From: Stefan Schulze Frielinghaus <[email protected]>
On s390 bit-fields are layed out from left-to-right. Therefore, struct
member c starts 7+2+6+3 bits from the left aka the most significant bit.
The assignment to f.e only writes a single byte but the struct member c
crosses two bytes. Using index 3 and assigning 7 to f.e results in only
writing a single bit of f.bf.c which is set to 0 which means the whole
member stays 0. A probably more interesting index is 2 which renders
f.bf.c equal to 14 in the end.
gcc/testsuite/ChangeLog:
* gcc.dg/torture/pr126650.c: Fix index and expected value for
s390 where bit fields are layed out from left-to-right.
---
Tested on s390x-linux and x86_64-linux.
gcc/testsuite/gcc.dg/torture/pr126650.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/gcc/testsuite/gcc.dg/torture/pr126650.c
b/gcc/testsuite/gcc.dg/torture/pr126650.c
index 166705d9cfe..f9997b16f2b 100644
--- a/gcc/testsuite/gcc.dg/torture/pr126650.c
+++ b/gcc/testsuite/gcc.dg/torture/pr126650.c
@@ -1,5 +1,13 @@
/* { dg-do run } */
+#if __s390__
+# define IDX 2
+# define VAL 14
+#else
+# define IDX 3
+# define VAL -64
+#endif
+
#include <stdarg.h>
#include <stdlib.h>
@@ -10,7 +18,7 @@ void __attribute__((noipa)) foo (int n, ...)
va_list list;
va_start (list, n);
int val = va_arg (list, int);
- if (val != -64)
+ if (val != VAL)
abort ();
va_end (list);
}
@@ -30,6 +38,6 @@ int main()
char e[4];
} f;
f.d = a;
- f.e[3] = 7;
+ f.e[IDX] = 7;
foo (1, f.bf.c);
}
--
2.54.0
