[llvm-bugs] [Bug 28417] New: missing tailcall optimization

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28417

            Bug ID: 28417
           Summary: missing tailcall optimization
           Product: libraries
           Version: 3.8
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Common Code Generator Code
          Assignee: unassignedbugs at nondot.org
          Reporter: vanyacpp at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

For this code LLVM generates code that doesn't use tailcall optimization.

struct token
{
    char const* tok_start;
    char const* tok_end;
    int tok_type;
    unsigned identifier_hash;
};

token f();

token g()
{
  return f();
}

Generated code:

g():                                  # @g()
        pushq   %rbx
        movq    %rdi, %rbx
        callq   f()
        movq    %rbx, %rax
        popq    %rbx
        retq



Expected code:

g():                                  # @g()
        jmpq    f()

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