ifcvt: Punt if not onlyjump_p for find_if_case_{1,2} [PR104814]

find_if_case_{1,2} implicitly assumes conditional jumps and rewrites them,
so if they have extra side-effects or are say asm goto, things don't work
well, either the side-effects are lost or we could ICE.
In particular, the testcase below on s390x has there a doloop instruction
that decrements a register in addition to testing it for non-zero and
conditionally jumping based on that.

The following patch fixes that by punting for !onlyjump_p case, i.e.
if there are side-effects in the jump instruction or it isn't a plain PC
setter.

Also, it assumes BB_END (test_bb) will be always non-NULL, because basic
blocks with 2 non-abnormal successor edges should always have some instruction
at the end that determines which edge to take.

2022-03-15  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/104814
	* ifcvt.cc (find_if_case_1, find_if_case_2): Punt if test_bb doesn't
	end with onlyjump_p.  Assume BB_END (test_bb) is always non-NULL.

	* gcc.c-torture/execute/pr104814.c: New test.

2 files changed, 40 insertions, 4 deletions

diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
index 6305621..22960a6 100644
--- a/gcc/ifcvt.cc
+++ b/gcc/ifcvt.cc
@@ -5251,14 +5251,17 @@ find_if_case_1 (basic_block test_bb, edge then_edge, edge else_edge)
   if ((BB_END (then_bb)
        && JUMP_P (BB_END (then_bb))
        && CROSSING_JUMP_P (BB_END (then_bb)))
-      || (BB_END (test_bb)
-	  && JUMP_P (BB_END (test_bb))
+      || (JUMP_P (BB_END (test_bb))
 	  && CROSSING_JUMP_P (BB_END (test_bb)))
       || (BB_END (else_bb)
 	  && JUMP_P (BB_END (else_bb))
 	  && CROSSING_JUMP_P (BB_END (else_bb))))
     return FALSE;
 
+  /* Verify test_bb ends in a conditional jump with no other side-effects.  */
+  if (!onlyjump_p (BB_END (test_bb)))
+    return FALSE;
+
   /* THEN has one successor.  */
   if (!single_succ_p (then_bb))
     return FALSE;
@@ -5372,14 +5375,17 @@ find_if_case_2 (basic_block test_bb, edge then_edge, edge else_edge)
   if ((BB_END (then_bb)
        && JUMP_P (BB_END (then_bb))
        && CROSSING_JUMP_P (BB_END (then_bb)))
-      || (BB_END (test_bb)
-	  && JUMP_P (BB_END (test_bb))
+      || (JUMP_P (BB_END (test_bb))
 	  && CROSSING_JUMP_P (BB_END (test_bb)))
       || (BB_END (else_bb)
 	  && JUMP_P (BB_END (else_bb))
 	  && CROSSING_JUMP_P (BB_END (else_bb))))
     return FALSE;
 
+  /* Verify test_bb ends in a conditional jump with no other side-effects.  */
+  if (!onlyjump_p (BB_END (test_bb)))
+    return FALSE;
+
   /* ELSE has one successor.  */
   if (!single_succ_p (else_bb))
     return FALSE;
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr104814.c b/gcc/testsuite/gcc.c-torture/execute/pr104814.c
new file mode 100644
index 0000000..7d4f8ab
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr104814.c
@@ -0,0 +1,30 @@
+/* PR rtl-optimization/104814 */
+
+short a = 0;
+static long b = 0;
+int c = 7;
+char d = 0;
+short *e = &a;
+long f = 0;
+
+unsigned long
+foo (unsigned long h, long j)
+{
+  return j == 0 ? h : h / j;
+}
+
+int
+main ()
+{
+  long k = f;
+  for (; c; --c)
+    {
+      for (int i = 0; i < 7; ++i)
+	;
+      long m = foo (f, --b);
+      d = ((char) m | *e) <= 43165;
+    }
+  if (b != -7)
+    __builtin_abort ();
+  return 0;
+}