From b8c4171ebd72079e55aceadbcfc883f517cdf895 Mon Sep 17 00:00:00 2001
From: Alexandre Oliva <oliva@adacore.com>
Date: Thu, 24 Mar 2022 10:02:27 -0300
Subject: [PATCH] hardcmp: split before dispatch edge

If we harden a compare at the end of a block with an edge to the
abnormal dispatch block, it won't have a single successor.  Arrange to
split the block at its final stmt so as to have a single succ.


for  gcc/ChangeLog

	PR middle-end/104975
	* gimple-harden-conditionals.cc
	(pass_harden_compares::execute): Force split in case of
	multiple edges.

for  gcc/testsuite/ChangeLog

	PR middle-end/104975
	* gcc.dg/pr104975.c: New.
---
 gcc/gimple-harden-conditionals.cc | 12 +++++++++---
 gcc/testsuite/gcc.dg/pr104975.c   | 20 ++++++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr104975.c

diff --git a/gcc/gimple-harden-conditionals.cc b/gcc/gimple-harden-conditionals.cc
index 6a5fc3f..be01f3e 100644
--- a/gcc/gimple-harden-conditionals.cc
+++ b/gcc/gimple-harden-conditionals.cc
@@ -509,10 +509,16 @@ pass_harden_compares::execute (function *fun)
 	gsi_insert_before (&gsi_split, asgnck, GSI_SAME_STMT);
 
 	/* We wish to insert a cond_expr after the compare, so arrange
-	   for it to be at the end of a block if it isn't.  */
-	if (!gsi_end_p (gsi_split))
+	   for it to be at the end of a block if it isn't, and for it
+	   to have a single successor in case there's more than
+	   one, as in PR104975.  */
+	if (!gsi_end_p (gsi_split)
+	    || !single_succ_p (gsi_bb (gsi_split)))
 	  {
-	    gsi_prev (&gsi_split);
+	    if (!gsi_end_p (gsi_split))
+	      gsi_prev (&gsi_split);
+	    else
+	      gsi_split = gsi_last_bb (gsi_bb (gsi_split));
 	    basic_block obb = gsi_bb (gsi_split);
 	    basic_block nbb = split_block (obb, gsi_stmt (gsi_split))->dest;
 	    gsi_next (&gsi_split);
diff --git a/gcc/testsuite/gcc.dg/pr104975.c b/gcc/testsuite/gcc.dg/pr104975.c
new file mode 100644
index 0000000..04532fc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr104975.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -fharden-compares -fno-inline -fno-ipa-pure-const" } */
+
+__attribute__ ((pure, returns_twice)) int
+bar (int);
+
+int
+quux (void)
+{
+  return 0;
+}
+
+int
+foo (short int x)
+{
+  x = !x;
+  bar (quux ());
+
+  return x;
+}
-- 
2.7.4