From a1dabb4792446538cce24eb87bcd3ccb3c09f18b Mon Sep 17 00:00:00 2001
From: Xavier Leroy <xavier.leroy@college-de-france.fr>
Date: Tue, 27 Sep 2022 12:31:07 +0200
Subject: Handle unstructured 'switch' statements such as Duff's device

- New elaboration pass: SwitchNorm
    - recognizes structured 'switch' statements and puts them in a
      normalized form;
    - if selected, transforms unstructured 'switch' statements into a
      structured switch with goto actions + the original switch body
      with appropriate labels and gotos.

- C2C treatment of 'switch' statements is simplified accordingly.

- New language support option `-funstructured-switch`.

- Some tests were added (test/regression/switch3.c).
---
 test/regression/switch3.c | 182 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 182 insertions(+)
 create mode 100644 test/regression/switch3.c

(limited to 'test/regression/switch3.c')

diff --git a/test/regression/switch3.c b/test/regression/switch3.c
new file mode 100644
index 00000000..f411a3fb
--- /dev/null
+++ b/test/regression/switch3.c
@@ -0,0 +1,182 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+/* Unstructured switch statements */
+
+/* Duff's device */
+
+void send(char * to, char * from, int count)
+{
+  register int n = (count + 7) / 8;
+  switch (count % 8) {
+    case 0: do { *to++ = *from++;
+    case 7:      *to++ = *from++;
+    case 6:      *to++ = *from++;
+    case 5:      *to++ = *from++;
+    case 4:      *to++ = *from++;
+    case 3:      *to++ = *from++;
+    case 2:      *to++ = *from++;
+    case 1:      *to++ = *from++;
+            } while (--n > 0);
+  }
+}
+
+/* OpenBSD, usr.bin/locale */
+
+void quotestring(char * value, int double_quoted)
+{
+  char c;
+  while ((c = *value++) != '\0')
+    switch (c) {
+    case ' ': case '\t': case '\n': case '\'':
+    case '(': case ')': case '<': case '>':
+    case '&': case ';': case '|': case '~':
+      if (!double_quoted)
+    case '"': case '\\': case '$': case '`':
+        putchar('\\');
+    default:
+      putchar(c);
+      break;
+    }
+}
+
+/* Simon Tatham's coroutines */
+
+int nextchar(void)
+{
+  static unsigned char input[] = {
+    'a', 'b', 0xFF, 3, 'c', 'd', 0xFF, 2, 'e', '\n', 0
+  };
+  static unsigned char * next = input;
+  if (*next == 0)
+    return EOF;
+  else
+    return *next++;
+}
+
+#define crBegin static int state=0; switch(state) { case 0:
+#define crReturn(x) do { state=__LINE__; return x; \
+                         case __LINE__:; } while (0)
+#define crFinish }
+
+int decompressor(void) {
+  static int c, len;
+  crBegin;
+  while (1) {
+    c = nextchar();
+    if (c == EOF)
+      break;
+    if (c == 0xFF) {
+      len = nextchar();
+      c = nextchar();
+      while (len--)
+        crReturn(c);
+    } else
+      crReturn(c);
+  }
+  crReturn(EOF);
+  crFinish;
+}
+
+/* Pigeon's device */
+
+static enum { REVDFWDT, FORWARD, REVERSE } sorting_mode;
+
+#define DAYOF(stamp)  ((stamp) / 10000)
+#define TIMEOF(stamp) ((stamp) % 10000)
+
+static inline int intcmp(unsigned int x, unsigned int y)
+{
+  if (x < y) return -1;
+  if (x > y) return 1;
+  return 0;
+}
+
+int lfdcmp(const void *a, const void *b) {
+  unsigned int ta = *((unsigned int *) a);
+  unsigned int tb = *((unsigned int *) b);
+                  /* Isn't C a wonderful language? */
+  switch (sorting_mode) {
+    case REVDFWDT: if (DAYOF(ta) == DAYOF(tb)) {
+    case FORWARD :     return intcmp(ta, tb);
+                   } else {
+    case REVERSE :     return intcmp(tb, ta);
+                   }
+  }
+  return 0;
+}
+
+void testpigeon(int mode)
+{
+  unsigned int data[6] = {
+    10001, 10004, 20022, 20002, 30008, 30007
+  };
+  sorting_mode = mode;
+  qsort(data, 6, sizeof(unsigned int), lfdcmp);
+  for (int i = 0; i < 6; i++) printf("%5u ", data[i]);
+  printf("\n");
+}
+
+/* Delicate cases: unstructured switch containing
+     early break
+     loop w/ break
+     regular switch
+*/
+
+void torture(int a, int b)
+{
+  switch(a) {
+    L1: printf("L1 "); /*fallthrough*/
+    L2: printf("L2 "); break;
+    case 0:
+      printf("0 "); /*fallthrough*/
+    case 1:
+      printf("1 "); break;
+    case 2:
+      printf("2 "); goto L1;
+    case 3:
+    L3:
+      printf("3 "); goto L2;
+    case 4:
+      printf("4 "); goto L3;
+    case 5:
+      while (1) { printf("5"); b--; if (b <= 0) { printf(" "); break; }};
+      break;
+    case 6:
+      switch (b) {
+        case 1: printf("60"); break;
+        case 2: printf("61"); break;
+        default: printf("6X");
+      }
+      printf("Y ");
+      break;
+    default:
+      printf("? ");
+  }
+}
+
+int main()
+{
+  char dest[16];
+  send(dest, "0123456789AB", 13);
+  printf("%s\n", dest);
+
+  quotestring("(ab$cd)", 0); putchar('\n');
+  quotestring("(ab$cd)", 1); putchar('\n');
+
+  char c;
+  while ((c = decompressor()) != EOF) putchar(c);
+
+  testpigeon(FORWARD);
+  testpigeon(REVERSE);
+  testpigeon(REVDFWDT);
+
+  torture(0, 0); torture(1, 0); torture(2, 0); torture(3, 0); torture(4, 0);
+  printf("\n");
+  for (int b = 1; b <= 3; b++) torture(5, b);
+  printf("\n");
+  for (int b = 1; b <= 3; b++) torture(6, b);
+  printf("\n");
+
+  return 0;
+}
-- 
cgit