[x86/Linux] Use GCInfo for funclet unwinding

[parjong]

This commit revises x86/Linux unwinder to use GCInfo(GetPushedArgSize) for funclet unwinding.

This commit includes the following additional changes:

• Enforce fully interruptible codegen for functions with EH funclet
• Enforce full arg info emission even for EBP frames

[parjong]

@dotnet-bot test Ubuntu x64 Formatting please

[parjong]

@dotnet-bot test Ubuntu arm Cross Release Build please

[danmoseley]

@dotnet-bot Test OSX10.12 x64 Checked Build and Test (build break fix)

[janvorli]

A nit, could you please name it hasPartialArgInfo instead (like in "the current frame has partial arg info")?

[janvorli]

@jkotas, @BruceForstall can you please share your opinion on making the funclets fully interruptible and generating full arg info for them? I would like to make sure there are no downsides I don't see.

[jkotas]

The downsides are bigger GC info and lower JIT throughput. Each of these hacks make FEATURE_FIXED_OUT_ARGS more appealing.

[BruceForstall]

Please don't insert the code here; I don't want to dilute or confuse the comment here. Instead, add code below the #endif // _TARGET_X86_ below, e.g.:

#ifdef UNIX_X86_ABI
if (info.compXcptnsCount > 0)
{
assert(!codeGen->isGCTypeFixed());
// Enforce fully interruptible codegen for funclet unwinding
genInterruptible = true;
}
#endif // UNIX_X86_ABI

[BruceForstall]

As a data point, can you compute the increase in GC info size on System.Private.CoreLib.ni.dll? If you can use jit-diff (from jitutils), the jit-diff diff command takes a --gcinfo argument that might help, although I'm not sure if it automatically adds up the size of all GC info and compares it base vs. diff.

[parjong]

@BruceForstall jit-diff is still unavailable on x86/Linux. It seems that jit-diff has a strict dependency on dotnet host which is unavailable, yet:

runtime/corerun jitutils/bin/jit-diff.dll diff
Environment variable JIT_UTILS_ROOT not found - no configuration loaded.

Unhandled Exception: System.InvalidOperationException: Unable to locate dotnet multiplexer
   at Microsoft.DotNet.Cli.Utils.Muxer.get_MuxerPath()
   at Microsoft.DotNet.Cli.Utils.MuxerCommandResolver.Resolve(CommandResolverArguments commandResolverArguments)
   at Microsoft.DotNet.Cli.Utils.CompositeCommandResolver.Resolve(CommandResolverArguments commandResolverArguments)
   at Microsoft.DotNet.Cli.Utils.CommandResolver.TryResolveCommandSpec(ICommandResolverPolicy commandResolverPolicy, String commandName, IEnumerable`1 args, NuGetFramework framework, String configuration, String outputPath, String applicationName)
   at Microsoft.DotNet.Cli.Utils.Command.Create(ICommandResolverPolicy commandResolverPolicy, String commandName, IEnumerable`1 args, NuGetFramework framework, String configuration, String outputPath, String applicationName)
   at ManagedCodeGen.jitdiff.TryCommand(String name, IEnumerable`1 commandArgs, Boolean capture)
   at ManagedCodeGen.jitdiff.Config.SetRID()
   at ManagedCodeGen.jitdiff.Config..ctor(String[] args)
   at ManagedCodeGen.jitdiff.Main(String[] args)
Aborted (core dumped)

[BruceForstall]

@parjong Have you tried jit-diff on linux/x64? You could do Linux/x86 asm diffs there using the altjit.

[parjong]

@BruceForstall I tried, but x86/Linux JIT cannot be loaded from x64/Linux crossgen due to dynamic library issue. x86/Linux JIT is linked to x86/Linux libunwind which does not exist in x64/Linux.

[BruceForstall]

@parjong ok. you could do it from x86 Windows.