From: Jakub Jelinek <jakub@redhat.com>
Date: Fri, 12 Jan 2024 10:23:27 +0000 (+0100)
Subject: lower-bitint: Fix up handling of unsigned INTEGER_CSTs operands with lots of 1s in... 
X-Git-Tag: basepoints/gcc-15~2957
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c75579169eba269a7c339d80b5ac0239f36a58b3;p=thirdparty%2Fgcc.git

lower-bitint: Fix up handling of unsigned INTEGER_CSTs operands with lots of 1s in the upper bits [PR113334]

For INTEGER_CST operands, the code decides if it should emit the whole
INTEGER_CST into memory, or if there are enough upper bits either all 0s
or all 1s to warrant an optimization, where we use memory for lower limbs
or even just an INTEGER_CST for least significant limb and fill in the
rest of limbs with 0s or 1s.  Unfortunately when not using
bitint_min_cst_precision, the code was using tree_int_cst_sgn (op) < 0
to determine whether to fill in the upper bits with 1s or 0s.  That is
incorrect for TYPE_UNSIGNED INTEGER_CSTs which have higher limbs full of
ones, we really want to check here whether the most significant bit is
set or clear.

Fixed thusly.

2024-01-12  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113334
	* gimple-lower-bitint.cc (bitint_large_huge::handle_operand): Use
	wi::neg_p (wi::to_wide (op)) instead of tree_int_cst_sgn (op) < 0
	to determine if number should be extended by all ones rather than zero
	extended.

	* gcc.dg/torture/bitint-46.c: New test.
---

diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc
index f1e4cd01cb06..4a0cb55a731d 100644
--- a/gcc/gimple-lower-bitint.cc
+++ b/gcc/gimple-lower-bitint.cc
@@ -997,7 +997,7 @@ bitint_large_huge::handle_operand (tree op, tree idx)
 	{
 	  unsigned int prec = TYPE_PRECISION (TREE_TYPE (op));
 	  unsigned rem = prec % (2 * limb_prec);
-	  int ext = tree_int_cst_sgn (op) < 0 ? -1 : 0;
+	  int ext = wi::neg_p (wi::to_wide (op)) ? -1 : 0;
 	  tree c = m_data[m_data_cnt];
 	  unsigned min_prec = TYPE_PRECISION (TREE_TYPE (c));
 	  g = gimple_build_cond (LT_EXPR, idx,
diff --git a/gcc/testsuite/gcc.dg/torture/bitint-46.c b/gcc/testsuite/gcc.dg/torture/bitint-46.c
new file mode 100644
index 000000000000..af0a3d1e4e06
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/bitint-46.c
@@ -0,0 +1,32 @@
+/* PR tree-optimization/113334 */
+/* { 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" } { "" } } */
+
+#if __BITINT_MAXWIDTH__ >= 384
+__attribute__((noipa)) _BitInt(384)
+foo (int s)
+{
+  _BitInt(384) z = (-(unsigned _BitInt(384)) 4) >> s;
+  return z;
+}
+#endif
+
+int
+main ()
+{
+#if __BITINT_MAXWIDTH__ >= 384
+  if (foo (59) != 0x1fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffwb)
+    __builtin_abort ();
+  if (foo (0) != -4wb)
+    __builtin_abort ();
+  if (foo (1) != 0x7ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffewb)
+    __builtin_abort ();
+  if (foo (11) != 0x001fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffwb)
+    __builtin_abort ();
+  if (foo (123) != 0x1fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffwb)
+    __builtin_abort ();
+#endif
+  return 0;
+}