[llvm-bugs] [Bug 45479] New: clang constant-folds away runtime test of stack alignment

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45479

            Bug ID: 45479
           Summary: clang constant-folds away runtime test of stack
                    alignment
           Product: libraries
           Version: trunk
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: AArch64
          Assignee: unassignedbugs at nondot.org
          Reporter: roland at hack.frob.com
                CC: arnaud.degrandmaison at arm.com,
                    llvm-bugs at lists.llvm.org, smithp352 at googlemail.com,
                    Ties.Stuij at arm.com

Created attachment 23333
  --> https://bugs.llvm.org/attachment.cgi?id=23333&action=edit
reproducer (preprocessed C++)

With attached reproducer, clang generates code that takes the __zx_panic path
unconditionally. The asm should force it to produce a runtime test. If that
weren't there, it would be kosher to fold away the test--but it should succeed
rather than fail. The actual address computed is correct and at runtime in the
debugger it can be seen to be 0 mod 16, so if the code checked that as it
should the test would pass.

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