[PATCH] ifcvt, v2: Punt if not onlyjump_p for find_if_case_{1,2} [PR104814]

Jakub Jelinek jakub@redhat.com
Mon Mar 14 10:24:32 GMT 2022


On Sun, Mar 13, 2022 at 02:43:18PM +0100, Jakub Jelinek via Gcc-patches wrote:
> > Are the !BB_END tests really necessary?  cond_exec_process_if_block has the 
> > same test on onlyjump_p without it.  Likewise for noce_find_if_block.
> 
> Probably not, I've put it there only because the neighboring code is testing
> it too:
>   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))
>           && 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;
> find_if_header which calls find_if_case_* has:
>   if (EDGE_COUNT (test_bb->succs) != 2)
>     return NULL;
> at the start, and I think an empty bb can't have more than one successor,
> because there is nothing to cause different control flow.

Here is an updated patch for it.  Ok for trunk?

2022-03-14  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.

--- gcc/ifcvt.cc.jj	2022-03-14 10:34:16.350172371 +0100
+++ gcc/ifcvt.cc	2022-03-14 11:20:32.425384101 +0100
@@ -5251,14 +5251,17 @@ find_if_case_1 (basic_block test_bb, edg
   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, edg
   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;
--- gcc/testsuite/gcc.c-torture/execute/pr104814.c.jj	2022-03-14 11:18:57.188717248 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr104814.c	2022-03-14 11:18:57.188717248 +0100
@@ -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;
+}


	Jakub



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