[LLVMbugs] [Bug 23988] New: thumbv7 instruction selection failure v2i64 = cttz

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=23988

            Bug ID: 23988
           Summary: thumbv7 instruction selection failure v2i64 = cttz
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: ARM
          Assignee: unassignedbugs at nondot.org
          Reporter: chh at google.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 14532
  --> https://llvm.org/bugs/attachment.cgi?id=14532&action=edit
preprocessed .cpp file and compilation command

Enclosed are script and source to reproduce a crash in NDK clang (*1).  It
crashes upstream clang too (revision 239800).  Looks like cost model has
changed which invalidates the workaround for the last crash: 
https://android-review.googlesource.com/#/c/120011/1/lib/Target/ARM/ARMTargetTransformInfo.cpp
.  Investigating

fatal error: error in backend: Cannot select: 0xe035d80: v2i64 = cttz 0xe035264
[ORD=4] [ID=34]
dbg:/usr/local/google/_blaze_wuu/7e341fa8ce94ae7e022303126d53824a/google3/util/bits/bits.h:297:10
  0xe035264: v2i64 = bitcast 0xe03649c [ORD=3] [ID=28]
dbg:/usr/local/google/_blaze_wuu/7e341fa8ce94ae7e022303126d53824a/google3/util/geometry/s2cellid.h:438:49
    0xe03649c: v2f64,ch = load 0xd66fd20, 0xdfa70ec,
0xe035408<LD16[%lsr.iv2022](align=1)> [ORD=3] [ID=23]
dbg:/usr/local/google/_blaze_wuu/7e341fa8ce94ae7e022303126d53824a/google3/util/geometry/s2cellid.h:438:49
      0xdfa70ec: i32,ch = CopyFromReg 0xd66fd20, 0xdfaac80 [ORD=2] [ID=18]
        0xdfaac80: i32 = Register %vreg7 [ID=1]
      0xe035408: i32 = undef [ID=3]
In function: _ZNK11S2CellUnion16LeafCellsCoveredEv

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