[llvm-bugs] [Bug 43319] New: [IndVarSimplify, ScalarEvolution] Compilation hang

via llvm-bugs llvm-bugs at lists.llvm.org
Sun Sep 15 02:10:12 PDT 2019


            Bug ID: 43319
           Summary: [IndVarSimplify, ScalarEvolution]  Compilation hang
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: paulsson at linux.vnet.ibm.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 22498
  --> https://bugs.llvm.org/attachment.cgi?id=22498&action=edit
unreduced test case

This compilation takes a second at -O1, but has been running for a week at -O3. 

It seems that IndVarSimplify calls getBackedgeTakenCount() on an inner loop
with ~30 exiting blocks, which seems to never return.

opt -mtriple=s390x-linux-gnu -mcpu=arch13 -O3 -o out.opt.ll test10872.bc

original command:

clang -cc1 -triple s390x-ibm-linux -S -save-temps=cwd -disable-free
-main-file-name test10872.c -mrelocation-model static -mthread-model posix
-mframe-pointer=none -fmath-errno -masm-verbose -mconstructor-aliases
-fuse-init-array -target-cpu arch13 -dwarf-column-info -debugger-tuning=gdb -O3
 -ferror-limit 19 -fmessage-length 0 -fno-signed-char -fobjc-runtime=gcc
-fdiagnostics-show-option -fcolor-diagnostics -vectorize-loops -vectorize-slp
-faddrsig -o test10872.s -x ir test10872.bc

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