())
     return;
   Liveness *Liveness = Func->getLiveness();
@@ -840,7 +840,7 @@
     Str << "\t\t\t\t# LiveOut=";
   }
   if (!Live->empty()) {
-    std::vector<Variable *> LiveRegs;
+    CfgVector<Variable *> LiveRegs;
     for (SizeT i = 0; i < Live->size(); ++i) {
       if ((*Live)[i]) {
         Variable *Var = Liveness->getVariable(i, Node);
@@ -869,7 +869,7 @@
 }
 
 void emitLiveRangesEnded(Ostream &Str, const Cfg *Func, const Inst *Instr,
-                         std::vector<SizeT> &LiveRegCount) {
+                         CfgVector<SizeT> &LiveRegCount) {
   if (!BuildDefs::dump())
     return;
   bool First = true;
@@ -935,7 +935,7 @@
   // each register is assigned to. Normally that would be only 0 or 1, but the
   // register allocator's AllowOverlap inference allows it to be greater than 1
   // for short periods.
-  std::vector<SizeT> LiveRegCount(Func->getTarget()->getNumRegisters());
+  CfgVector<SizeT> LiveRegCount(Func->getTarget()->getNumRegisters());
   if (DecorateAsm) {
     constexpr bool IsLiveIn = true;
     emitRegisterUsage(Str, Func, this, IsLiveIn, LiveRegCount);