[llvm-bugs] [Bug 50117] New: Missed opportunity to use tail calls

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50117

            Bug ID: 50117
           Summary: Missed opportunity to use tail calls
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: david.bolvansky at gmail.com
                CC: llvm-bugs at lists.llvm.org

void foo (char *, int n);
int bar (int);
int baz (char *p);

int
test1 (int n)
{
  {
    char buf[64];
    foo (buf, n);
  }
  return bar (n);
}

void
test2 (char *p)
{
  {
    char c;
    baz (&c);
  }
  baz (p);
}

test1:                                  # @test1
        push    rbx
        sub     rsp, 64
        mov     ebx, edi
        mov     rdi, rsp
        mov     esi, ebx
        call    foo
        mov     edi, ebx
        call    bar // can be jmp bar
        add     rsp, 64
        pop     rbx
        ret
test2:                                  # @test2
        push    rbx
        sub     rsp, 16
        mov     rbx, rdi
        lea     rdi, [rsp + 15]
        call    baz
        mov     rdi, rbx
        call    baz // can be jmp baz
        add     rsp, 16
        pop     rbx
        ret


https://godbolt.org/z/TvM81eYod

In IR I see that we have just call, not "tail call", so a middle-end issue.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20210425/205b2f19/attachment.html>