[gcc r17-3564] forwprop: Add LMK_INVALID and check for it

https://gcc.gnu.org/g:a15a2cee730ccdd5894ca6ece783f6fe27cb3e20

commit r17-3564-ga15a2cee730ccdd5894ca6ece783f6fe27cb3e20
Author: Andrea Pinski <[email protected]>
Date:   Sat Aug 22 19:45:16 2026 -0700

    forwprop: Add LMK_INVALID and check for it
    
    This adds some checks to make sure only a full initialized
    long_mul_summand is added the vector.
    The checks are only enabled for non release checking.
    
    gcc/ChangeLog:
    
            * tree-ssa-forwprop.cc (enum long_mul_kind): Add LMK_INVALID.
            (long_mul_set_summand): Add default case to switch.
            (long_mul_summand_compare): Add checking to make sure
            the kinds are not LMK_INVALID.
            (long_mul_find_summand): Likewise.
            (long_mul_classify_chain): Add checking right before
            the push to check for LMK_INVALID.
            (match_long_mul_phi): Simpilify stynx for initializing carry.
    
    Signed-off-by: Andrea Pinski <[email protected]>

Diff:
---
 gcc/tree-ssa-forwprop.cc | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/gcc/tree-ssa-forwprop.cc b/gcc/tree-ssa-forwprop.cc
index ff10baf10193..6575aad0e59c 100644
--- a/gcc/tree-ssa-forwprop.cc
+++ b/gcc/tree-ssa-forwprop.cc
@@ -3733,6 +3733,7 @@ static constexpr unsigned LONG_MUL_MAX_EXTRAS = 4;
 namespace {
 
 enum long_mul_kind : unsigned char {
+  LMK_INVALID,
   LMK_MUL_HIHI,
   LMK_MUL_LOLO,
   LMK_MUL_HILO,
@@ -3852,6 +3853,8 @@ long_mul_set_summand (long_mul_summand *info, long_mul_kind kind,
   int shift_idx = -1;
   switch (kind)
     {
+    default:
+      gcc_unreachable ();
     case LMK_MUL_HIHI:
     case LMK_MUL_LOLO:
     case LMK_MUL_HILO:
@@ -4099,6 +4102,8 @@ long_mul_summand_compare (const void *a, const void *b)
 {
   const long_mul_summand *sa = (const long_mul_summand *) a;
   const long_mul_summand *sb = (const long_mul_summand *) b;
+  gcc_checking_assert (sa->kind != LMK_INVALID);
+  gcc_checking_assert (sb->kind != LMK_INVALID);
   if (sa->kind != sb->kind)
     return (int) sa->kind - (int) sb->kind;
   return (int) sa->extract - (int) sb->extract;
@@ -4185,6 +4190,7 @@ static const long_mul_summand *
 long_mul_find_summand (const vec<long_mul_summand> &summands,
 		       long_mul_kind kind)
 {
+  gcc_checking_assert (kind != LMK_INVALID);
   for (const long_mul_summand &s : summands)
     if (s.kind == kind)
       return &s;
@@ -4584,9 +4590,12 @@ long_mul_classify_chain (gimple *stmt, tree_code outer, tree lhs_type,
 	   LONG_MUL_MAX_SUMMANDS + LONG_MUL_MAX_EXTRAS + 1> summands;
   for (tree leaf : leaves)
     {
-      long_mul_summand s;
+      long_mul_summand s{};
       if (long_mul_classify_summand (leaf, &s))
-	summands.quick_push (s);
+	{
+	  gcc_checking_assert (s.kind != LMK_INVALID);
+	  summands.quick_push (s);
+	}
       else if (extras_out && extras_out->length () < LONG_MUL_MAX_EXTRAS)
 	extras_out->safe_push (leaf);
       else
@@ -4596,7 +4605,10 @@ long_mul_classify_chain (gimple *stmt, tree_code outer, tree lhs_type,
 	}
     }
   if (extra)
-    summands.quick_push (*extra);
+    {
+      gcc_checking_assert (extra->kind != LMK_INVALID);
+      summands.quick_push (*extra);
+    }
   if (summands.length () < 2
       || summands.length () > LONG_MUL_MAX_SUMMANDS)
     return NULL;
@@ -4692,7 +4704,7 @@ match_long_mul_phi (gphi *phi)
 
   /* Classify sum and populate the carry summand directly.  Most
      specific first, mirroring long_mul_classify_carry's order.  */
-  long_mul_summand carry = {};
+  long_mul_summand carry{};
   tree sum_ops[LONG_MUL_MAX_CAPTURES];
   unsigned HOST_WIDE_INT shift_amt
     = wi::exact_log2 (wi::to_wide (cca_ops[3]));