8335713: Enhance vectorization analysis

Reviewed-by: roland, andrew
Backport-of: 3c05ad2290936ec9abc3f271cb6bf89e18c3eea7

Author: martinuy

hotspot/src/share/vm/opto/superword.cpp

@@ -2735,10 +2735,30 @@ bool SWPointer::scaled_iv_plus_offset(Node* n) {
     }
   } else if (opc == Op_SubI) {
     if (scaled_iv(n->in(1)) && offset_plus_k(n->in(2), true)) {
+      // (scale * iv) - (offset1 + invar1)
+      // Subtraction handled via "negate" flag of "offset_plus_k".
       return true;
     }
-    if (scaled_iv(n->in(2)) && offset_plus_k(n->in(1))) {
-      _scale *= -1;
+    SWPointer tmp(this);
+    if (tmp.scaled_iv(n->in(2)) && offset_plus_k(n->in(1))) {
+      // (offset1 + invar1) - (scale * iv)
+      // Subtraction handled explicitly below.
+      assert(_scale == 0, "shouldn't be set yet");
+      // _scale = -tmp._scale
+      if (!try_MulI_no_overflow(-1, tmp._scale, _scale)) {
+        return false; // mul overflow.
+      }
+      // _offset -= tmp._offset
+      if (!try_SubI_no_overflow(_offset, tmp._offset, _offset)) {
+        return false; // sub overflow.
+      }
+
+      // SWPointer tmp does not have an integer part to be forwarded
+      // (tmp._has_int_index_after_convI2L is false) because n is a SubI, all
+      // nodes above must also be of integer type (ConvL2I is not handled
+      // to allow a long) and ConvI2L (the only node that can add an integer
+      // part) won't be present.
+
       return true;
     }
   }
@@ -2766,7 +2786,9 @@ bool SWPointer::scaled_iv(Node* n) {
     }
   } else if (opc == Op_LShiftI) {
     if (n->in(1) == iv() && n->in(2)->is_Con()) {
-      _scale = 1 << n->in(2)->get_int();
+      if (!try_LShiftI_no_overflow(1, n->in(2)->get_int(), _scale)) {
+        return false; // shift overflow.
+      }
       return true;
     }
   } else if (opc == Op_ConvI2L && !has_iv()) {
@@ -2792,15 +2814,28 @@ bool SWPointer::scaled_iv(Node* n) {
     if (tmp.scaled_iv_plus_offset(n->in(1)) && tmp.has_iv()) {
       // We successfully matched an integer index, of the form:
       //   int_index = int_offset + int_invar + int_scale * iv
+      // Forward scale.
+      assert(_scale == 0 && tmp._scale != 0, "iv only found just now");
+      _scale = tmp._scale;
+      // Accumulate offset.
+      if (!try_AddI_no_overflow(_offset, tmp._offset, _offset)) {
+        return false; // add overflow.
+      }
+      // Forward invariant if not already found.
+      if (tmp._invar != NULL) {
+        if (_invar != NULL) {
+          return false;
+        }
+        _invar = tmp._invar;
+        _negate_invar = tmp._negate_invar;
+      }
+      // Set info about the int_index:
+      assert(!_has_int_index_after_convI2L, "no previous int_index discovered");
       _has_int_index_after_convI2L = true;
       _int_index_after_convI2L_offset = tmp._offset;
       _int_index_after_convI2L_invar  = tmp._invar;
       _int_index_after_convI2L_scale  = tmp._scale;
-    }
 
-    // Now parse it again for the real SWPointer. This makes sure that the int_offset, int_invar,
-    // and int_scale are properly added to the final SWPointer's offset, invar, and scale.
-    if (scaled_iv_plus_offset(n->in(1))) {
       return true;
     }
   } else if (opc == Op_LShiftL) {
@@ -2811,20 +2846,22 @@ bool SWPointer::scaled_iv(Node* n) {
       SWPointer tmp(this);
       if (tmp.scaled_iv_plus_offset(n->in(1))) {
         if (tmp._invar == NULL) {
-          int scale = (int)(n->in(2)->get_int());
-          int mult = 1 << scale;
+          int shift = (int)(n->in(2)->get_int());
           // Accumulate scale.
-          _scale   = tmp._scale  * ((jint)mult);
+          if (!try_LShiftI_no_overflow(tmp._scale, shift, _scale)) {
+            return false; // shift overflow.
+          }
           // Accumulate offset.
           jint shifted_offset = 0;
-          if (!try_LShiftI_no_overflow(tmp._offset, scale, shifted_offset)) {
+          if (!try_LShiftI_no_overflow(tmp._offset, shift, shifted_offset)) {
             return false; // shift overflow.
           }
           if (!try_AddI_no_overflow(_offset, shifted_offset, _offset)) {
             return false; // add overflow.
           }
 
           // Forward info about the int_index:
+          assert(!_has_int_index_after_convI2L, "no previous int_index discovered");
           _has_int_index_after_convI2L = tmp._has_int_index_after_convI2L;
           _int_index_after_convI2L_offset = tmp._int_index_after_convI2L_offset;
           _int_index_after_convI2L_invar  = tmp._int_index_after_convI2L_invar;
@@ -2933,6 +2970,9 @@ bool SWPointer::try_AddSubI_no_overflow(jint offset1, jint offset2, bool is_sub,
 }
 
 bool SWPointer::try_LShiftI_no_overflow(jint offset, int shift, jint& result) {
+  if (shift < 0 || shift > 31) {
+    return false;
+  }
   jlong long_offset = java_shift_left((jlong)(offset), (julong)((jlong)(shift)));
   jint  int_offset  = java_shift_left(        offset,  (juint)((jint)(shift)));
   if (long_offset != int_offset) {
@@ -2942,6 +2982,16 @@ bool SWPointer::try_LShiftI_no_overflow(jint offset, int shift, jint& result) {
   return true;
 }
 
+bool SWPointer::try_MulI_no_overflow(jint offset1, jint offset2, jint& result) {
+  jlong long_offset = java_multiply((jlong)(offset1), (jlong)(offset2));
+  jint  int_offset  = java_multiply(        offset1,          offset2);
+  if (long_offset != int_offset) {
+    return false;
+  }
+  result = int_offset;
+  return true;
+}
+
 //----------------------------print------------------------
 void SWPointer::print() {
 #ifndef PRODUCT

hotspot/src/share/vm/opto/superword.hpp

@@ -614,6 +614,7 @@ class SWPointer VALUE_OBJ_CLASS_SPEC {
   static bool try_SubI_no_overflow(jint offset1, jint offset2, jint& result);
   static bool try_AddSubI_no_overflow(jint offset1, jint offset2, bool is_sub, jint& result);
   static bool try_LShiftI_no_overflow(jint offset1, int offset2, jint& result);
+  static bool try_MulI_no_overflow(jint offset1, jint offset2, jint& result);
 
 };