[llvm-dev] Check for isConstantPhysReg() in bool LiveRangeCalc::findReachingDefs

[Björn Pettersson A via llvm-dev]

> -----Original Message-----
> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Great
> Indian Bison via llvm-dev
> Sent: den 14 februari 2021 05:53
> To: llvm-dev at lists.llvm.org
> Subject: [llvm-dev] Check for isConstantPhysReg() in bool
> LiveRangeCalc::findReachingDefs
> 
> Hello LLVMDevs,
> Should following code in bool LiveRangeCalc::findReachingDefs() check for
> isConstantPhysReg()?
> Or there is a code which should prevent error below to hit for constant
> physical register?

Not sure, but maybe it is assumed that a constant physical register also
should be defined as being "reserved". And if I recall it correctly
liveness isn't calculated for reserved registers.

> 
>   2     if (Register::isPhysicalRegister(PhysReg) && !MBB-
> >isLiveIn(PhysReg)) {
>   1       MBB->getParent()->verify();
> 225       const TargetRegisterInfo *TRI = MRI->getTargetRegisterInfo();
>   1       errs() << "The register " << printReg(PhysReg, TRI)
>   2              << " needs to be live in to " << printMBBReference(*MBB)
>   3              << ", but is missing from the live-in list.\n";
>   4       report_fatal_error("Invalid global physical register");
>   5     }
> 
> Thanks!
> GI Bison.
> 
> 
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