[llvm-bugs] [Bug 49690] New: [RegAlloc: Subreg liveness] Bad machine code: Subrange must not be empty

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49690

            Bug ID: 49690
           Summary: [RegAlloc: Subreg liveness] Bad machine code: Subrange
                    must not be empty
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: paulsson at linux.vnet.ibm.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 24684
  --> https://bugs.llvm.org/attachment.cgi?id=24684&action=edit
reduced testcase

llc -mcpu=arch13 -O3 -disable-machine-dce -disable-cgp -systemz-subreg-liveness
-join-globalcopies=false -verify-misched  tc_crash0_aftercreduce.ll

# Before machine scheduling.
********** INTERVALS **********
R2L [0B,16r:0)[176r,192r:1)  0 at 0B-phi 1 at 176r
R2H [0B,16r:0)[176r,192r:1)  0 at 0B-phi 1 at 176r
%0 [16r,144r:0)[160B,176r:0)  0 at 16r L0000000000000000 EMPTY LFFFFFFFFFFFFFFFF
[16r,144r:0)[160B,176r:0)  0 at 16r weight:0.000000e+00
%3 [48r,64r:0)  0 at 48r weight:0.000000e+00
RegMasks:
********** MACHINEINSTRS **********
# Machine code for function e: NoPHIs, TracksLiveness, TiedOpsRewritten
Function Live Ins: $r2d in %1

0B      bb.0.bb:
          successors: %bb.2(0x80000000), %bb.1(0x00000000); %bb.2(100.00%),
%bb.1(0.00%)
          liveins: $r2d
16B       %0:gr64bit = COPY $r2d
48B       %3:grx32bit = LHIMux 0
64B       CHIMux %3:grx32bit, 0, implicit-def $cc
80B       BRC 14, 6, %bb.2, implicit killed $cc
96B       J %bb.1

112B    bb.1.bb1:
        ; predecessors: %bb.0

144B      STGRL %0:gr64bit, @d :: (store 8 into @d)

160B    bb.2.bb3:
        ; predecessors: %bb.0

176B      $r2d = COPY %0:gr64bit
192B      Return implicit $r2d

# End machine code for function e.

*** Bad machine code: Subrange must not be empty ***
- function:    e
- liverange:   EMPTY
- v. register: %0

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