[PATCH] Implement the x86 lowering for inalloca

[Dan Gohman]

  > Index: include/llvm/Target/TargetCallingConv.h
  > ===================================================================
  > --- include/llvm/Target/TargetCallingConv.h
  > +++ include/llvm/Target/TargetCallingConv.h
  > @@ -42,6 +42,8 @@
  >      static const uint64_t ByValAlignOffs = 7;
  >      static const uint64_t Split          = 1ULL<<11;
  >      static const uint64_t SplitOffs      = 11;
  > +    static const uint64_t InAlloca       = 1ULL<<12; ///< Passed in alloca
  > +    static const uint64_t InAllocaOffs   = 12;

  Change the comment to say "Passed with inalloca" since inalloca means a bunch of things beyond just using an alloca.

  > Index: include/llvm/Target/TargetLowering.h
  > ===================================================================
  > --- include/llvm/Target/TargetLowering.h
  > +++ include/llvm/Target/TargetLowering.h
  > @@ -24,6 +24,7 @@
  >  #define LLVM_TARGET_TARGETLOWERING_H
  >
  >  #include "llvm/ADT/DenseMap.h"
  > +#include "llvm/CodeGen/CallingConvLower.h"

  Is this #include needed? It looks like it's for CallLoweringInfo and CCState, which could
  be forward-declared.

  > Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  > ===================================================================
  > --- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  > +++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
  [...]
  > +  // Dynamically allocate space for the stack frame.
  > +  // TODO: Can we support args aligned to greater than the stack alignment?
  > +  unsigned Align = 0;

  The (unchecked) assumption that default stack alignment is enough seems dangerous. How hard would it be to implement this? Is it just a matter of computing the greatest alignment from the arguments, or does it require additional codegen support?

  [...]
  > +      if (Args[i].isInAlloca) {
  > +        Flags.setByVal();  // TODO: Remove when isInAlloca() works.

  Does isInAlloca not work yet?

  > Index: lib/Target/X86/X86ISelLowering.cpp
  > ===================================================================
  > --- lib/Target/X86/X86ISelLowering.cpp
  > +++ lib/Target/X86/X86ISelLowering.cpp
  > @@ -2501,6 +2501,21 @@
  >    return Chain;
  >  }
  >
  > +void X86TargetLowering::AnalyzeCallArgs(TargetLowering::CallLoweringInfo &CLI,
  > +                                        CCState &CCInfo) const {
  > +  SelectionDAG &DAG                     = CLI.DAG;
  > +  SmallVectorImpl<ISD::OutputArg> &Outs = CLI.Outs;
  > +  CallingConv::ID CallConv              = CLI.CallConv;
  > +  bool isVarArg                         = CLI.IsVarArg;
  > +  MachineFunction &MF = DAG.getMachineFunction();

  DAG, isVarArg, and MF are unused here.

http://llvm-reviews.chandlerc.com/D2450

BRANCH
  inalloca-codegen

ARCANIST PROJECT
  llvm