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From: "unlvsur at live dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107502] New: GCC fails to detect
 foo(first_const,last)-first_const+first pattern
Date: Tue, 01 Nov 2022 19:34:13 +0000
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X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
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X-Bugzilla-Who: unlvsur at live dot com
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107502

            Bug ID: 107502
           Summary: GCC fails to detect
                    foo(first_const,last)-first_const+first pattern
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: unlvsur at live dot com
  Target Milestone: ---

GCC fails to detect foo(first_const,last)-first_const+first pattern.

This is to use C++ std::contiguous_iterator interfaces with char const*
foo(char const* first, char const* last) noexcept; like APIs. However, GCC
fails to detect they are the same in IR and make them tail calls.

See godbolt:

https://godbolt.org/z/67PvYPar8=