[llvm-bugs] [Bug 26080] New: Incorrect code gen with fast-isel

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https://llvm.org/bugs/show_bug.cgi?id=26080

            Bug ID: 26080
           Summary: Incorrect code gen with fast-isel
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: PowerPC
          Assignee: unassignedbugs at nondot.org
          Reporter: kbarton at ca.ibm.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 15593
  --> https://llvm.org/bugs/attachment.cgi?id=15593&action=edit
Test case

The attached test case compiles incorrectly at -O0 or with -fast-isel on
ppc64le (P8). 

Steps to reproduce the problem:
Good:
  csmith  llc -O1 wrong1.bc
  csmith  gcc -o wrong1.good wrong1.s
  ./wrong1.good
checksum = DA24AA98

Bad (-O0):
 llc -O0 wrong1.bc
 gcc -o wrong1.bad wrong1.s
 ./wrong1.bad
checksum = D1427FE6

Bad (-O1 -fast-isel):
 llc -O1 -fast-isel wrong1.bc
 gcc -o wrong1.bad wrong1.s
 ./wrong1.bad
checksum = D1427FE6

The good result is reproduced with different opt levels, and with GCC as well.

I have tried to reduce the test with bugpoint, but it was unable to reduce it.

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