From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/10138 Path: news.gmane.org!not-for-mail From: Natanael Copa Newsgroups: gmane.linux.lib.musl.general Subject: Re: [PATCH 2/2] refactor name_from_dns Date: Wed, 15 Jun 2016 19:53:45 +0200 Message-ID: <20160615195345.1af40b40@ncopa-desktop.alpinelinux.org> References: <1464168134-17039-1-git-send-email-ncopa@alpinelinux.org> <1464168134-17039-2-git-send-email-ncopa@alpinelinux.org> <20160527044057.GB10893@brightrain.aerifal.cx> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1466013253 17352 80.91.229.3 (15 Jun 2016 17:54:13 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 15 Jun 2016 17:54:13 +0000 (UTC) Cc: musl@lists.openwall.com To: Rich Felker Original-X-From: musl-return-10151-gllmg-musl=m.gmane.org@lists.openwall.com Wed Jun 15 19:54:08 2016 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1bDF0y-0002B8-Do for gllmg-musl@m.gmane.org; Wed, 15 Jun 2016 19:54:08 +0200 Original-Received: (qmail 11523 invoked by uid 550); 15 Jun 2016 17:54:06 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 11499 invoked from network); 15 Jun 2016 17:54:05 -0000 In-Reply-To: <20160527044057.GB10893@brightrain.aerifal.cx> X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.28; x86_64-alpine-linux-musl) Xref: news.gmane.org gmane.linux.lib.musl.general:10138 Archived-At: On Fri, 27 May 2016 00:40:57 -0400 Rich Felker wrote: > On Wed, May 25, 2016 at 11:22:14AM +0200, Natanael Copa wrote: > > loop over an address family / resource record mapping to avoid > > repetitive code. > > --- > > src/network/lookup_name.c | 27 +++++++++++++-------------- > > 1 file changed, 13 insertions(+), 14 deletions(-) > > > > diff --git a/src/network/lookup_name.c b/src/network/lookup_name.c > > index d3d97b4..99364ab 100644 > > --- a/src/network/lookup_name.c > > +++ b/src/network/lookup_name.c > > @@ -141,20 +141,19 @@ static int name_from_dns(struct address buf[static MAXADDRS], char canon[static > > int qlens[2], alens[2]; > > int i, nq = 0; > > struct dpc_ctx ctx = { .addrs = buf, .canon = canon }; > > - > > - if (family != AF_INET6) { > > - qlens[nq] = __res_mkquery(0, name, 1, RR_A, 0, 0, 0, > > - qbuf[nq], sizeof *qbuf); > > - if (qlens[nq] == -1) > > - return EAI_NONAME; > > - nq++; > > - } > > - if (family != AF_INET) { > > - qlens[nq] = __res_mkquery(0, name, 1, RR_AAAA, 0, 0, 0, > > - qbuf[nq], sizeof *qbuf); > > - if (qlens[nq] == -1) > > - return EAI_NONAME; > > - nq++; > > + struct { int af; int rr; } afrr[2] = { > > + { .af = AF_INET6, .rr = RR_A }, > > + { .af = AF_INET, .rr = RR_AAAA }, > > + }; > > + > > + for (i=0; i<2; i++) { > > + if (family != afrr[i].af) { > > + qlens[nq] = __res_mkquery(0, name, 1, afrr[i].rr, > > + 0, 0, 0, qbuf[nq], sizeof *qbuf); > > + if (qlens[nq] == -1) > > + return EAI_NONAME; > > + nq++; > > + } > > Can you compare the codegen for this as written vs making the table > static-const? I wonder which gcc does better with. My guess would be > static-const is better if it actually emits the table and loops over > it, but auto storage like you did might be better if that helps it > just unroll it plugging in the values. as shown above (without static const) gcc will make it loop (there is only one call to __res_mkquery): name_from_dns: pushq %r15 pushq %r14 movq %rdi, %r9 pushq %r13 pushq %r12 movl %ecx, %r11d pushq %rbp pushq %rbx movl $6, %ecx movq %r8, %r10 xorl %r12d, %r12d xorl %ebp, %ebp