x86: Disable jump tables when retpolines are used (PR target/86952).

2019-03-08  Martin Liska  <mliska@suse.cz>

	PR target/86952
	* config/i386/i386.c (ix86_option_override_internal): Disable
	jump tables when retpolines are used.
2019-03-08  Martin Liska  <mliska@suse.cz>

	PR target/86952
	* gcc.target/i386/pr86952.c: New test.
	* gcc.target/i386/indirect-thunk-7.c: Use jump tables to match
	scanned pattern.
	* gcc.target/i386/indirect-thunk-inline-7.c: Likewise.

From-SVN: r269492

gcc/ChangeLog

+2019-03-08  Martin Liska  <mliska@suse.cz>
+
+	PR target/86952
+	* config/i386/i386.c (ix86_option_override_internal): Disable
+	jump tables when retpolines are used.
+
 2019-03-08  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR go/63560

gcc/config/i386/i386.c

@@ -4894,6 +4894,12 @@ ix86_option_override_internal (bool main_args_p,
 			   opts->x_param_values,
 			   opts_set->x_param_values);
 
+  /* PR86952: jump table usage with retpolines is slow.
+     The PR provides some numbers about the slowness.  */
+  if (ix86_indirect_branch != indirect_branch_keep
+      && !opts_set->x_flag_jump_tables)
+    opts->x_flag_jump_tables = 0;
+
   return true;
 }
 

gcc/testsuite/ChangeLog

+2019-03-08  Martin Liska  <mliska@suse.cz>
+
+	PR target/86952
+	* gcc.target/i386/pr86952.c: New test.
+	* gcc.target/i386/indirect-thunk-7.c: Use jump tables to match
+	scanned pattern.
+	* gcc.target/i386/indirect-thunk-inline-7.c: Likewise.
+
 2019-03-08  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/89585

gcc/testsuite/gcc.target/i386/indirect-thunk-7.c

 /* { dg-do compile } */
-/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk -fno-pic" } */
+/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk -fno-pic -fjump-tables" } */
 
 void func0 (void);
 void func1 (void);

gcc/testsuite/gcc.target/i386/indirect-thunk-inline-7.c

 /* { dg-do compile } */
-/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk-inline -fno-pic" } */
+/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk-inline -fno-pic -fjump-tables" } */
 
 void func0 (void);
 void func1 (void);

gcc/testsuite/gcc.target/i386/pr86952.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -mindirect-branch=thunk -fdump-tree-switchlower1" } */
+
+int global;
+
+int 
+foo (int x)
+{
+  switch (x & 7)
+    {
+      case 0: ; return 1722;
+      case 1: global += 1; return 1060;
+      case 2: ; return 1990;
+      case 3: ; return 1242;
+      case 4: ; return 1466;
+      case 5: ; return 894;
+      case 6: ; return 570;
+      case 7: ; return 572;
+      default: return 0;
+    }
+}
+
+/* { dg-final { scan-tree-dump ";; GIMPLE switch case clusters: 1 2 3 4 5 6 7" "switchlower1" } } */