[llvm-bugs] [Bug 44212] New: Type pruning not working when casting/indirection is used

via llvm-bugs llvm-bugs at lists.llvm.org
Tue Dec 3 10:51:19 PST 2019


            Bug ID: 44212
           Summary: Type pruning not working when casting/indirection is
           Product: clang
           Version: 8.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: Stan.Kvasov at mediatek.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

Created attachment 22887
  --> https://bugs.llvm.org/attachment.cgi?id=22887&action=edit

Clang emits incorrect TBAA information when accessing a union member with any
kind of casting. In the example attached, r.w[i] gets the right TBAA type info
of omnipotent char. Any other access like ((int*)r.w)[i] or *(r.w + i) gets
TBAA int type. This leads to incorrect optimization as shown in the attachment.

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