From: Jakub Jelinek <jakub@redhat.com>
Date: Thu, 9 Oct 2025 16:06:39 +0000 (+0200)
Subject: gimplify: Fix up side-effect handling in 2nd __builtin_c[lt]zg argument [PR122188]
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=363edb309df35b0f4d9a4eb21288fae64d021648;p=thirdparty%2Fgcc.git

gimplify: Fix up side-effect handling in 2nd __builtin_c[lt]zg argument [PR122188]

The patch from yesterday made me think about side-effects in the second
argument of __builtin_c[lt]zg.  When we change
__builtin_c[lt]zg (x, y)
when y is not INTEGER_CST into
x ? __builtin_c[lt]zg (x) : y
with evaluating x only once, we omit the side-effects in y unless x is not
0.  That looks undesirable, we should evaluate side-effects in y
unconditionally.

2025-10-09  Jakub Jelinek  <jakub@redhat.com>

	PR c/122188
	* c-gimplify.cc (c_gimplify_expr): Also gimplify the second operand
	before the COND_EXPR and use in COND_EXPR result of gimplification.

	* gcc.dg/torture/pr122188.c: New test.

(cherry picked from commit 579de8f5295b05573d05f6e4102f1428f35c9f17)
---

diff --git a/gcc/c-family/c-gimplify.cc b/gcc/c-family/c-gimplify.cc
index 0aad93e618c..8fbf6e49509 100644
--- a/gcc/c-family/c-gimplify.cc
+++ b/gcc/c-family/c-gimplify.cc
@@ -1013,6 +1013,10 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED,
 	    if (gimplify_expr (&a, pre_p, post_p, is_gimple_val, fb_rvalue)
 		== GS_ERROR)
 	      return GS_ERROR;
+	    tree b = CALL_EXPR_ARG (*expr_p, 1);
+	    if (gimplify_expr (&b, pre_p, post_p, is_gimple_val, fb_rvalue)
+		== GS_ERROR)
+	      return GS_ERROR;
 	    tree c = build_call_expr_loc (EXPR_LOCATION (*expr_p),
 					  fndecl, 1, a);
 	    *expr_p = build3_loc (EXPR_LOCATION (*expr_p), COND_EXPR,
@@ -1020,7 +1024,7 @@ c_gimplify_expr (tree *expr_p, gimple_seq *pre_p ATTRIBUTE_UNUSED,
 				  build2_loc (EXPR_LOCATION (*expr_p),
 					      NE_EXPR, boolean_type_node, a,
 					      build_zero_cst (TREE_TYPE (a))),
-				  c, CALL_EXPR_ARG (*expr_p, 1));
+				  c, b);
 	    return GS_OK;
 	  }
 	break;
diff --git a/gcc/testsuite/gcc.dg/torture/pr122188.c b/gcc/testsuite/gcc.dg/torture/pr122188.c
new file mode 100644
index 00000000000..2c549630f9d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr122188.c
@@ -0,0 +1,33 @@
+/* PR c/122188 */
+/* { dg-do run } */
+
+int
+foo (unsigned x, int y)
+{
+  unsigned a = x;
+  int b = y;
+  int ret = __builtin_ctzg (x++, y++);
+  if (x != a + 1 || y != b + 1)
+    __builtin_abort ();
+  return ret;
+}
+
+int
+bar (unsigned x, int y)
+{
+  unsigned a = x;
+  int b = y;
+  int ret = __builtin_clzg (x++, y++);
+  if (x != a + 1 || y != b + 1)
+    __builtin_abort ();
+  return ret;
+}
+
+int
+main ()
+{
+  if (foo (0, 42) != 42 || foo (1, 5) != 0 || foo (4, 17) != 2)
+    __builtin_abort ();
+  if (bar (0, 42) != 42 || bar (~0U, 5) != 0 || bar (~0U >> 4, 17) != 4)
+    __builtin_abort ();
+}