8266388: C2: Improve constant ShiftCntV on x86

Reviewed-by: kvn

Author: Vladimir Ivanov

src/hotspot/cpu/x86/x86.ad

@@ -2119,6 +2119,10 @@ bool Matcher::pd_clone_node(Node* n, Node* m, Matcher::MStack& mstack) {
     mstack.push(m, Visit);
     return true;
   }
+  if (is_vshift_con_pattern(n, m)) { // ShiftV src (ShiftCntV con)
+    mstack.push(m, Visit);           // m = ShiftCntV
+    return true;
+  }
   return false;
 }
 

src/hotspot/share/opto/matcher.cpp

@@ -2025,7 +2025,7 @@ OptoReg::Name Matcher::find_receiver() {
   return OptoReg::as_OptoReg(regs.first());
 }
 
-bool Matcher::is_vshift_con_pattern(Node *n, Node *m) {
+bool Matcher::is_vshift_con_pattern(Node* n, Node* m) {
   if (n != NULL && m != NULL) {
     return VectorNode::is_vector_shift(n) &&
            VectorNode::is_vector_shift_count(m) && m->in(1)->is_Con();

src/hotspot/share/opto/matcher.hpp

@@ -121,7 +121,7 @@ class Matcher : public PhaseTransform {
   bool find_shared_visit(MStack& mstack, Node* n, uint opcode, bool& mem_op, int& mem_addr_idx);
   void find_shared_post_visit(Node* n, uint opcode);
 
-  bool is_vshift_con_pattern(Node *n, Node *m);
+  bool is_vshift_con_pattern(Node* n, Node* m);
 
   // Debug and profile information for nodes in old space:
   GrowableArray<Node_Notes*>* _old_node_note_array;