Improve dead code elimination

libc/sysv/consts/syscon.internal.h

@@ -0,0 +1,66 @@
+/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8     -*-│
+│vi: set et ft=asm ts=8 tw=8 fenc=utf-8                                     :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/dce.h"
+#include "libc/macros.h"
+
+.macro	.syscon	group:req name:req linux:req xnu:req freebsd:req openbsd:req netbsd:req windows:req
+	yoink	_init_systemfive
+
+	.section .piro.bss.sort.syscon.2.\group\().\name,"aw",@nobits
+\name:	.quad	0
+	.endobj	\name,globl
+	.previous
+
+#if SupportsLinux()
+	.section .sort.rodata.syscon.linux.2.\group\().\name,"a",@progbits
+	.sleb128 \linux
+	.previous
+#endif
+
+#if SupportsXnu()
+	.section .sort.rodata.syscon.xnu.2.\group\().\name,"a",@progbits
+	.sleb128 \xnu
+	.previous
+#endif
+
+#if SupportsFreebsd()
+	.section .sort.rodata.syscon.freebsd.2.\group\().\name,"a",@progbits
+	.sleb128 \freebsd
+	.previous
+#endif
+
+#if SupportsOpenbsd()
+	.section .sort.rodata.syscon.openbsd.2.\group\().\name,"a",@progbits
+	.sleb128 \openbsd
+	.previous
+#endif
+
+#if SupportsNetbsd()
+	.section .sort.rodata.syscon.netbsd.2.\group\().\name,"a",@progbits
+	.sleb128 \netbsd
+	.previous
+#endif
+
+#if SupportsWindows()
+	.section .sort.rodata.syscon.windows.2.\group\().\name,"a",@progbits
+	.sleb128 \windows
+	.previous
+#endif
+
+.endm