[gcc(refs/users/marxin/heads/PR98182-fix-negative-if-to-switch)] if-to-switch: fix matching of negative conditions

[Martin Liska <marxin@gcc.gnu.org>]

https://gcc.gnu.org/g:47bcd6df91cfcfced75ef1289841eb5626a6d6cb

commit 47bcd6df91cfcfced75ef1289841eb5626a6d6cb
Author: Martin Liska <mliska@suse.cz>
Date:   Tue Dec 8 13:18:37 2020 +0100

    if-to-switch: fix matching of negative conditions
    
    gcc/ChangeLog:
    
            PR tree-optimization/98182
            * gimple-if-to-switch.cc (pass_if_to_switch::execute): Request
            chain linkage through false edges only.
    
    gcc/testsuite/ChangeLog:
    
            PR tree-optimization/98182
            * gcc.dg/tree-ssa/if-to-switch-10.c: New test.
            * gcc.dg/tree-ssa/pr98182.c: New test.

Diff:
---
 gcc/gimple-if-to-switch.cc                      |  6 ++++
 gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c | 44 +++++++++++++++++++++++++
 gcc/testsuite/gcc.dg/tree-ssa/pr98182.c         | 18 ++++++++++
 3 files changed, 68 insertions(+)

diff --git a/gcc/gimple-if-to-switch.cc b/gcc/gimple-if-to-switch.cc
index 8e1043ae7c4..311f6f6ac97 100644
--- a/gcc/gimple-if-to-switch.cc
+++ b/gcc/gimple-if-to-switch.cc
@@ -522,6 +522,12 @@ pass_if_to_switch::execute (function *fun)
 	      if (!info2 || info->m_ranges[0].exp != info2->m_ranges[0].exp)
 		break;
 
+	      /* It is important that the blocks are linked through FALSE_EDGE.
+		 For an expression of index != VALUE, true and false edges
+		 are flipped.  */
+	      if (info2->m_false_edge != e)
+		break;
+
 	      chain->m_entries.safe_push (info2);
 	      bitmap_set_bit (seen_bbs, e->src->index);
 	      info = info2;
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c b/gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c
new file mode 100644
index 00000000000..7b8da1c9f3c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/if-to-switch-10.c
@@ -0,0 +1,44 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-iftoswitch-optimized" } */
+
+int global;
+int foo ();
+
+int main(int argc, char **argv)
+{
+  if (argc != 1)
+    {
+      if (argc != 2)
+	{
+	  if (argc == 3)
+	    {
+	      foo ();
+	      foo ();
+	    }
+	  else if (argc == 4)
+	    {
+	      foo ();
+	    }
+	  else if (argc == 5)
+	    {
+	      global = 2;
+	    }
+	  else
+	    global -= 123;
+	}
+      else
+	{
+	  global += 1;
+	}
+    }
+  else
+    foo ();
+
+  
+  global -= 12;
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump "Canonical GIMPLE case clusters: 1 2 3 4 5" "iftoswitch" } } */
+/* { dg-final { scan-tree-dump "Condition chain with \[^\n\r]\* BBs transformed into a switch statement." "iftoswitch" } } */
+
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr98182.c b/gcc/testsuite/gcc.dg/tree-ssa/pr98182.c
new file mode 100644
index 00000000000..29a547e3788
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr98182.c
@@ -0,0 +1,18 @@
+/* PR tree-optimization/98182 */
+/* { dg-do compile } */
+/* { dg-options "-O1 --param case-values-threshold=1 -fdump-tree-iftoswitch-optimized" } */
+
+int global;
+int foo ();
+
+int main(int argc, char **argv)
+{
+  if (argc != 1)
+    __builtin_abort ();
+  else if (argc != 2)
+    __builtin_abort ();
+  else
+    return 0;
+}
+
+/* { dg-final { scan-tree-dump-not "Condition chain" "iftoswitch" } } */