Add chibicc

This program popped up on Hacker News recently. It's the only modern
compiler I've ever seen that doesn't have dependencies and is easily
modified. So I added all of the missing GNU extensions I like to use
which means it might be possible soon to build on non-Linux and have
third party not vendor gcc binaries.

third_party/chibicc/fpclassify.c

@@ -0,0 +1,145 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 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 "third_party/chibicc/chibicc.h"
+
+/**
+ * @fileoverview __builtin_fpclassify() implementation
+ */
+
+#define FPCLASSIFY_FLOAT \
+  "\tmovaps\t%%xmm0,%%xmm1\n\
+\tmov\t$0x7fffffff,%%eax\n\
+\tmovd\t%%eax,%%xmm2\n\
+\tandps\t%%xmm2,%%xmm1\n\
+\tmov\t$%d,%%eax\n\
+\tucomiss\t%%xmm1,%%xmm1\n\
+\tjp\t9f\n\
+\tmov\t$0x7f7fffff,%%edi\n\
+\tmovd\t%%edi,%%xmm2\n\
+\tucomiss\t%%xmm2,%%xmm1\n\
+\tja\t2f\n\
+\tmov\t$0x00800000,%%edi\n\
+\tmovd\t%%edi,%%xmm2\n\
+\tucomiss\t%%xmm2,%%xmm1\n\
+\tjnb\t3f\n\
+\txorps\t%%xmm1,%%xmm1\n\
+\tucomiss\t%%xmm1,%%xmm0\n\
+\tjp\t1f\n\
+\tmovl\t$%d,%%eax\n\
+\tje\t9f\n\
+1:\tmovl\t$%d,%%eax\n\
+\tjmp\t9f\n\
+2:\tmovl\t$%d,%%eax\n\
+\tjmp\t9f\n\
+3:\tmovl\t$%d,%%eax\n\
+9:"
+
+#define FPCLASSIFY_DOUBLE \
+  "\tmovapd\t%%xmm0,%%xmm1\n\
+\tmov\t$0x7fffffffffffffff,%%rax\n\
+\tmovq\t%%rax,%%xmm2\n\
+\tandps\t%%xmm2,%%xmm1\n\
+\tmov\t$%d,%%eax\n\
+\tucomisd\t%%xmm1,%%xmm1\n\
+\tjp\t9f\n\
+\tmov\t$0x7fefffffffffffff,%%rdi\n\
+\tmovq\t%%rdi,%%xmm2\n\
+\tucomisd\t%%xmm2,%%xmm1\n\
+\tja\t2f\n\
+\tmov\t$0x0010000000000000,%%rdi\n\
+\tmovq\t%%rdi,%%xmm2\n\
+\tucomisd\t%%xmm2,%%xmm1\n\
+\tjnb\t3f\n\
+\txorps\t%%xmm1,%%xmm1\n\
+\tucomisd\t%%xmm1,%%xmm0\n\
+\tjp\t1f\n\
+\tmovl\t$%d,%%eax\n\
+\tje\t9f\n\
+1:\tmovl\t$%d,%%eax\n\
+\tjmp\t9f\n\
+2:\tmovl\t$%d,%%eax\n\
+\tjmp\t9f\n\
+3:\tmovl\t$%d,%%eax\n\
+9:"
+
+#define FPCLASSIFY_LDOUBLE \
+  "\tmov\t$%d,%%eax\n\
+\tfld\t%%st\n\
+\tfabs\n\
+\tfucomi\t%%st,%%st\n\
+\tjp\t6f\n\
+\tpush\t$0x7ffe\n\
+\tpush\t$-1\n\
+\tfldt\t(%%rsp)\n\
+\tadd\t$16,%%rsp\n\
+\tfxch\n\
+\tmov\t$%d,%%eax\n\
+\tfucomi\n\
+\tfstp\t%%st(1)\n\
+\tja\t7f\n\
+\tmov\t$1,%%edi\n\
+\tpush\t%%rdi\n\
+\tror\t%%rdi\n\
+\tpush\t%%rdi\n\
+\tfldt\t(%%rsp)\n\
+\tadd\t$16,%%rsp\n\
+\tfxch\n\
+\tmov\t$%d,%%eax\n\
+\tfucomip\n\
+\tfstp\t%%st\n\
+\tjnb\t8f\n\
+\tfldz\n\
+\tfxch\n\
+\tfucomip\n\
+\tfstp\t%%st\n\
+\tjp\t5f\n\
+\tmov\t$%d,%%eax\n\
+\tje\t9f\n\
+5:\tmov\t$%d,%%eax\n\
+\tjmp\t9f\n\
+6:\tfstp\t%%st\n\
+\tfstp\t%%st\n\
+\tjmp\t9f\n\
+7:\tfstp\t%%st\n\
+\tfstp\t%%st\n\
+\tjmp\t9f\n\
+8:\tfstp\t%%st\n\
+9:"
+
+void gen_fpclassify(FpClassify *fpc) {
+  int fpnan = fpc->args[0];
+  int fpinf = fpc->args[1];
+  int fpnorm = fpc->args[2];
+  int fpsubnorm = fpc->args[3];
+  int fpzero = fpc->args[4];
+  gen_expr(fpc->node);
+  switch (fpc->node->ty->kind) {
+    case TY_FLOAT:
+      println(FPCLASSIFY_FLOAT, fpnan, fpzero, fpsubnorm, fpinf, fpnorm);
+      break;
+    case TY_DOUBLE:
+      println(FPCLASSIFY_DOUBLE, fpnan, fpzero, fpsubnorm, fpinf, fpnorm);
+      break;
+    case TY_LDOUBLE:
+      println(FPCLASSIFY_LDOUBLE, fpnan, fpinf, fpnorm, fpzero, fpsubnorm);
+      break;
+    default:
+      UNREACHABLE();
+  }
+}