Subzero. Introduces a new LoweringContext::insert() method.

Emitting an instruction in Subzero requires a fair amount of
boilerplated code:

Context.insert(<InstType>::create(Func, <Args>...));

The ordeal is worse if one needs access to the recently create
instructionL

auto *Instr = <InstType>::create(Func, <Args>...);
Context.insert(Instr);
Instr->...

This CL introduces a new LoweringContext::insert() method:

template <<InstType>, <Args>...>
<InstType> *LoweringContext::insert(<Args>...) {
  auto *New = Inst::create(Node.Cfg, <Args>...);
  insert(New);
  return New;
}

This is essentially a syntatic sugar that allows instructions to be
emitted by using

Context.insert<InstType>(<Args>...);

The compiler should be able to inline the calls (and get rid of the
return value) when appropriate.

make bloat reviews a small increase in translator code size

BUG=
R=sehr@chromium.org, stichnot@chromium.org

Review URL: https://codereview.chromium.org/1527143003 .
diff --git a/src/IceTargetLowering.h b/src/IceTargetLowering.h
index 045173b..3d139c0 100644
--- a/src/IceTargetLowering.h
+++ b/src/IceTargetLowering.h
@@ -23,11 +23,14 @@
 #ifndef SUBZERO_SRC_ICETARGETLOWERING_H
 #define SUBZERO_SRC_ICETARGETLOWERING_H
 
+#include "IceCfgNode.h"
 #include "IceDefs.h"
 #include "IceInst.h" // for the names of the Inst subtypes
 #include "IceOperand.h"
 #include "IceTypes.h"
 
+#include <utility>
+
 namespace Ice {
 
 // UnimplementedError is defined as a macro so that we can get actual line
@@ -72,6 +75,11 @@
   InstList::iterator getNext() const { return Next; }
   InstList::iterator getEnd() const { return End; }
   void insert(Inst *Inst);
+  template <typename Inst, typename... Args> Inst *insert(Args &&... A) {
+    auto *New = Inst::create(Node->getCfg(), std::forward<Args>(A)...);
+    insert(New);
+    return New;
+  }
   Inst *getLastInserted() const;
   void advanceCur() { Cur = Next; }
   void advanceNext() { advanceForward(Next); }
@@ -370,9 +378,9 @@
 
   void
   _bundle_lock(InstBundleLock::Option BundleOption = InstBundleLock::Opt_None) {
-    Context.insert(InstBundleLock::create(Func, BundleOption));
+    Context.insert<InstBundleLock>(BundleOption);
   }
-  void _bundle_unlock() { Context.insert(InstBundleUnlock::create(Func)); }
+  void _bundle_unlock() { Context.insert<InstBundleUnlock>(); }
   void _set_dest_redefined() { Context.getLastInserted()->setDestRedefined(); }
 
   bool shouldOptimizeMemIntrins();