[llvm-bugs] [Bug 34697] New: Very undeterministic handling of file: different output .s file every time

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=34697

            Bug ID: 34697
           Summary: Very undeterministic handling of file: different
                    output .s file every time
           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 19184
  --> https://bugs.llvm.org/attachment.cgi?id=19184&action=edit
original test case

I noticed that one particular file in SPEC-2006 keeps changing in the .s output
every time as I recompile it (it was the only file to do so).

I tried to track this down with bugpoint and a bisect, but with no luck. The
reduced test case changes output every now and then, but the original input
changes every time. It looks like it could be related to regalloc as
spill/reload instructions show up in the diffs.

bin/clang -cc1 -triple s390x-ibm-linux -S -target-cpu z13 -O3 -vectorize-loops
-vectorize-slp -o out0 -x ir ./Utilities_newsort.bc
bin/clang -cc1 -triple s390x-ibm-linux -S -target-cpu z13 -O3 -vectorize-loops
-vectorize-slp -o out1 -x ir ./Utilities_newsort.bc
diff out0 out1 | less

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