[gcc r16-6732] VN: Fix VN ICE for large _BitInt types

[Kito Cheng]

https://gcc.gnu.org/g:cbb9d3815201cfb8869140fc80f0cee19f004a3f

commit r16-6732-gcbb9d3815201cfb8869140fc80f0cee19f004a3f
Author: Kito Cheng <kito.cheng@sifive.com>
Date:   Mon Dec 29 14:14:25 2025 +0800

    VN: Fix VN ICE for large _BitInt types
    
    gcc.dg/torture/bitint-18.c triggers an ICE in push_partial_def when
    compiling for RISC-V with -O2.  The issue occurs because
    build_nonstandard_integer_type cannot handle bit widths larger than
    MAX_FIXED_MODE_SIZE.
    
    For BITINT_TYPE with maxsizei > MAX_FIXED_MODE_SIZE, use build_bitint_type
    instead of build_nonstandard_integer_type, similar to what tree-sra.cc does.
    
    gcc/ChangeLog:
    
            * tree-ssa-sccvn.cc (vn_walk_cb_data::push_partial_def): Use
            build_bitint_type for BITINT_TYPE when maxsizei exceeds
            MAX_FIXED_MODE_SIZE.

Diff:
---
 gcc/tree-ssa-sccvn.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index b152dcb5943f..13deccb6c6b1 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -2316,7 +2316,13 @@ vn_walk_cb_data::push_partial_def (pd_data pd,
   /* Make sure to interpret in a type that has a range covering the whole
      access size.  */
   if (INTEGRAL_TYPE_P (vr->type) && maxsizei != TYPE_PRECISION (vr->type))
-    type = build_nonstandard_integer_type (maxsizei, TYPE_UNSIGNED (type));
+    {
+      if (TREE_CODE (vr->type) == BITINT_TYPE
+	  && maxsizei > MAX_FIXED_MODE_SIZE)
+	type = build_bitint_type (maxsizei, TYPE_UNSIGNED (type));
+      else
+	type = build_nonstandard_integer_type (maxsizei, TYPE_UNSIGNED (type));
+    }
   tree val;
   if (BYTES_BIG_ENDIAN)
     {