Enable jump threading at -O1.

My previous patch gating all jump threading by -fthread-jumps had the
side effect of turning off DOM jump threading at -O1.  This causes
numerous -Wuninitialized false positives.  This patch turns on jump
threading at -O1 to minimize the disruption.

gcc/ChangeLog:

	* cfgcleanup.c (pass_jump::execute): Check
	flag_expensive_optimizations.
	(pass_jump_after_combine::gate): Same.
	* doc/invoke.texi (-fthread-jumps): Enable for -O1.
	* opts.c (default_options_table): Enable -fthread-jumps at -O1.
	* tree-ssa-threadupdate.c
	(fwd_jt_path_registry::remove_jump_threads_including): Bail unless
	flag_thread_jumps.

gcc/testsuite/ChangeLog:

	* gcc.dg/auto-init-uninit-1.c: Adjust.
	* gcc.dg/auto-init-uninit-15.c: Same.
	* gcc.dg/guality/example.c: Same.
	* gcc.dg/loop-8.c: Same.
	* gcc.dg/strlenopt-40.c: Same.
	* gcc.dg/tree-ssa/pr18133-2.c: Same.
	* gcc.dg/tree-ssa/pr18134.c: Same.
	* gcc.dg/uninit-1.c: Same.
	* gcc.dg/uninit-pr44547.c: Same.
	* gcc.dg/uninit-pr59970.c: Same.

gcc/cfgcleanup.c

@@ -3239,7 +3239,8 @@ pass_jump::execute (function *)
   if (dump_file)
     dump_flow_info (dump_file, dump_flags);
   cleanup_cfg ((optimize ? CLEANUP_EXPENSIVE : 0)
-	       | (flag_thread_jumps ? CLEANUP_THREADING : 0));
+	       | (flag_thread_jumps && flag_expensive_optimizations
+		  ? CLEANUP_THREADING : 0));
   return 0;
 }
 
@@ -3274,7 +3275,10 @@ public:
   {}
 
   /* opt_pass methods: */
-  virtual bool gate (function *) { return flag_thread_jumps; }
+  virtual bool gate (function *)
+  {
+    return flag_thread_jumps && flag_expensive_optimizations;
+  }
   virtual unsigned int execute (function *);
 
 }; // class pass_jump_after_combine

gcc/doc/invoke.texi

@@ -10781,7 +10781,7 @@ so, the first branch is redirected to either the destination of the
 second branch or a point immediately following it, depending on whether
 the condition is known to be true or false.
 
-Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}.
+Enabled at levels @option{-O1}, @option{-O2}, @option{-O3}, @option{-Os}.
 
 @item -fsplit-wide-types
 @opindex fsplit-wide-types

gcc/opts.c

@@ -569,6 +569,7 @@ static const struct default_options default_options_table[] =
     { OPT_LEVELS_1_PLUS, OPT_freorder_blocks, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_fshrink_wrap, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_fsplit_wide_types, NULL, 1 },
+    { OPT_LEVELS_1_PLUS, OPT_fthread_jumps, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_ftree_builtin_call_dce, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_ftree_ccp, NULL, 1 },
     { OPT_LEVELS_1_PLUS, OPT_ftree_ch, NULL, 1 },
@@ -629,7 +630,6 @@ static const struct default_options default_options_table[] =
 #endif
     { OPT_LEVELS_2_PLUS, OPT_fstrict_aliasing, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_fstore_merging, NULL, 1 },
-    { OPT_LEVELS_2_PLUS, OPT_fthread_jumps, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_ftree_pre, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_ftree_switch_conversion, NULL, 1 },
     { OPT_LEVELS_2_PLUS, OPT_ftree_tail_merge, NULL, 1 },

gcc/testsuite/gcc.dg/auto-init-uninit-1.c

@@ -1,5 +1,5 @@
 /* Spurious uninitialized variable warnings, case 1.
    Taken from cppfiles.c (merge_include_chains) */
 /* { dg-do compile } */
-/* { dg-options "-O -Wuninitialized -fthread-jumps -ftrivial-auto-var-init=zero" } */
+/* { dg-options "-O -Wuninitialized -ftrivial-auto-var-init=zero" } */
 #include "uninit-1.c"

