In PR68142 you added a check for overflow + __INT_MIN__.
I can't figure out why the check for __INT_MIN__, except
that it seems specific to the test case you examined.
And indeed, this test case shows how things go wrong
with other distributed folding leading to overflow.
I added two tests, one signed, one unsigned. The second
verifies that we do still fold for the defined-overflow case.
Ok?
r~
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 9d861c6..44fe2a2 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -6116,11 +6116,9 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code,
tree wide_type,
{
tree tem = const_binop (code, fold_convert (ctype, t),
fold_convert (ctype, c));
- /* If the multiplication overflowed to INT_MIN then we lost sign
- information on it and a subsequent multiplication might
- spuriously overflow. See PR68142. */
- if (TREE_OVERFLOW (tem)
- && wi::eq_p (tem, wi::min_value (TYPE_PRECISION (ctype), SIGNED)))
+ /* If the multiplication overflowed, we lost information on it.
+ See PR68142 and PR69845. */
+ if (TREE_OVERFLOW (tem))
return NULL_TREE;
return tem;
}
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr69845-1.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr69845-1.c
new file mode 100644
index 0000000..92927ba
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr69845-1.c
@@ -0,0 +1,19 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target int32 } */
+/* { dg-options "-O -fdump-tree-gimple -fdump-tree-optimized" } */
+
+int
+main ()
+{
+ struct S { char s; } v;
+ v.s = 47;
+ int a = (int) v.s;
+ int b = (27005061 + (a + 680455));
+ int c = ((1207142401 * (((8 * b) + 9483541) - 230968044)) + 469069442);
+ if (c != 1676211843)
+ __builtin_abort ();
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "b \\\* 8" 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-not "abort" "optimized" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr69845-2.c
b/gcc/testsuite/gcc.dg/tree-ssa/pr69845-2.c
new file mode 100644
index 0000000..e0b38e9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr69845-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target int32 } */
+/* { dg-options "-O -fdump-tree-gimple -fdump-tree-optimized" } */
+
+int
+main ()
+{
+ struct S { char s; } v;
+ v.s = 47;
+ unsigned int a = (unsigned int) v.s;
+ unsigned int b = (27005061 + (a + 680455));
+ unsigned int c
+ = ((1207142401u * (((8u * b) + 9483541u) - 230968044u)) + 469069442u);
+ if (c != 1676211843u)
+ __builtin_abort ();
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "b \\\* 1067204616" 1 "gimple" } } */
+/* { dg-final { scan-tree-dump-not "abort" "optimized" } } */
