Fixes bug on conditional branch where the targets are the same.

src/IceInst.cpp

 //===- subzero/src/IceInst.cpp - High-level instruction implementation ----===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the Inst class, primarily the various
@@ skipping 251 matching lines @@
 }
 
 InstAssign::InstAssign(Cfg *Func, Variable *Dest, Operand *Source)
     : InstHighLevel(Func, Inst::Assign, 1, Dest) {
   addSource(Source);
 }
 
 // If TargetTrue==TargetFalse, we turn it into an unconditional
 // branch.  This ensures that, along with the 'switch' instruction
 // semantics, there is at most one edge from one node to another.
-InstBr::InstBr(Cfg *Func, Operand *Source, CfgNode *TargetTrue,
-               CfgNode *TargetFalse)
-    : InstHighLevel(Func, Inst::Br, 1, nullptr), TargetFalse(TargetFalse),
-      TargetTrue(TargetTrue) {
+InstBr::InstBr(Cfg *Func, Operand *Source, CfgNode *TargetTrue_,
+               CfgNode *TargetFalse_)
+    : InstHighLevel(Func, Inst::Br, 1, nullptr), TargetFalse(TargetFalse_),
+      TargetTrue(TargetTrue_) {

[John, 2015/06/25 21:15:35]

the trailing _ is a great way to differentiate member variables from parameters,
but this is not done (AFAIK) anywhere else.

I would
1) use a different naming convention (ok, this may be hard :)); or
2) change l277 to this->TargetTrue = nullptr

[Jim Stichnoth, 2015/06/25 21:26:29]

I'm very sad that clang didn't give any warnings about this.

I plan to do a CL to add these trailing underscores where appropriate, and also
turn on a warning if it exists.

[Karl, 2015/06/25 22:33:42]

Leaving as is, assuming that Jim will follow through and fix other instances.

   if (TargetTrue == TargetFalse) {
     TargetTrue = nullptr; // turn into unconditional version
   } else {
     addSource(Source);
   }
 }
 
 InstBr::InstBr(Cfg *Func, CfgNode *Target)
     : InstHighLevel(Func, Inst::Br, 0, nullptr), TargetFalse(Target),
       TargetTrue(nullptr) {}
@@ skipping 647 matching lines @@
     // preserve these.
     return true;
   }
   if (!Dest->hasReg() && !SrcVar->hasReg() &&
       Dest->getStackOffset() == SrcVar->getStackOffset())
     return true;
   return false;
 }
 
 } // end of namespace Ice