[llvm-commits] GC patches again

[Chris Lattner]

BTW, thank you for splitting up this patch!  It makes it much easier  
to review.

> //===-- gc-3-collector.patch (+531) ---------------------------===//
>
>   include/llvm/CodeGen/Collector.h (+134)
>   lib/CodeGen/Collector.cpp (+359)
>   lib/CodeGen/README.txt (+38)
>
> Collector is the base class for garbage collector code generators.
> This version enhances the previous patch to add root initialization
> as discussed here:

+#ifndef LLVM_CODEGEN_GC_H
+#define LLVM_CODEGEN_GC_H

Should probably be LLVM_CODEGEN_COLLECTOR_H

+
+#include "llvm/CodeGen/CollectorMetadata.h"
+#include <ostream>

plz use <iosfwd> instead of <ostream> or neither if you don't need them.

+namespace llvm {
+
+  class AsmPrinter;
+  class FunctionPassManager;
+  class Pass;
+  class PassManager;
+  class TargetAsmInfo;

You can probably remove some of these.

In Collector.cpp, it looks like you have several redundant #include's.

Otherwise, looks great, plz commit.

> //===-- gc-4-integration.patch (+116 -17) ---------------------===//
>
> In this patch, Collector winds its tendrils throughout the compiler.
> Overhead should be minimal when disabled.
>
> I would particularly appreciate any feedback on this interface.
> The primary item of concern to me is that I exposed the desired
> collector to the compiler using a global. I have not decided on a
> better approach. In the meantime, it works and is simple.

I agree, this is not the right way to go.  There are two problems:

1. introducing global data means that two instances of the codegen  
can't be made at the same time.  This is not acceptable.  Fixing this  
should be relatively straight forward: hang any mutable data off  
MachineFunction or MachineModuleInfo as appropriate, and any  
immutable target info off TargetMachine.

2. Adding a -gc option to llc isn't what we really want.  Ideally,  
the code generator would generate gc info for a function iff there is  
a gcroot in it.  This would allow the codegen to emit GC code code  
that obviously uses it.  Is there any case where the codegen has to  
do something for a function with no gcroots (or declared safepoints  
etc) in it?

-Chris