Subzero: Improve handling of alloca instructions of constant size.

src/IceTargetLowering.h

 //===- subzero/src/IceTargetLowering.h - Lowering interface -----*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 341 matching lines @@
     Context.getLastInserted()->setDestNonKillable();
   }
 
   bool shouldOptimizeMemIntrins();
 
   Cfg *Func;
   GlobalContext *Ctx;
   bool HasComputedFrame = false;
   bool CallsReturnsTwice = false;
   /// StackAdjustment keeps track of the current stack offset from its natural
-  /// location, as arguments are pushed for a function call.
+  /// location, e.g. as arguments are pushed for a function call or as
+  /// fixed-size alloca instructions are executed in the entry block.
   int32_t StackAdjustment = 0;
   SizeT NextLabelNumber = 0;
   SizeT NextJumpTableNumber = 0;
   LoweringContext Context;
 
   // Runtime helper function names
   const static constexpr char *H_bitcast_16xi1_i16 = "__Sz_bitcast_16xi1_i16";
   const static constexpr char *H_bitcast_8xi1_i8 = "__Sz_bitcast_8xi1_i8";
   const static constexpr char *H_bitcast_i16_16xi1 = "__Sz_bitcast_i16_16xi1";
   const static constexpr char *H_bitcast_i8_8xi1 = "__Sz_bitcast_i8_8xi1";
@@ skipping 80 matching lines @@
   virtual void lower() {}
 
 protected:
   explicit TargetHeaderLowering(GlobalContext *Ctx) : Ctx(Ctx) {}
   GlobalContext *Ctx;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERING_H