[LLVMbugs] [Bug 14079] New: Assertion in RegisterScavenger

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=14079

             Bug #: 14079
           Summary: Assertion in RegisterScavenger
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: ARM
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: asl at math.spbu.ru
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 9344
  --> http://llvm.org/bugs/attachment.cgi?id=9344
Testcase

Consider the attached testcase. Running llc on yields an (almost) assertion in
RegisterScavenger:

$ llc bugpoint-reduced-simplified.ll 

# In Register Scavenger
# Machine code for function wombat: Post SSA
Function Live Outs: %Q0 %Q1 %Q2 %Q3

BB#0: derived from LLVM BB %bb
    %Q8<def> = VMOVv4i32 0, pred:14, pred:%noreg
    %D18<def> = VMOVv2i32 0, pred:14, pred:%noreg
    %D16<def,tied2>, %D18<def,tied3> = VTRNd32 %D16<tied0>, %D18<kill,tied1>,
pred:14, pred:%noreg, %Q8<imp-use,kill>, %Q8<imp-def,dead>
    %D4<def> = COPY %D17, %Q8<imp-use,kill>, %Q2<imp-def>
    %D3<def> = VDUPLN32d %D18<kill>, 1, pred:14, pred:%noreg, %Q1<imp-def>
    %Q0<def> = IMPLICIT_DEF
    %Q3<def> = IMPLICIT_DEF
    tBX_RET pred:14, pred:%noreg, %Q0<imp-use,kill>, %Q1<imp-use>,
%Q2<imp-use>, %Q3<imp-use,kill>

# End machine code for function wombat.

*** Bad machine code: Using an undefined physical register ***
- function:    wombat
- basic block: BB#0 bb (0x7fc0e182a5c0)
- instruction: %D4<def> = COPY %D17, %Q8<imp-use,kill>, %Q2<imp-def>
- operand 1:   %D17

*** Bad machine code: Using an undefined physical register ***
- function:    wombat
- basic block: BB#0 bb (0x7fc0e182a5c0)
- instruction: %D4<def> = COPY %D17, %Q8<imp-use,kill>, %Q2<imp-def>
- operand 2:   %Q8<imp-use,kill>
LLVM ERROR: Found 2 machine code errors.

And indeed, noone defines D17. It seems this goes from incorrect COPY
elimination. Before RA we have:

16B        %vreg3<def> = VMOVv4i32 0, pred:14, pred:%noreg; QPR:%vreg3
32B        %vreg7<def> = VMOVv2i32 0, pred:14, pred:%noreg; DPR:%vreg7
96B        %vreg3:dsub_0<def,dead,tied2>, %vreg7<def,tied3> = VTRNd32
%vreg3:dsub_0<kill,tied0>, %vreg7<kill,tied1>, pred:14, pred:%noreg; QPR:%vreg3
DPR:%vreg7
112B        %vreg10:dsub_0<def,read-undef> = COPY %vreg3:dsub_1<kill>;
QPR:%vreg10,%vreg3
128B        %vreg13:dsub_1<def,read-undef> = VDUPLN32d %vreg7<kill>, 1,
pred:14, pred:%noreg; QPR:%vreg13 DPR:%vreg7
144B        %Q0<def> = IMPLICIT_DEF
160B        %Q1<def> = COPY %vreg13<kill>; QPR:%vreg13
176B        %Q2<def> = COPY %vreg10<kill>; QPR:%vreg10

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.