AArch64: Fix scalar costing after removal of vectype from mid-end [PR121536]

commit g:fb59c5719c17a04ecfd58b5e566eccd6d2ac583a stops passing the scalar type
(confusingly named vectype) to the costing hook when doing scalar costing.

As a result, we could no longer distinguish between FPR and GPR scalar stmts.
A later commit also removed STMT_VINFO_VECTYPE from stmt_info.

This leaves the only remaining option to get the type of the original stmt in
the stmt_info.  This patch does this when we're performing scalar costing.

Ideally I'd refactor this a bit because a lot of the hooks just need to know if
it's FP or not, but this seems pointless with the ongoing costing churn.  So for
now this restores our costing.

gcc/ChangeLog:

	PR target/121536
	* config/aarch64/aarch64.cc (aarch64_vector_costs::add_stmt_cost): Set
	vectype from type of lhs of gimple stmt.

1 files changed, 11 insertions, 0 deletions

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index f88b7c9..83cd132 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -18045,6 +18045,17 @@ aarch64_vector_costs::add_stmt_cost (int count, vect_cost_for_stmt kind,
 				     tree vectype, int misalign,
 				     vect_cost_model_location where)
 {
+  /* When costing for scalars, vectype will be NULL; so look up the type via
+     stmt_info's statement.  */
+  if (m_costing_for_scalar && stmt_info)
+    {
+      gcc_assert (!vectype);
+      /* This won't work for e.g. gconds or other statements without a lhs,
+	 but those only work on GPR anyway and this is the best we can do.  */
+      if (tree lhs = gimple_get_lhs (STMT_VINFO_STMT (stmt_info)))
+	vectype = TREE_TYPE (lhs);
+    }
+
   fractional_cost stmt_cost
     = aarch64_builtin_vectorization_cost (kind, vectype, misalign);