[llvm] r288189 - [LiveRangeEdit] Handle instructions with no defs correctly.

[Hal Finkel via llvm-commits]

----- Original Message -----
> From: "Geoff Berry via llvm-commits" <llvm-commits at lists.llvm.org>
> To: llvm-commits at lists.llvm.org
> Sent: Tuesday, November 29, 2016 1:31:35 PM
> Subject: [llvm] r288189 - [LiveRangeEdit] Handle instructions with no defs correctly.
> 
> Author: gberry
> Date: Tue Nov 29 13:31:35 2016
> New Revision: 288189
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=288189&view=rev
> Log:
> [LiveRangeEdit] Handle instructions with no defs correctly.
> 
> Summary:
> The code in LiveRangeEdit::eliminateDeadDef() that computes isOrigDef
> doesn't handle instructions in which operand 0 is not a def (e.g.
> KILL)
> correctly.  Add a check that operand 0 is a def before doing the rest
> of
> the isOrigDef computation.
> 
> Reviewers: qcolombet, MatzeB, wmi
> 
> Subscribers: mcrosier, llvm-commits
> 
> Differential Revision: https://reviews.llvm.org/D27174
> 
> Modified:
>     llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp?rev=288189&r1=288188&r2=288189&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp (original)
> +++ llvm/trunk/lib/CodeGen/LiveRangeEdit.cpp Tue Nov 29 13:31:35 2016
> @@ -272,7 +272,8 @@ void LiveRangeEdit::eliminateDeadDef(Mac
>    bool ReadsPhysRegs = false;
>    bool isOrigDef = false;
>    unsigned Dest;
> -  if (VRM && MI->getOperand(0).isReg()) {
> +  if (VRM && MI->getOperand(0).isReg() && MI->getOperand(0).isDef())
> {
> +    assert(MI->getDesc().getNumDefs() == 1);

I see in the review thread that the issue of instructions that define multiple operands was discussed with the comment that, "we don't have to worry about multiple definition because isReallyTriviallyReMaterializableGeneric filter out multidef instructions." Could you please add a comment here explaining that, because I don't think it is obvious.

Thanks again,
Hal

>      Dest = MI->getOperand(0).getReg();
>      unsigned Original = VRM->getOriginal(Dest);
>      LiveInterval &OrigLI = LIS.getInterval(Original);
> 
> 
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-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory