[gcc r15-10679] expand: Handle variable-length vector constructors with debug [PR123392]

[Tejas Belagod]

https://gcc.gnu.org/g:062b2dfdc9c17c25ef60ae498f2518ce3b977eb9

commit r15-10679-g062b2dfdc9c17c25ef60ae498f2518ce3b977eb9
Author: Tejas Belagod <tejas.belagod@arm.com>
Date:   Tue Jan 13 16:58:38 2026 +0000

    expand: Handle variable-length vector constructors with debug [PR123392]
    
    Variable-length Vector initializer constructors currently only work in
    non-debug mode.  It ICEs when compiled with -g.  This patch fixes it to handle
    variable-length vector intialization by limiting the constructor elements to
    the lower bound of the variable length poly which is also the maximum number
    of elements allowed in the initializer.
    
            PR middle-end/123392
    gcc/
            * cfgexpand.cc (expand_debug_expr): Handle variable-length initializer
            for CONSTRUCTOR.
    
    gcc/testsuite/
    
            * gcc.target/aarch64/sve/acle/general/pr123392.c: New.

Diff:
---
 gcc/cfgexpand.cc                                             |  6 ++----
 gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr123392.c | 10 ++++++++++
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/gcc/cfgexpand.cc b/gcc/cfgexpand.cc
index 981faf36e93e..e2455981b4ed 100644
--- a/gcc/cfgexpand.cc
+++ b/gcc/cfgexpand.cc
@@ -5635,12 +5635,10 @@ expand_debug_expr (tree exp)
       else if (TREE_CODE (TREE_TYPE (exp)) == VECTOR_TYPE)
 	{
 	  unsigned i;
-	  unsigned HOST_WIDE_INT nelts;
+	  poly_uint64 elts = TYPE_VECTOR_SUBPARTS (TREE_TYPE (exp));
+	  unsigned HOST_WIDE_INT nelts = constant_lower_bound (elts);
 	  tree val;
 
-	  if (!TYPE_VECTOR_SUBPARTS (TREE_TYPE (exp)).is_constant (&nelts))
-	    goto flag_unsupported;
-
 	  op0 = gen_rtx_CONCATN (mode, rtvec_alloc (nelts));
 
 	  FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (exp), i, val)
diff --git a/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr123392.c b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr123392.c
new file mode 100644
index 000000000000..5fe9848998d0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/sve/acle/general/pr123392.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -g" } */
+
+#include <arm_sve.h>
+
+svint32_t res (int32_t *a)
+{
+  svint32_t s = { a[0], a[1], a[2], a[3] };
+  return s;
+}