From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 197CA3846403; Fri, 16 Apr 2021 01:51:57 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 197CA3846403 From: "hewillk at gmail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/100104] std::transform is 1.5 times faster than std::copy with -O3 Date: Fri, 16 Apr 2021 01:51:56 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Version: 11.0 X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: hewillk at gmail dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Resolution: X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: gcc-bugs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-bugs mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 16 Apr 2021 01:51:57 -0000 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D100104 --- Comment #4 from =E5=BA=B7=E6=A1=93=E7=91=8B = --- And Build "copy" with -O2 on ARM64 is identical with -O3 (https://godbolt.org/z/5hjKGbrTd): .LC0: .string "vector::_M_realloc_insert" transform(std::vector > const&): stp x29, x30, [sp, -64]! mov x29, sp stp x19, x20, [sp, 16] mov x19, x8 ldp x20, x0, [x0] stp xzr, xzr, [x8] str xzr, [x8, 16] sub x0, x0, x20 cmp x0, 0 ble .L19 mov x1, 0 str x21, [sp, 32] asr x21, x0, 3 mov x0, 0 b .L23 .L35: str w2, [x0], 4 add x20, x20, 8 subs x21, x21, #1 str x0, [x19, 8] beq .L34 .L36: ldp x0, x1, [x19, 8] .L23: ldr d0, [x20] fcvtzs w2, d0 str w2, [sp, 60] cmp x1, x0 bne .L35 add x2, sp, 60 mov x0, x19 bl void std::vector >::_M_realloc_insert(__gnu_cxx::__normal_iterator > >, int&&) add x20, x20, 8 subs x21, x21, #1 bne .L36 .L34: ldr x21, [sp, 32] .L19: mov x0, x19 ldp x19, x20, [sp, 16] ldp x29, x30, [sp], 64 ret ldr x2, [x19] ldr x1, [x19, 16] mov x19, x0 sub x1, x1, x2 cbz x2, .L25 mov x0, x2 bl operator delete(void*, unsigned long) .L25: mov x0, x19 bl _Unwind_Resume DW.ref.__gxx_personality_v0: .xword __gxx_personality_v0 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D However, "transform" has been further optimized under -O3 (https://godbolt.org/z/5hjKGbrTd): .LC0: .string "vector::_M_realloc_insert" transform(std::vector > const&): stp x29, x30, [sp, -96]! mov x29, sp stp x19, x20, [sp, 16] stp x21, x22, [sp, 32] mov x21, x8 ldp x20, x22, [x0] stp xzr, xzr, [x8] str xzr, [x8, 16] cmp x22, x20 beq .L1 mov x19, 0 stp x23, x24, [sp, 48] stp x25, x26, [sp, 64] mov x25, 2305843009213693951 stp x27, x28, [sp, 80] mov x28, 0 b .L13 .L32: str w27, [x19], 4 add x20, x20, 8 str x19, [x21, 8] cmp x22, x20 beq .L31 .L13: ldr d0, [x20] fcvtzs w27, d0 cmp x19, x28 bne .L32 ldr x24, [x21] sub x23, x19, x24 asr x1, x23, 2 cmp x1, x25 beq .L33 cmp x1, 0 csinc x0, x1, xzr, ne adds x0, x0, x1 bcs .L7 cbnz x0, .L34 mov x28, 0 mov x26, 0 .L9: add x19, x23, 4 str w27, [x26, x23] add x19, x26, x19 cmp x23, 0 bgt .L35 cbnz x24, .L36 .L12: add x20, x20, 8 stp x26, x19, [x21] str x28, [x21, 16] cmp x22, x20 bne .L13 .L31: ldp x23, x24, [sp, 48] ldp x25, x26, [sp, 64] ldp x27, x28, [sp, 80] .L1: mov x0, x21 ldp x19, x20, [sp, 16] ldp x21, x22, [sp, 32] ldp x29, x30, [sp], 96 ret .L35: mov x1, x24 mov x2, x23 mov x0, x26 bl memmove ldr x1, [x21, 16] sub x1, x1, x24 .L11: mov x0, x24 bl operator delete(void*, unsigned long) b .L12 .L36: ldr x1, [x21, 16] sub x1, x1, x24 b .L11 .L34: cmp x0, x25 csel x0, x0, x25, ls lsl x28, x0, 2 .L8: mov x0, x28 bl operator new(unsigned long) mov x26, x0 add x28, x0, x28 b .L9 .L7: mov x28, 9223372036854775804 b .L8 .L33: adrp x0, .LC0 add x0, x0, :lo12:.LC0 bl std::__throw_length_error(char const*) ldr x2, [x21] mov x19, x0 ldr x1, [x21, 16] sub x1, x1, x2 cbz x2, .L16 mov x0, x2 bl operator delete(void*, unsigned long) .L16: mov x0, x19 bl _Unwind_Resume DW.ref.__gxx_personality_v0: .xword __gxx_personality_v0=