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2017-10-13 Jakub Jelinek <jakub@redhat.com>
PR target/82274
* libgcc2.c (__mulvDI3): If both operands have
the same highpart of -1 and the topmost bit of lowpart is 0,
multiplication overflows even if both lowparts are 0.
* gcc.dg/pr82274-1.c: New test.
--- libgcc/libgcc2.c 2017/10/13 16:50:13 253733
+++ libgcc/libgcc2.c 2017/10/13 17:19:12 253734
@@ -375,7 +375,8 @@
}
else
{
- if (uu.s.high == (Wtype) -1 && vv.s.high == (Wtype) - 1)
+ if ((uu.s.high & vv.s.high) == (Wtype) -1
+ && (uu.s.low | vv.s.low) != 0)
{
DWunion ww = {.ll = (UDWtype) (UWtype) uu.s.low
* (UDWtype) (UWtype) vv.s.low};
--- /dev/null
+++ gcc/testsuite/gcc.dg/pr82274-1.c
@@ -0,0 +1,16 @@
+/* PR target/82274 */
+/* { dg-do run } */
+/* { dg-shouldfail "trapv" } */
+/* { dg-options "-ftrapv" } */
+
+int
+main ()
+{
+#ifdef __SIZEOF_INT128__
+ volatile __int128 m = -(((__int128) 1) << (__CHAR_BIT__ * __SIZEOF_INT128__ / 2));
+#else
+ volatile long long m = -(1LL << (__CHAR_BIT__ * __SIZEOF_LONG_LONG__ / 2));
+#endif
+ m = m * m;
+ return 0;
+}