lower-bitint: Fix up handle_operand_addr INTEGER_CST handling [PR113361]

As the testcase shows, the INTEGER_CST handling in handle_operand_addr
(i.e. what is used when passing address of an integer to a bitint library
routine) wasn't correct.  If the minimum precision to represent an
INTEGER_CST is smaller or equal to limb_prec, the code correctly uses
m_limb_type; if the minimum precision of a _BitInt INTEGER_CST is large
enough such that the bitint is middle, large or huge, everything is fine
too.  But the code wasn't handling correctly e.g. __int128 constants which
need more than limb_prec bits or _BitInt constants which on the architecture
are considered small (say have DImode limb_mode, TImode abi_limb_mode and
for [65, 128] bits use TImode scalar like the proposed aarch64 patch).
Best would be to use an array of 2/3/4 limbs in that case, but we'd need to
convert the INTEGER_CST to a CONSTRUCTOR in the right endianity etc.,
so the code was using mid_min_prec to enforce a middle _BitInt precision.
Except that mid_min_prec can be 0 and not computed yet, or it doesn't have
to be the smallest middle _BitInt precision, just the smallest so far
encountered.  So, on the testcase one possibility was that it used precision
65 from mid_min_prec, even when the INTEGER_CST actually needed larger
minimum precision (96 bits at least), or crashed when mid_min_prec was 0.

The patch fixes it in 2 hunks, the first makes sure we actually try to
create a BITINT_TYPE for the > limb_prec cases like __int128, and the second
instead of using mid_min_prec attempts to increase mp precision until it
isn't small anymore.

2024-01-13  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/113361
	* gimple-lower-bitint.cc (bitint_large_huge::handle_operand_addr):
	Fix up determination of the type for > limb_prec constants.

	* gcc.dg/torture/bitint-47.c: New test.

2 files changed, 43 insertions, 6 deletions

diff --git a/gcc/gimple-lower-bitint.cc b/gcc/gimple-lower-bitint.cc
index 4a0cb55..ac7fa30 100644
--- a/gcc/gimple-lower-bitint.cc
+++ b/gcc/gimple-lower-bitint.cc
@@ -2227,7 +2227,9 @@ bitint_large_huge::handle_operand_addr (tree op, gimple *stmt,
       mp = CEIL (min_prec, limb_prec) * limb_prec;
       if (mp == 0)
 	mp = 1;
-      if (mp >= (unsigned) TYPE_PRECISION (TREE_TYPE (op)))
+      if (mp >= (unsigned) TYPE_PRECISION (TREE_TYPE (op))
+	  && (TREE_CODE (TREE_TYPE (op)) == BITINT_TYPE
+	      || TYPE_PRECISION (TREE_TYPE (op)) <= limb_prec))
 	type = TREE_TYPE (op);
       else
 	type = build_bitint_type (mp, 1);
@@ -2237,11 +2239,15 @@ bitint_large_huge::handle_operand_addr (tree op, gimple *stmt,
 	  if (TYPE_PRECISION (type) <= limb_prec)
 	    type = m_limb_type;
 	  else
-	    /* This case is for targets which e.g. have 64-bit
-	       limb but categorize up to 128-bits _BitInts as
-	       small.  We could use type of m_limb_type[2] and
-	       similar instead to save space.  */
-	    type = build_bitint_type (mid_min_prec, 1);
+	    {
+	      while (bitint_precision_kind (mp) == bitint_prec_small)
+		mp += limb_prec;
+	      /* This case is for targets which e.g. have 64-bit
+		 limb but categorize up to 128-bits _BitInts as
+		 small.  We could use type of m_limb_type[2] and
+		 similar instead to save space.  */
+	      type = build_bitint_type (mp, 1);
+	    }
 	}
       if (prec_stored)
 	{
diff --git a/gcc/testsuite/gcc.dg/torture/bitint-47.c b/gcc/testsuite/gcc.dg/torture/bitint-47.c
new file mode 100644
index 0000000..fa70d80
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/bitint-47.c
@@ -0,0 +1,31 @@
+/* PR tree-optimization/113361 */
+/* { dg-do run { target { bitint && int128 } } } */
+/* { dg-options "-std=gnu23" } */
+/* { dg-skip-if "" { ! run_expensive_tests }  { "*" } { "-O0" "-O2" } } */
+/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
+
+#if __BITINT_MAXWIDTH__ >= 129
+int
+foo (_BitInt(65) x)
+{
+  return __builtin_mul_overflow_p ((__int128) 0xffffffff << 64, x, (_BitInt(129)) 0);
+}
+
+int
+bar (_BitInt(63) x)
+{
+  return __builtin_mul_overflow_p ((__int128) 0xffffffff << 64, x, (_BitInt(129)) 0);
+}
+#endif
+
+int
+main ()
+{
+#if __BITINT_MAXWIDTH__ >= 129
+  if (!foo (5167856845))
+    __builtin_abort ();
+  if (!bar (5167856845))
+    __builtin_abort ();
+#endif
+  return 0;
+}