subq $1720, %rsp leaq 128(%rsp), %r13 leaq 688(%rsp), %rbx leaq 104(%rsp), %rdi leaq 88(%rsp), %r14 movq %rdx, (%rsp) movl $10, 88(%rsp) leaq 280(%r13), %rax movq %r13, 56(%rsp) movq %rbx, 72(%rsp) movl $1, 92(%rsp) movl $2, 96(%rsp) movq %rax, 64(%rsp) leaq 512(%rbx), %rax movl $28, 100(%rsp) movq %rax, 80(%rsp) xorl %eax, %eax rep stosl leaq 104(%rsp), %rax movq %r9, 104(%rsp) movq %rsi, 112(%rsp) movq %rax, 8(%rsp) .L17: cmpl %r11d, (%r12,%r14) je .L14 movslq %ebp, %r15 movq %r10, 24(%rsp) movl %r11d, 20(%rsp) imulq $280, %r15, %rax pushq %rsi pushq $280 movl 4(%r14,%r12), %ecx xorl %r9d, %r9d xorl %r8d, %r8d xorl %edi, %edi movl $1, %edx addq %r13, %rax pushq %rax pushq $0 movq 32(%rsp), %rsi call __res_mkquery movl %eax, 72(%rsp,%r15,4) addq $32, %rsp incl %eax movl 20(%rsp), %r11d movq 24(%rsp), %r10 jne .L15 .L20: movl $-2, %edx jmp .L16 .L15: incl %ebp .L14: addq $8, %r12 cmpq $16, %r12 jne .L17 leaq 48(%rsp), %r12 leaq 72(%rsp), %rcx leaq 40(%rsp), %rdx leaq 56(%rsp), %rsi pushq %rax pushq %r10 movl $512, %r9d movq %r12, %r8 movl %ebp, %edi call __res_msend_rc xorl %r13d, %r13d testl %eax, %eax popq %rdx movl $-11, %edx popq %rcx js .L16 .L18: cmpl %r13d, %ebp jle .L31 movl (%r12,%r13,4), %esi movq 8(%rsp), %rcx leaq dns_parse_callback(%rip), %rdx movq %rbx, %rdi incq %r13 addq $512, %rbx call __dns_parse jmp .L18 .L31: movl 120(%rsp), %edx testl %edx, %edx jne .L16 cmpl $3, 48(%rsp) jle .L23 movb 691(%rsp), %al andl $15, %eax cmpb $2, %al je .L23 testb %al, %al je .L20 cmpb $3, %al movl $-4, %eax cmovne %eax, %edx jmp .L16 .L23: ... with "static const struct { int af; int rr; } afrr[2] = {" gcc will actually unroll it (there are 2 calls to __res_mkquery): name_from_dns: pushq %r15 pushq %r14 movq %rdi, %r9 pushq %r13 pushq %r12 movl %ecx, %r15d pushq %rbp pushq %rbx movl $6, %ecx movq %rdx, %r13 movq %r8, %r14 subq $1688, %rsp leaq 96(%rsp), %r12 leaq 656(%rsp), %rbx leaq 72(%rsp), %rdi leaq 280(%r12), %rax movq %r12, 40(%rsp) movq %rbx, 56(%rsp) movq %rax, 48(%rsp) leaq 512(%rbx), %rax movq %rax, 64(%rsp) xorl %eax, %eax cmpl $10, %r15d rep stosl leaq 72(%rsp), %rax movq %r9, 72(%rsp) movq %rsi, 80(%rsp) movq %rax, 8(%rsp) je .L21 pushq %rdi pushq $280 xorl %r9d, %r9d pushq %r12 pushq $0 xorl %r8d, %r8d xorl %edi, %edi movl $1, %ecx movl $1, %edx movq %r13, %rsi call __res_mkquery movl %eax, 56(%rsp) addq $32, %rsp incl %eax je .L15 cmpl $2, %r15d movl $1, %ebp jne .L36 jmp .L16 .L21: xorl %ebp, %ebp .L36: movslq %ebp, %r15 pushq %rsi pushq $280 imulq $280, %r15, %rax xorl %r9d, %r9d xorl %r8d, %r8d xorl %edi, %edi movl $28, %ecx movl $1, %edx movq %r13, %rsi incl %ebp addq %rax, %r12 pushq %r12 pushq $0 call __res_mkquery movl %eax, 56(%rsp,%r15,4) addq $32, %rsp incl %eax jne .L16 .L15: movl $-2, %edx jmp .L18 .L16: leaq 32(%rsp), %r12 leaq 56(%rsp), %rcx leaq 24(%rsp), %rdx leaq 40(%rsp), %rsi pushq %rax pushq %r14 movl $512, %r9d movq %r12, %r8 movl %ebp, %edi call __res_msend_rc xorl %r14d, %r14d testl %eax, %eax popq %rdx movl $-11, %edx popq %rcx js .L18 .L19: cmpl %r14d, %ebp jle .L38 movl (%r12,%r14,4), %esi movq 8(%rsp), %rcx leaq dns_parse_callback(%rip), %rdx movq %rbx, %rdi incq %r14 addq $512, %rbx call __dns_parse jmp .L19 .L38: movl 88(%rsp), %edx testl %edx, %edx jne .L18 cmpl $3, 32(%rsp) jle .L24 movb 659(%rsp), %al andl $15, %eax cmpb $2, %al je .L24 testb %al, %al je .L15 cmpb $3, %al movl $-4, %eax cmovne %eax, %edx jmp .L18 .L24: > > Rich