[PATCH] builtins: Fix fold_builtin_query clzg/ctzg side-effects handling [PR112639]

[Jakub Jelinek <jakub@redhat.com>]

Hi!

As the testcase shows, I've missed one spot where initially the code thinks
it could use 2 argument IFN_CLZ/IFN_CTZ form, but then verifies it can't
because it doesn't have the right target value and turns it into the
arg0 ? arg1 : .C[LT]Z (arg0)
form.  That form evaluates the argument twice though and so needs save_expr,
which I've missed to call in that case.  In other cases where it is known
from the beginning that it will be needed (e.g. the __builtin_clzg case
on types smaller than unsigned int where we'll need to add an addend
to the clz value) or the unsigned __int128 expansion called save_expr
before.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2023-11-21  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/112639
	* builtins.cc (fold_builtin_bit_query): If arg0 has side-effects, arg1
	is specified but cleared, call save_expr on arg0.

	* gcc.dg/torture/pr112639.c: New test.

--- gcc/builtins.cc.jj	2023-11-20 10:36:18.642625716 +0100
+++ gcc/builtins.cc	2023-11-20 15:25:59.665718971 +0100
@@ -9819,6 +9819,8 @@ fold_builtin_bit_query (location_t loc,
 	  if (!direct_internal_fn_supported_p (ifn, arg0_type,
 					       OPTIMIZE_FOR_BOTH))
 	    arg2 = NULL_TREE;
+	  if (arg2 == NULL_TREE)
+	    arg0 = save_expr (arg0);
 	}
       if (fcodei == END_BUILTINS || arg2)
 	call = build_call_expr_internal_loc (loc, ifn, integer_type_node,
--- gcc/testsuite/gcc.dg/torture/pr112639.c.jj	2023-11-20 15:32:24.994391656 +0100
+++ gcc/testsuite/gcc.dg/torture/pr112639.c	2023-11-20 15:34:14.395882993 +0100
@@ -0,0 +1,34 @@
+/* PR middle-end/112639 */
+/* { dg-do run } */
+
+unsigned long long b = 0;
+
+int
+foo (void)
+{
+  return __builtin_clzg (b++, __SIZEOF_LONG_LONG__ * __CHAR_BIT__);
+}
+
+int
+bar (void)
+{
+  return __builtin_ctzg (b++, __SIZEOF_LONG_LONG__ * __CHAR_BIT__);
+}
+
+int
+main ()
+{
+  if (foo () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ || b != 1)
+    __builtin_abort ();
+  if (foo () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ - 1 || b != 2)
+    __builtin_abort ();
+  if (foo () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ - 2 || b != 3)
+    __builtin_abort ();
+  b = 0;
+  if (bar () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ || b != 1)
+    __builtin_abort ();
+  if (bar () != 0 || b != 2)
+    __builtin_abort ();
+  if (bar () != 1 || b != 3)
+    __builtin_abort ();
+}

	Jakub