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From: "ubizjak at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/109079] Missing optimization for x86 avx intrinsic _mm256_zeroall(). Date: Thu, 09 Mar 2023 22:20:26 +0000 [thread overview] Message-ID: <bug-109079-4-4Ff5BvyFCj@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-109079-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109079 Uroš Bizjak <ubizjak at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Component|target |rtl-optimization --- Comment #2 from Uroš Bizjak <ubizjak at gmail dot com> --- (In reply to Richard Biener from comment #1) > I think it wasn't intended to be used this way, but sure. Currently it's a > black-box in the target I think and so nothing sees the redundancy. _mm256_zeroall is emitted as: (insn 6 3 7 2 (parallel [ (unspec_volatile [ (const_int 0 [0]) ] UNSPECV_VZEROALL) (set (reg:V8SI 20 xmm0) (const_vector:V8SI [ (const_int 0 [0]) repeated x8 ])) (set (reg:V8SI 21 xmm1) (const_vector:V8SI [ (const_int 0 [0]) repeated x8 ])) ... (set (reg:V8SI 51 xmm15) (const_vector:V8SI [ (const_int 0 [0]) repeated x8 ])) ]) and _mm256_setzero_ps as: (insn 7 6 8 2 (set (reg:V8SF 83) (const_vector:V8SF [ (const_double:SF 0.0 [0x0.0p+0]) repeated x8 ])) There is mode mismatch between (insn 6) and (insn 7) so postreload CSE is not able to eliminate (insn 7). Using the following patch^w hack that changes the mode of vzeroall registers: --cut here-- diff --git a/gcc/config/i386/predicates.md b/gcc/config/i386/predicates.md index b4d9ab40ab9..cf15ca8f611 100644 --- a/gcc/config/i386/predicates.md +++ b/gcc/config/i386/predicates.md @@ -1737,9 +1737,9 @@ (define_predicate "vzeroall_operation" if (GET_CODE (elt) != SET || GET_CODE (SET_DEST (elt)) != REG - || GET_MODE (SET_DEST (elt)) != V8SImode + || GET_MODE (SET_DEST (elt)) != V8SFmode || REGNO (SET_DEST (elt)) != GET_SSE_REGNO (i) - || SET_SRC (elt) != CONST0_RTX (V8SImode)) + || SET_SRC (elt) != CONST0_RTX (V8SFmode)) return false; } return true; diff --git a/gcc/config/i386/sse.md b/gcc/config/i386/sse.md index 172ec3bea4f..81e02086606 100644 --- a/gcc/config/i386/sse.md +++ b/gcc/config/i386/sse.md @@ -25244,8 +25244,8 @@ (define_expand "avx_vzeroall" for (regno = 0; regno < nregs; regno++) XVECEXP (operands[0], 0, regno + 1) - = gen_rtx_SET (gen_rtx_REG (V8SImode, GET_SSE_REGNO (regno)), - CONST0_RTX (V8SImode)); + = gen_rtx_SET (gen_rtx_REG (V8SFmode, GET_SSE_REGNO (regno)), + CONST0_RTX (V8SFmode)); }) (define_insn "*avx_vzeroall" --cut here-- the compiler is able to eliminate (insn 7) in postreload pass, producing: fn: vzeroall vmovups %ymm0, (%rdi) vzeroupper ret It looks to me that postreload CSE should be taught about the equivalence of vector modes - a V8SFmode zero has the same bit representation as V8SImode zero (and V4DImode, ...), as long as the mode size is the same. Recategorizing as rtl-optimization.
prev parent reply other threads:[~2023-03-09 22:20 UTC|newest] Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-03-09 10:26 [Bug target/109079] New: " dorazzsoft at gmail dot com 2023-03-09 12:37 ` [Bug target/109079] " rguenth at gcc dot gnu.org 2023-03-09 17:40 ` pinskia at gcc dot gnu.org 2023-03-09 22:20 ` ubizjak at gmail dot com [this message]
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