--- gcc/testsuite/c-c++-common/Wduplicated-branches-1.c
+++ gcc/testsuite/c-c++-common/Wduplicated-branches-1.c
@@ -0,0 +1,187 @@
+/* PR c/64279 */
+/* { dg-do compile } */
+/* { dg-options "-Wduplicated-branches -O2" } */
+
+extern void foo (int);
+extern int g;
+extern int a[10];
+
+int
+f (int i, int *p)
+{
+ const int j = 0;
+ if (j == 0)
+ {
+ if (i > 10) /* { dg-warning "this condition has identical branches" } */
+ /* Optimizers can figure out that this is 1. */
+ *p = j * 2 + 1;
+ else
+ *p = 1;
+ }
I wonder if this test case (perhaps with a slight modification)
illustrates the concern Jeff raised. Suppose j is an argument
to the function whose value of zero is determined by constant
propagation. Such code is not uncommon but will presumably be
diagnosed, which in all likelihood will be considered a false
positive. I don't have a sense of how pervasive such cases
might be. Do you have any data from projects other than GCC?
(Since there are no fixes in the patch I assume it didn't find
any bugs in GCC itself.)
Martin
