re PR tree-optimization/69196 (code size regression with jump threading at -O2)

	PR tree-optimization/69196
	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
	Appropriately clamp the number of statements to copy when the
	thread path does not traverse a loop backedge.

	PR tree-optimization/69196
	* gcc.dg/tree-ssa/pr69196.c: New test.

From-SVN: r233870

4 files changed, 166 insertions, 0 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 982a7c0..88f0806 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -8,6 +8,11 @@
 
 	PR tree-optimization/69196
 	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
+	Appropriately clamp the number of statements to copy when the
+	thread path does not traverse a loop backedge.
+
+	PR tree-optimization/69196
+	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
 	Do count some PHIs in the thread path against the insn count.  Decrease
 	final statement count by one as the control statement in the last
 	block will get removed.  Remove special cased code for handling PHIs		in the last block.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index bdc4b11..1e6a850 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -5,6 +5,9 @@
 2016-03-01  Jeff Law  <law@redhat.com>
 
 	PR tree-optimization/69196
+	* gcc.dg/tree-ssa/pr69196.c: New test.
+
+	PR tree-optimization/69196
 	* gcc.dg/tree-ssa/vrp46.c: Twiddle threading params to keep it from
 	duplicating code and spoiling the expected output.
 
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr69196-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr69196-1.c
new file mode 100644
index 0000000..11c7cf5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr69196-1.c
@@ -0,0 +1,138 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp1-details" } */
+
+/* { dg-final { scan-tree-dump "FSM did not thread around loop and would copy too many statements" "vrp1" } } */
+
+
+typedef __builtin_va_list __gnuc_va_list;
+typedef __gnuc_va_list va_list;
+extern void rtems_putc(char c);
+
+void vprintk(
+  const char *fmt,
+  va_list ap
+)
+{
+  for (; *fmt != '\0'; fmt++) {
+    unsigned base = 0;
+    unsigned width = 0;
+    enum {
+      LFLAG_INT,
+      LFLAG_LONG,
+      LFLAG_LONG_LONG
+    } lflag = LFLAG_INT;
+    _Bool minus = 0;
+    _Bool sign = 0;
+    char lead = ' ';
+    char c = *fmt;
+    long long num;
+
+    if (c != '%') {
+      rtems_putc(c);
+      continue;
+    }
+
+    ++fmt; c = *fmt;
+
+    if (c == '0') {
+      lead = '0';
+      ++fmt; c = *fmt;
+    }
+
+    if (c == '-') {
+      minus = 1;
+      ++fmt; c = *fmt;
+    }
+
+    while (c >= '0' && c <= '9' ) {
+      width *= 10;
+      width += ((unsigned) c - '0');
+      ++fmt; c = *fmt;
+    }
+
+    if (c == 'l') {
+      lflag = LFLAG_LONG;
+      ++fmt; c = *fmt;
+
+      if (c == 'l') {
+        lflag = LFLAG_LONG_LONG;
+        ++fmt; c = *fmt;
+      }
+    }
+
+    if ( c == 'c' ) {
+
+      char chr = (char) __builtin_va_arg(ap,int);
+      rtems_putc(chr);
+      continue;
+    }
+
+    if ( c == 's' ) {
+      unsigned i, len;
+      char *s, *str;
+
+      str = __builtin_va_arg(ap,char *);
+
+      if ( str == ((void *)0) ) {
+        str = "";
+      }
+
+
+      for ( len=0, s=str ; *s ; len++, s++ )
+        ;
+
+
+      if ( !minus )
+        for ( i=len ; i<width ; i++ )
+          rtems_putc(' ');
+
+
+      if (width == 0) {
+          width = len;
+      }
+
+
+      for ( i=0 ; i<width && *str ; str++ )
+        rtems_putc(*str);
+
+
+      if ( minus )
+        for ( i=len ; i<width ; i++ )
+          rtems_putc(' ');
+
+      continue;
+    }
+
+
+    if ( c == 'o' || c == 'O' ) {
+      base = 8; sign = 0;
+    } else if ( c == 'i' || c == 'I' ||
+                c == 'd' || c == 'D' ) {
+      base = 10; sign = 1;
+    } else if ( c == 'u' || c == 'U' ) {
+      base = 10; sign = 0;
+    } else if ( c == 'x' || c == 'X' ) {
+      base = 16; sign = 0;
+    } else if ( c == 'p' ) {
+      base = 16; sign = 0; lflag = LFLAG_LONG;
+    } else {
+      rtems_putc(c);
+      continue;
+    }
+
+    switch (lflag) {
+      case LFLAG_LONG:
+        num = sign ? (long long) __builtin_va_arg(ap,long)
+          : (long long) __builtin_va_arg(ap,unsigned long);
+        break;
+      case LFLAG_LONG_LONG:
+        num = __builtin_va_arg(ap,long long);
+        break;
+      case LFLAG_INT:
+      default:
+        num = sign ? (long long) __builtin_va_arg(ap,int)
+          : (long long) __builtin_va_arg(ap,unsigned int);
+        break;
+    }
+  }
+}
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index 3028504..747296b 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -429,6 +429,26 @@ fsm_find_control_statement_thread_paths (tree name,
 	      continue;
 	    }
 
+
+	  /* If this path does not thread through the loop latch, then we are
+	     using the FSM threader to find old style jump threads.  This
+	     is good, except the FSM threader does not re-use an existing
+	     threading path to reduce code duplication.
+
+	     So for that case, drastically reduce the number of statements
+	     we are allowed to copy.  */
+	  if (!threaded_through_latch
+	      && (n_insns * PARAM_VALUE (PARAM_FSM_SCALE_PATH_STMTS)
+		  >= PARAM_VALUE (PARAM_MAX_JUMP_THREAD_DUPLICATION_STMTS)))
+	    {
+	      if (dump_file && (dump_flags & TDF_DETAILS))
+		fprintf (dump_file,
+			 "FSM did not thread around loop and would copy too "
+			 "many statements.\n");
+	      path->pop ();
+	      continue;
+	    }
+
 	  /* When there is a multi-way branch on the path, then threading can
 	     explode the CFG due to duplicating the edges for that multi-way
 	     branch.  So like above, only allow a multi-way branch on the path