CGCall: Factor out the logic mapping call arguments to LLVM IR arguments.

Summary:
This refactoring introduces ClangToLLVMArgMapping class, which
encapsulates the information about the order in which function arguments listed
in CGFunctionInfo should be passed to actual LLVM IR function, such as:
1) positions of sret, if there is any
2) position of inalloca argument, if there is any
3) position of helper padding argument for each call argument
4) positions of regular argument (there can be many if it's expanded).
Simplify several related methods (ConstructAttributeList, EmitFunctionProlog
and EmitCall): now they don't have to maintain iterators over the list
of LLVM IR function arguments, dealing with all the sret/inalloca/this complexities,
and just use expected positions of LLVM IR arguments stored in ClangToLLVMArgMapping.

This may increase the running time of EmitFunctionProlog, as we have to traverse
expandable arguments twice, but in further refactoring we will be able
to speed up EmitCall by passing already calculated CallArgsToIRArgsMapping to
ConstructAttributeList, thus avoiding traversing expandable argument there.

No functionality change.

Test Plan: regression test suite

Reviewers: majnemer, rnk

Reviewed By: rnk

Subscribers: cfe-commits, rjmccall, timurrrr

Differential Revision: http://reviews.llvm.org/D4938

llvm-svn: 216251

1 files changed, 9 insertions, 12 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 37b7c2e..04294ec 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2598,18 +2598,15 @@ private:
   /// from function arguments into \arg Dst. See ABIArgInfo::Expand.
   ///
   /// \param AI - The first function argument of the expansion.
-  /// \return The argument following the last expanded function
-  /// argument.
-  llvm::Function::arg_iterator
-  ExpandTypeFromArgs(QualType Ty, LValue Dst,
-                     llvm::Function::arg_iterator AI);
-
-  /// ExpandTypeToArgs - Expand an RValue \arg Src, with the LLVM type for \arg
-  /// Ty, into individual arguments on the provided vector \arg Args. See
-  /// ABIArgInfo::Expand.
-  void ExpandTypeToArgs(QualType Ty, RValue Src,
-                        SmallVectorImpl<llvm::Value *> &Args,
-                        llvm::FunctionType *IRFuncTy);
+  void ExpandTypeFromArgs(QualType Ty, LValue Dst,
+                          SmallVectorImpl<llvm::Argument *>::iterator &AI);
+
+  /// ExpandTypeToArgs - Expand an RValue \arg RV, with the LLVM type for \arg
+  /// Ty, into individual arguments on the provided vector \arg IRCallArgs,
+  /// starting at index \arg IRCallArgPos. See ABIArgInfo::Expand.
+  void ExpandTypeToArgs(QualType Ty, RValue RV, llvm::FunctionType *IRFuncTy,
+                        SmallVectorImpl<llvm::Value *> &IRCallArgs,
+                        unsigned &IRCallArgPos);
 
   llvm::Value* EmitAsmInput(const TargetInfo::ConstraintInfo &Info,
                             const Expr *InputExpr, std::string &ConstraintStr);