Subzero: Improve handling of alloca instructions of constant size.

src/IceTargetLoweringX86Base.h

Index: src/IceTargetLoweringX86Base.h
diff --git a/src/IceTargetLoweringX86Base.h b/src/IceTargetLoweringX86Base.h
index 4ce2ec188408cd259b64eb5cb5d7db1448cddd0c..cdd07a6065d32da2ae55b2df013c6ede549bd84e 100644
--- a/src/IceTargetLoweringX86Base.h
+++ b/src/IceTargetLoweringX86Base.h
@@ -128,7 +128,8 @@ public:
   }
 
   void finishArgumentLowering(Variable *Arg, Variable *FramePtr,
-                              size_t BasicFrameOffset, size_t &InArgsSizeBytes);
+                              size_t BasicFrameOffset, size_t StackAdjBytes,
+                              size_t &InArgsSizeBytes);
   typename Traits::Address stackVarToAsmOperand(const Variable *Var) const;
 
   typename Traits::InstructionSet getInstructionSet() const {
@@ -675,6 +676,7 @@ protected:
   bool IsEbpBasedFrame = false;
   bool NeedsStackAlignment = false;
   size_t SpillAreaSizeBytes = 0;
+  size_t FixedAllocaSizeBytes = 0;
   std::array<llvm::SmallBitVector, IceType_NUM> TypeToRegisterSet;
   std::array<llvm::SmallBitVector, Traits::RegisterSet::Reg_NUM>
       RegisterAliases;