Hi!
The following patch is miscompiled, because convert_to_integer_1 for
LSHIFT_EXPR tests if the INTEGER_CST shift count is too high, but
incorrectly compares it against TYPE_SIZE rather than TYPE_PRECISION.
The type in question is unsigned _BitInt(1), which has TYPE_PRECISION 1,
TYPE_SIZE 8, and the shift count is 2 in that case.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2024-01-25 Jakub Jelinek <ja...@redhat.com>
PR middle-end/113574
* convert.cc (convert_to_integer_1) <case LSHIFT_EXPR>: Compare shift
count against TYPE_PRECISION rather than TYPE_SIZE.
* gcc.dg/torture/bitint-52.c: New test.
--- gcc/convert.cc.jj 2024-01-03 11:51:24.000000000 +0100
+++ gcc/convert.cc 2024-01-24 17:29:56.328124611 +0100
@@ -762,7 +762,8 @@ convert_to_integer_1 (tree type, tree ex
{
/* If shift count is less than the width of the truncated type,
really shift. */
- if (tree_int_cst_lt (TREE_OPERAND (expr, 1), TYPE_SIZE (type)))
+ if (wi::to_widest (TREE_OPERAND (expr, 1))
+ < TYPE_PRECISION (type))
/* In this case, shifting is like multiplication. */
goto trunc1;
else
--- gcc/testsuite/gcc.dg/torture/bitint-52.c.jj 2024-01-24 17:33:42.174986825
+0100
+++ gcc/testsuite/gcc.dg/torture/bitint-52.c 2024-01-24 17:33:33.395108814
+0100
@@ -0,0 +1,23 @@
+/* PR middle-end/113574 */
+/* { dg-do run { target bitint } } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "*" } { "-O0" "-O2" } } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
+
+unsigned _BitInt(1) a;
+unsigned _BitInt(8) b;
+
+void
+foo (unsigned _BitInt(16) x)
+{
+ a += (x << 2) | b;
+}
+
+int
+main ()
+{
+ foo (0xfef1uwb);
+ if (a)
+ __builtin_abort ();
+ return 0;
+}
Jakub
