From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from loongson.cn (mail.loongson.cn [114.242.206.163]) by sourceware.org (Postfix) with ESMTP id 61BFE38582B6 for ; Sun, 31 Jul 2022 09:05:29 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 61BFE38582B6 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=loongson.cn Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=loongson.cn Received: from [10.20.4.210] (unknown [10.20.4.210]) by mail.loongson.cn (Coremail) with SMTP id AQAAf9DxX9LUReZi7WtGAA--.34014S2; Sun, 31 Jul 2022 17:05:24 +0800 (CST) Subject: Re: [PATCH v3] LoongArch: add addr_global attribute To: Xi Ruoyao , gcc-patches@gcc.gnu.org, Lulu Cheng Cc: Youling Tang , Huacai Chen , Jinyang He , Wang Xuerui References: <9b6b0e68cfb7e87ae961ef8a7bb7987f534da19c.camel@xry111.site> From: Chenghua Xu Message-ID: Date: Sun, 31 Jul 2022 17:05:24 +0800 User-Agent: Mozilla/5.0 (X11; Linux loongarch64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <9b6b0e68cfb7e87ae961ef8a7bb7987f534da19c.camel@xry111.site> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-CM-TRANSID: AQAAf9DxX9LUReZi7WtGAA--.34014S2 X-Coremail-Antispam: 1UD129KBjvJXoW3GF1xtrW3trW5WF1kGFyDZFb_yoW3AF1fpa 9ruFy5tw48JFs7WF9rJ3W3Wrn5WwsxWFy7W3W3Kr18Cayav3s7ZF18Kws0qanrJw1rGwnr Xr1j9w17uayY937anT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUvq14x267AKxVW8JVW5JwAFc2x0x2IEx4CE42xK8VAvwI8IcIk0 rVWrJVCq3wAFIxvE14AKwVWUJVWUGwA2ocxC64kIII0Yj41l84x0c7CEw4AK67xGY2AK02 1l84ACjcxK6xIIjxv20xvE14v26r1j6r1xM28EF7xvwVC0I7IYx2IY6xkF7I0E14v26r1j 6r4UM28EF7xvwVC2z280aVAFwI0_Cr0_Gr1UM28EF7xvwVC2z280aVCY1x0267AKxVW8Jr 0_Cr1UM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj 6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr 0_Gr1lF7xvr2IY64vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7Mxk0xIA0c2IEe2xFo4CE bIxvr21lc2xSY4AK6svPMxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI 8I3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AK xVWUAVWUtwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI 8IcVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_WFyUJVCq3wCI42IY6I8E 87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I0E14v26r1j6r4UYxBIdaVFxhVjvjDU0x ZFpf9x0JUdHUDUUUUU= X-CM-SenderInfo: x0xfxv5qjk3to6or00hjvr0hdfq/ X-Spam-Status: No, score=-12.4 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, KAM_SHORT, KAM_STOCKGEN, NICE_REPLY_A, SPF_HELO_PASS, SPF_PASS, 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 X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 31 Jul 2022 09:05:32 -0000 在 2022/7/30 上午1:17, Xi Ruoyao via Gcc-patches 写道: > Change v2 to v3: > - Disable section anchor for addr_global symbols. > - Use -O2 in test to make sure section anchor is disabled. > > -- > > Background: > https://lore.kernel.org/loongarch/d7670b60-2782-4642-995b-7baa01779a66@loongson.cn/T/#e1d47e2fe185f2e2be8fdc0784f0db2f644119379 > > Question: Do you have a better name than "addr_global"? > > Alternatives: > > 1. Just use "-mno-explicit-relocs -mla-local-with-abs" for kernel > modules. It's stupid IMO. > 2. Implement a "-maddress-local-with-got" option for GCC and use it for > kernel modules. It seems too overkill: we might create many unnecessary > GOT entries. > 3. For all variables with a section attribute, consider it global. It > may make sense, but I just checked x86_64 and riscv and they don't do > this. > 4. Implement -mcmodel=extreme and use it for kernel modules. To me > "extreme" seems really too extreme. > 5. More hacks in kernel. (Convert relocations against .data..percpu with > objtool? But objtool is not even implemented for LoongArch yet.) > > Note: I'll be mostly AFK in the following week. My attempt to finish > the kernel support for new relocs before going AFK now failed miserably > :(. > > -- >8 -- > > A linker script and/or a section attribute may locate a local object in > some way unexpected by the code model, leading to a link failure. This > happens when the Linux kernel loads a module with "local" per-CPU > variables. > > Add an attribute to explicitly mark an variable with the address > unlimited by the code model so we would be able to work around such > problems. > > gcc/ChangeLog: > > * config/loongarch/loongarch.cc (loongarch_attribute_table): > New attribute table. > (TARGET_ATTRIBUTE_TABLE): Define the target hook. > (loongarch_handle_addr_global_attribute): New static function. > (loongarch_classify_symbol): Return SYMBOL_GOT_DISP for > SYMBOL_REF_DECL with addr_global attribute. > (loongarch_use_anchors_for_symbol_p): New static function. > (TARGET_USE_ANCHORS_FOR_SYMBOL_P): Define the target hook. > * doc/extend.texi (Variable Attributes): Document new > LoongArch specific attribute. > > gcc/testsuite/ChangeLog: > > * gcc.target/loongarch/addr-global.c: New test. > --- > gcc/config/loongarch/loongarch.cc | 61 +++++++++++++++++++ > gcc/doc/extend.texi | 17 ++++++ > .../gcc.target/loongarch/addr-global.c | 28 +++++++++ > 3 files changed, 106 insertions(+) > create mode 100644 gcc/testsuite/gcc.target/loongarch/addr-global.c > > diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc > index 79687340dfd..db6f84d4e66 100644 > --- a/gcc/config/loongarch/loongarch.cc > +++ b/gcc/config/loongarch/loongarch.cc > @@ -1643,6 +1643,13 @@ loongarch_classify_symbol (const_rtx x) > && !loongarch_symbol_binds_local_p (x)) > return SYMBOL_GOT_DISP; > > + if (SYMBOL_REF_P (x)) > + { > + tree decl = SYMBOL_REF_DECL (x); > + if (decl && lookup_attribute ("addr_global", DECL_ATTRIBUTES (decl))) > + return SYMBOL_GOT_DISP; > + } > + > return SYMBOL_PCREL; > } > > @@ -6068,6 +6075,54 @@ loongarch_starting_frame_offset (void) > return crtl->outgoing_args_size; > } > > +static tree > +loongarch_handle_addr_global_attribute (tree *node, tree name, tree, int, > + bool *no_add_attrs) > +{ > + tree decl = *node; > + if (TREE_CODE (decl) == VAR_DECL) > + { > + if (DECL_CONTEXT (decl) > + && TREE_CODE (DECL_CONTEXT (decl)) == FUNCTION_DECL > + && !TREE_STATIC (decl)) > + { > + error_at (DECL_SOURCE_LOCATION (decl), > + "%qE attribute cannot be specified for local " > + "variables", name); > + *no_add_attrs = true; > + } > + } > + else > + { > + warning (OPT_Wattributes, "%qE attribute ignored", name); > + *no_add_attrs = true; > + } > + return NULL_TREE; > +} > + > +static const struct attribute_spec loongarch_attribute_table[] = > +{ > + /* { name, min_len, max_len, decl_req, type_req, fn_type_req, > + affects_type_identity, handler, exclude } */ > + { "addr_global", 0, 0, true, false, false, false, > + loongarch_handle_addr_global_attribute, NULL }, > + /* The last attribute spec is set to be NULL. */ > + {} > +}; > + > +bool > +loongarch_use_anchors_for_symbol_p (const_rtx symbol) > +{ > + tree decl = SYMBOL_REF_DECL (symbol); > + > + /* addr_global indicates we don't know how the linker will locate the symbol, > + so the use of anchor may cause relocation overflow. */ > + if (decl && lookup_attribute ("addr_global", DECL_ATTRIBUTES (decl))) > + return false; > + > + return default_use_anchors_for_symbol_p (symbol); > +} > + > /* Initialize the GCC target structure. */ > #undef TARGET_ASM_ALIGNED_HI_OP > #define TARGET_ASM_ALIGNED_HI_OP "\t.half\t" > @@ -6256,6 +6311,12 @@ loongarch_starting_frame_offset (void) > #undef TARGET_HAVE_SPECULATION_SAFE_VALUE > #define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed > > +#undef TARGET_ATTRIBUTE_TABLE > +#define TARGET_ATTRIBUTE_TABLE loongarch_attribute_table > + > +#undef TARGET_USE_ANCHORS_FOR_SYMBOL_P > +#define TARGET_USE_ANCHORS_FOR_SYMBOL_P loongarch_use_anchors_for_symbol_p > + > struct gcc_target targetm = TARGET_INITIALIZER; > > #include "gt-loongarch.h" > diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi > index 7fe7f8817cd..4a1cd7ab5e4 100644 > --- a/gcc/doc/extend.texi > +++ b/gcc/doc/extend.texi > @@ -7314,6 +7314,7 @@ attributes. > * Blackfin Variable Attributes:: > * H8/300 Variable Attributes:: > * IA-64 Variable Attributes:: > +* LoongArch Variable Attributes:: > * M32R/D Variable Attributes:: > * MeP Variable Attributes:: > * Microsoft Windows Variable Attributes:: > @@ -8098,6 +8099,22 @@ defined by shared libraries. > > @end table > > +@node LoongArch Variable Attributes > +@subsection LoongArch Variable Attributes > + > +One attribute is currently defined for the LoongArch. > + > +@table @code > +@item addr_global > +@cindex @code{addr_global} variable attribute, LoongArch > +@cindex variable addressability on the LoongArch Can't understand this, Copied and forget to changing? > +Use this attribute on the LoongArch to mark an object with address > +unlimited limited by the local data section range specified by the code > +model, even if the object is defined locally. This attribute is mostly > +useful if a @code{section} attribute or a linker script will move the > +object somewhere unexpected by the code model. > +@end table > + > @node M32R/D Variable Attributes > @subsection M32R/D Variable Attributes > > diff --git a/gcc/testsuite/gcc.target/loongarch/addr-global.c b/gcc/testsuite/gcc.target/loongarch/addr-global.c > new file mode 100644 > index 00000000000..46a895c84bb > --- /dev/null > +++ b/gcc/testsuite/gcc.target/loongarch/addr-global.c > @@ -0,0 +1,28 @@ > +/* addr_global attribute should mark x and y possibly outside of the local > + data range defined by the code model, so GOT should be used instead of > + PC-relative. */ > + > +/* { dg-do compile } */ > +/* { dg-options "-mexplicit-relocs -mcmodel=normal -O2" } */ > +/* { dg-final { scan-assembler-not "%pc" } } */ > +/* { dg-final { scan-assembler-times "%got_pc_hi20" 3 } } */ > + > +int x __attribute__((addr_global)); > +int y __attribute__((addr_global)); > + > +int > +test(void) > +{ > + return x + y; > +} > + > +/* The following will be used for kernel per-cpu storage implemention. */ > + > +register char *per_cpu_base __asm__("r21"); > +static int counter __attribute__((section(".data..percpu"), addr_global)); > +void > +inc_counter(void) > +{ > + int *ptr = (int *)(per_cpu_base + (long)&counter); > + (*ptr)++; > +}