[PATCH] Optimize sext/zext insertion algorithm in back-end

[Jiangning Liu]

Hi majnemer,

All feedbacks are accepted and patch is updated.

Thanks,
-Jiangning

================
Comment at: lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp:68
@@ +67,3 @@
+  ISD::NodeType ExtendKind = ISD::ANY_EXTEND;
+  unsigned int NumOfSigned = 0, NumOfUnsigned = 0;
+  for (const User *U : V->users()) {
----------------
majnemer wrote:
> `int` is redundant.
OK.

================
Comment at: lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp:70
@@ +69,3 @@
+  for (const User *U : V->users()) {
+    if (const CmpInst *CI = dyn_cast<CmpInst>(U)) {
+      NumOfSigned += CI->isSigned();
----------------
majnemer wrote:
> `CmpInst` is redundant with the `dyn_cast`, `auto` would be more concise.
OK.

================
Comment at: lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp:867-868
@@ +866,4 @@
+
+    OpL = GetPromotedInteger(NewLHS);
+    OpR = GetPromotedInteger(NewRHS);
+
----------------
majnemer wrote:
> You'd save some space by declaring `OpL` and `OpR` while defining them.
OK.

http://reviews.llvm.org/D5257