[LLVMdev] Assert in live update from MI scheduler.

[Sergei Larin]

Hello everyone,

  I am working on a release based on the branch 3.1 version of code.
Unfortunately it has enough differences that exact rev does not apply.
I am hitting an assert in liveness update with seemingly trivial code
(attached).

/local/mnt/workspace/slarin/tools/llvm-mainline-merged/lib/CodeGen/LiveInter
valAnalysis.cpp:1078: void
llvm::LiveIntervals::HMEditor::moveAllRangesFrom(llvm::MachineInstr*,
llvm::SlotIndex): Assertion `validator.rangesOk() && "moveAllOperandsFrom
broke liveness."' failed.

The code being scheduled (function "push") is trivial:

# Machine code for function push: Post SSA
Function Live Outs: %R0

0B  BB#0: derived from LLVM BB %entry
16B     %vreg9<def> = TFRI_V4 <ga:@xx_stack>; IntRegs:%vreg9
        Successors according to CFG: BB#1

48B BB#1: derived from LLVM BB %for.cond
        Predecessors according to CFG: BB#0 BB#1
80B     %vreg1<def> = COPY %vreg10<kill>; IntRegs:%vreg1,%vreg10
96B     %vreg10<def> = LDriw %vreg9<kill>, 0; mem:LD4[%stack.0.in]
IntRegs:%vreg10,%vreg9
112B    %vreg9<def> = ADD_ri %vreg10, 8; IntRegs:%vreg9,%vreg10
128B    %vreg6<def> = CMPEQri %vreg10, 0; PredRegs:%vreg6 IntRegs:%vreg10
176B    JMP_cNot %vreg6<kill>, <BB#1>, %PC<imp-def>; PredRegs:%vreg6
192B    JMP <BB#2>
        Successors according to CFG: BB#2 BB#1

208B    BB#2: derived from LLVM BB %for.end
        Predecessors according to CFG: BB#1
224B    %vreg7<def> = LDriw %vreg1<kill>, 0; mem:LD4[%first1](tbaa=!"any
pointer") IntRegs:%vreg7,%vreg1
240B    STriw_GP <ga:@yy_instr>, 0, %vreg7<kill>;
mem:ST4[@yy_instr](tbaa=!"any pointer") IntRegs:%vreg7
256B    JMPR %PC<imp-def>, %R31<imp-use>, %R0<imp-use,undef>

Hexagon MI scheduler is working with BB1 and picks this load:

  %vreg10<def> = LDriw %vreg9<kill>, 0; mem:LD4[%stack.0.in]
IntRegs:%vreg10,%vreg9

To be scheduled first (!). Right there after 

7  clang           0x000000000226aece
llvm::LiveIntervals::handleMove(llvm::MachineInstr*) + 378
8  clang           0x0000000001c2574f
llvm::VLIWMachineScheduler::listScheduleTopDown() + 595
9  clang           0x0000000001c24cd5 llvm::VLIWMachineScheduler::schedule()
+ 505

It does not seem to happen on the trunk.

My question is - Does anyone recognizes the issue, and what patch(es) do I
need to address it. Since my release is based on 3.1, I have to cherry pick
them...
Any lead is highly appreciated.

Thanks.

Sergei  










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