Hi,

PR122126 had been fixed on trunk, gcc-14 and gcc-15. But not on gcc-13, I had
backported commit 7d966cc35ad01d70cd9bfb6f531c938a7b6110b7 on gcc-13, but did
not test it before pushing, therefore had to revert it.

I have made a minor change to the original commit that fixed PR122126 for the
gcc-13 branch. Bootstrapped and regtested on releases/gcc-13 on powerpc64le
with no regressions.

Is this OK to merge to releases/gcc-13?

Thanks and regards,
Avinash Jayakar

The function gimple_expand_vec_set_expr in the isel pass, converted
VIEW_CONVERT_EXPR to VEC_SET_EXPR without checking the bounds on the index,
which cause ICE on targets that supported VEC_SET_EXPR like x86 and powerpc.
This patch adds a bound check on the index operand and rejects the conversion
if index is out of bound.

2026-01-05  Avinash Jayakar  <[email protected]>

gcc/ChangeLog:
        PR tree-optimization/122126
        * gimple-isel.cc (gimple_expand_vec_set_extract_expr): Add bound check.

gcc/testsuite/ChangeLog:
        PR tree-optimization/122126
        * gcc.dg/pr122126_vextr.c: New test.
        * gcc.dg/pr122126_vset.c: New test.
---
 gcc/gimple-isel.cc                    | 9 +++++++++
 gcc/testsuite/gcc.dg/pr122126_vextr.c | 9 +++++++++
 gcc/testsuite/gcc.dg/pr122126_vset.c  | 9 +++++++++
 3 files changed, 27 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/pr122126_vextr.c
 create mode 100644 gcc/testsuite/gcc.dg/pr122126_vset.c

diff --git a/gcc/gimple-isel.cc b/gcc/gimple-isel.cc
index 760029d27c9..f7eabeca647 100644
--- a/gcc/gimple-isel.cc
+++ b/gcc/gimple-isel.cc
@@ -76,6 +76,15 @@ gimple_expand_vec_set_expr (struct function *fun, 
gimple_stmt_iterator *gsi)
     {
       tree pos = TREE_OPERAND (lhs, 1);
       tree view_op0 = TREE_OPERAND (op0, 0);
+
+      // if index is a constant, then check the bounds
+      poly_uint64 idx_poly;
+      if (poly_int_tree_p (pos, &idx_poly))
+       {
+         poly_uint64 nelts = TYPE_VECTOR_SUBPARTS (TREE_TYPE (view_op0));
+         if (known_gt (idx_poly, nelts))
+           return false;
+       }
       machine_mode outermode = TYPE_MODE (TREE_TYPE (view_op0));
       if ((auto_var_in_fn_p (view_op0, fun->decl)
           || (VAR_P (view_op0) && DECL_HARD_REGISTER (view_op0)))
diff --git a/gcc/testsuite/gcc.dg/pr122126_vextr.c 
b/gcc/testsuite/gcc.dg/pr122126_vextr.c
new file mode 100644
index 00000000000..b598aa01091
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr122126_vextr.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-mavx2" { target avx2 } } */
+
+#define vect16 __attribute__((vector_size(16)))
+void ub_set() {
+  volatile vect16 unsigned BS_VAR_0;
+  unsigned a = BS_VAR_0[12];
+}
diff --git a/gcc/testsuite/gcc.dg/pr122126_vset.c 
b/gcc/testsuite/gcc.dg/pr122126_vset.c
new file mode 100644
index 00000000000..85b2c68247b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr122126_vset.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-additional-options "-mavx2" { target avx2 } } */
+
+#define vect16 __attribute__((vector_size(16)))
+void ub_set() {
+  volatile vect16 unsigned BS_VAR_0;
+  BS_VAR_0[12] = 4;
+}
-- 
2.51.0

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