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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/115534] intermediate stack use not eliminated
Date: Tue, 18 Jun 2024 17:26:44 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D115534

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-06-18
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.

Note even without vectorizer turned on we get really bad code from the retu=
rn
when expanding (just happens the RTL optimizers can remove the load/stores =
but
not the stack location):
```

;; return D.4535;

(insn 60 59 61 (set (reg:DF 156)
        (mem/c:DF (plus:DI (reg/f:DI 95 virtual-stack-vars)
                (const_int -32 [0xffffffffffffffe0])) [4 D.4535+0 S8 A128]))
"/app/example.cpp":24:12 -1
     (nil))

(insn 61 60 62 (set (reg:DF 157)
        (mem/c:DF (plus:DI (reg/f:DI 95 virtual-stack-vars)
                (const_int -24 [0xffffffffffffffe8])) [4 D.4535+8 S8 A64]))
"/app/example.cpp":24:12 -1
     (nil))

(insn 62 61 63 (set (reg:DF 158)
        (mem/c:DF (plus:DI (reg/f:DI 95 virtual-stack-vars)
                (const_int -16 [0xfffffffffffffff0])) [4 D.4535+16 S8 A128]=
))
"/app/example.cpp":24:12 -1
     (nil))

(insn 63 62 64 (set (reg:DF 159)
        (mem/c:DF (plus:DI (reg/f:DI 95 virtual-stack-vars)
                (const_int -8 [0xfffffffffffffff8])) [4 D.4535+24 S8 A64]))
"/app/example.cpp":24:12 -1
     (nil))

(insn 64 63 65 (set (reg:DF 132 [ <retval> ])
        (reg:DF 156)) "/app/example.cpp":24:12 -1
     (nil))

(insn 65 64 66 (set (reg:DF 133 [ <retval>+8 ])
        (reg:DF 157)) "/app/example.cpp":24:12 -1
     (nil))

(insn 66 65 67 (set (reg:DF 134 [ <retval>+16 ])
        (reg:DF 158)) "/app/example.cpp":24:12 -1
     (nil))

(insn 67 66 68 (set (reg:DF 135 [ <retval>+24 ])
        (reg:DF 159)) "/app/example.cpp":24:12 -1
     (nil))

(jump_insn 68 67 69 (set (pc)
        (label_ref 0)) "/app/example.cpp":24:12 -1
     (nil))
```

On the stack location we get:
```
        sub     sp, sp, #64
```

This is why I said there are a few duplicates there ...=