gcc/testsuite/gcc.dg/auto-init-uninit-15.c

@@ -5,7 +5,7 @@
    But it is of course ok if we warn in bar about uninitialized use
    of j.  (not xfailed alternative)  */
 /* { dg-do compile } */
-/* { dg-options "-O1 -Wuninitialized -fthread-jumps -ftrivial-auto-var-init=zero" } */
+/* { dg-options "-O1 -Wuninitialized -ftrivial-auto-var-init=zero" } */
 
 inline int
 foo (int i)

gcc/testsuite/gcc.dg/guality/example.c

@@ -1,4 +1,5 @@
 /* { dg-options "-g" } */
+/* { dg-do run { xfail { ! aarch64*-*-* } } } */
 /* { dg-xfail-run-if "" aarch64*-*-* "*" { "-O[01g]" } } */
 
 #define GUALITY_DONT_FORCE_LIVE_AFTER -1

gcc/testsuite/gcc.dg/loop-8.c

@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-O1 -fthread-jumps -fdump-rtl-loop2_invariant" } */
+/* { dg-options "-O1 -fdump-rtl-loop2_invariant" } */
 /* { dg-skip-if "unexpected IV" { "hppa*-*-* mips*-*-* visium-*-* powerpc*-*-* riscv*-*-* mmix-*-* vax-*-*" } } */
 /* Load immediate on condition is available from z13 on and prevents moving
    the load out of the loop, so always run this test with -march=zEC12 that

gcc/testsuite/gcc.dg/strlenopt-40.c

@@ -1,7 +1,7 @@
 /* PR tree-optimization/83671 - fix for false positive reported by
    -Wstringop-overflow does not work with inlining
    { dg-do compile }
-   { dg-options "-O1 -fthread-jumps -fdump-tree-optimized" } */
+   { dg-options "-O1 -fdump-tree-optimized" } */
 
 #include "strlenopt.h"
 

gcc/testsuite/gcc.dg/tree-ssa/pr18133-2.c

@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-O1 -fthread-jumps -fdump-tree-optimized-blocks" } */
+/* { dg-options "-O1 -fdump-tree-optimized-blocks" } */
 
 int c, d;
 

gcc/testsuite/gcc.dg/tree-ssa/pr18134.c

@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-O1 -fthread-jumps -fdump-tree-optimized" } */
+/* { dg-options "-O1 -fdump-tree-optimized" } */
 
 int  foo (int a)
 {

gcc/testsuite/gcc.dg/uninit-1.c

@@ -1,7 +1,7 @@
 /* Spurious uninitialized variable warnings, case 1.
    Taken from cppfiles.c (merge_include_chains) */
 /* { dg-do compile } */
-/* { dg-options "-O -Wuninitialized -fthread-jumps" } */
+/* { dg-options "-O -Wuninitialized" } */
 
 struct list
 {

gcc/testsuite/gcc.dg/uninit-pr44547.c

@@ -1,7 +1,7 @@
 /* PR tree-optimization/44547 - -Wuninitialized reports false warning
    in nested switch statements
    { dg-do compile }
-   { dg-options "-O1 -Wall -fthread-jumps" } */
+   { dg-options "-O1 -Wall" } */
 
 __attribute__ ((noipa)) int test_O1 (int argc)
 {

gcc/testsuite/gcc.dg/uninit-pr59970.c

@@ -41,7 +41,7 @@ d_demangle_callback_O1 (const char *mangled)
 #pragma GCC pop_options
 
 
-#pragma GCC optimize ("Og,thread-jumps")
+#pragma GCC optimize ("Og")
 
 __attribute__ ((noipa)) int
 d_demangle_callback_Og (const char *mangled)

gcc/tree-ssa-threadupdate.c

@@ -2570,7 +2570,7 @@ valid_jump_thread_path (vec<jump_thread_edge *> *path)
 void
 fwd_jt_path_registry::remove_jump_threads_including (edge_def *e)
 {
-  if (!m_paths.exists ())
+  if (!m_paths.exists () || !flag_thread_jumps)
     return;
 
   edge *slot = m_removed_edges->find_slot (e, INSERT);