[PATCH] MIR Serialization: Serialize the UsesPhysRegMask from machine register info.

[Alex L]

2015-08-05 14:17 GMT-07:00 Duncan P. N. Exon Smith <dexonsmith at apple.com>:

>
> > On 2015-Jul-30, at 16:47, Alex L <arphaman at gmail.com> wrote:
> >
> > Hi,
> >
> > This patch serializes the UsesPhysRegMask register mask from the machine
> register
> > information class. The mask is serialized as an inverted
> 'calleeSavedRegisters' mask
> > to keep the output minimal. It uses the following syntax:
> >
> > calleeSavedRegisters: [ '%bh', '%bl', '%bp', '%bpl', '%bx', '%ebp',
> '%ebx',
> >                         '%rbp', '%rbx', '%r12', '%r13', '%r14', '%r15',
> >                         '%r12b', '%r13b', '%r14b', '%r15b', '%r12d',
> '%r13d',
> >                         '%r14d', '%r15d', '%r12w', '%r13w', '%r14w',
> '%r15w' ]
> >
> > As you can see, the sub registers are included in this mask as well.
> >
> > This patch also allows the MIR parser to infer this mask from the
> register mask
> > operands if the machine function doesn't specify it.
> >
> > Cheers,
> > Alex
> > <0001-MIR-Serialization-serialize-the-UsesPhysRegMask-from.patch>
>
> > From ca446d1f7a90691ffcc0c1ac16855e5b0eb7a9d0 Mon Sep 17 00:00:00 2001
> > From: Alex Lorenz <arphaman at gmail.com>
> > Date: Thu, 30 Jul 2015 16:37:25 -0700
> > Subject: [PATCH] MIR Serialization: serialize the UsesPhysRegMask from
> >  register info
> >
> > ---
> >  include/llvm/CodeGen/MIRYamlMapping.h              |  2 +
> >  include/llvm/CodeGen/MachineRegisterInfo.h         |  4 +
> >  lib/CodeGen/MIRParser/MIRParser.cpp                | 31 ++++++++
> >  lib/CodeGen/MIRPrinter.cpp                         | 12 +++
> >  .../MIR/X86/used-physical-register-info.mir        | 89
> ++++++++++++++++++++++
> >  5 files changed, 138 insertions(+)
> >  create mode 100644 test/CodeGen/MIR/X86/used-physical-register-info.mir
> >
> > diff --git a/lib/CodeGen/MIRPrinter.cpp b/lib/CodeGen/MIRPrinter.cpp
> > index f34cef7..9ce7e19 100644
> > --- a/lib/CodeGen/MIRPrinter.cpp
> > +++ b/lib/CodeGen/MIRPrinter.cpp
> > @@ -213,6 +213,18 @@ void MIRPrinter::convert(yaml::MachineFunction &MF,
> >        printReg(I->second, LiveIn.VirtualRegister, TRI);
> >      MF.LiveIns.push_back(LiveIn);
> >    }
> > +  // The used physical register mask is printed as an inverted callee
> saved
> > +  // register mask.
> > +  const BitVector &UsedPhysRegMask = RegInfo.getUsedPhysRegsMask();
> > +  if (UsedPhysRegMask.none())
> > +    return;
>
> Will this cause a problem on the parsing side?  In particular, won't the
> reader infer "the default set" here?  To put it another way, how do you
> express in MIR that no registers should be marked callee-saved?
>

So, this none condition is triggered only when the machine function
doesn't have any register mask operands. Because of that, we don't
really want to serialize it as this mask isn't really active in this case.
And the parser will try to infer it when parsing it back in this case,
but I think it's better if it will do that - if the MIR file wasn't modified
the result mask will stay exactly the same as it was before it was
serialized, and otherwise, if the user modified the MIR file and added
some instructions with register mask operands then the parser will
compute the mask correctly.

But I have updated the patch anyway with a related feature - so now the
parser won't infer the mask when you specify an empty array of
callee-saved registers. Although I'm not sure if it's really that useful,
you wouldn't normally want to have an empty array here anyway.


>
> > +  for (unsigned I = 0, E = UsedPhysRegMask.size(); I != E; ++I) {
> > +    if (!UsedPhysRegMask[I]) {
> > +      yaml::FlowStringValue Reg;
> > +      printReg(I, Reg, TRI);
> > +      MF.CalleeSavedRegisters.push_back(Reg);
> > +    }
> > +  }
> >  }
> >
> >  void MIRPrinter::convert(ModuleSlotTracker &MST,
>
>
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