From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 83D08385841D for ; Mon, 17 Oct 2022 13:00:45 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 83D08385841D Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666011645; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type; bh=0pF0Zn+7Oegb0R6wtL/4/apOr3Zib8Mswvm/hFXlA1k=; b=K8RvgTSa9jX3NR1Xd6Z4rk5U/V3gxC4eSYLzr6rXImzHfcBw4iWClP/tfQoWn0heLFuO96 SMAM9MVUwXQc/kJU7ZOoLTmZNY6aKS9Xn0Y3x84mB6AQLXIEExoYFyuEjvtXNy2xulraKI 5Xuc6a5UJoNIXTKuILFE/JNfl6HUcas= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-620-cCgJS7GbNg2m-jUAogaKMg-1; Mon, 17 Oct 2022 09:00:40 -0400 X-MC-Unique: cCgJS7GbNg2m-jUAogaKMg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 7D21F3814943 for ; Mon, 17 Oct 2022 13:00:40 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.193.168]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 16F0C2166B29 for ; Mon, 17 Oct 2022 13:00:39 +0000 (UTC) From: Florian Weimer To: gcc-patches@gcc.gnu.org Subject: [PATCH] libgcc: Mostly vectorize CIE encoding extraction for FDEs Date: Mon, 17 Oct 2022 15:00:38 +0200 Message-ID: <87edv6mwp5.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-11.3 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: "zR" and "zPLR" are the most common augmentations. Use a simple SIMD-with-in-a-register technique to check for both augmentations, and that the following variable-length integers have length 1, to get more quickly at the encoding field. libgcc/ * unwind-dw2-fde.c (get_cie_encoding_slow): Rename from get_cie_encoding. Mark as noinline. (get_cie_encoding): Add fast path for "zR" and "zPLR" augmentations. Call get_cie_encoding_slow as a fall-back. --- libgcc/unwind-dw2-fde.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 59 insertions(+), 2 deletions(-) diff --git a/libgcc/unwind-dw2-fde.c b/libgcc/unwind-dw2-fde.c index 3c0cc654ec0..4e3a54c5a1a 100644 --- a/libgcc/unwind-dw2-fde.c +++ b/libgcc/unwind-dw2-fde.c @@ -333,8 +333,10 @@ base_from_object (unsigned char encoding, const struct object *ob) /* Return the FDE pointer encoding from the CIE. */ /* ??? This is a subset of extract_cie_info from unwind-dw2.c. */ -static int -get_cie_encoding (const struct dwarf_cie *cie) +/* Disable inlining because the function is only used as a slow path in + get_cie_encoding below. */ +static int __attribute__ ((noinline)) +get_cie_encoding_slow (const struct dwarf_cie *cie) { const unsigned char *aug, *p; _Unwind_Ptr dummy; @@ -389,6 +391,61 @@ get_cie_encoding (const struct dwarf_cie *cie) } } +static inline int +get_cie_encoding (const struct dwarf_cie *cie) +{ + /* Fast path for some augmentations and single-byte variable-length + integers. Do this only for targets that align struct dwarf_cie to 8 + bytes, which ensures that at least 8 bytes are available starting at + cie->version. */ +#if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ \ + || __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ + if (__alignof (*cie) == 8 && sizeof (unsigned long long) == 8) + { + unsigned long long value = *(const unsigned long long *) &cie->version; + +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ +#define C(x) __builtin_bswap64 (x) +#else +#define C(x) x +#endif + + /* Fast path for "zR". Check for version 1, the "zR" string and that + the sleb128/uleb128 values are single bytes. In the comments + below, '1', 'c', 'd', 'r', 'l' are version, code alignment, data + alignment, return address column, augmentation length. Note that + with CIE version 1, the return address column is byte-encoded. */ + unsigned long long expected = + /* 1 z R 0 c d r l. */ + C (0x017a520000000000ULL); + unsigned long long mask = + /* 1 z R 0 c d r l. */ + C (0xffffffff80800080ULL); + + if ((value & mask) == expected) + return cie->augmentation[7]; + + /* Fast path for "zPLR". */ + expected = + /* 1 z P L R 0 c d. */ + C (0x017a504c52000000ULL); + mask = + /* 1 z P L R 0 c d. */ + C (0xffffffffffff8080ULL); +#undef C + + /* Validate the augmentation length, and return the enconding after + it. No check for the return address column because it is + byte-encoded with CIE version 1. */ + if (__builtin_expect ((value & mask) == expected + && (cie->augmentation[8] & 0x80) == 0, 1)) + return cie->augmentation[9]; + } +#endif + + return get_cie_encoding_slow (cie); +} + static inline int get_fde_encoding (const struct dwarf_fde *f) { base-commit: de84a1e4b107b803ec3b064c3771a6ed8c0e201e