1.1 --- a/src/share/vm/opto/matcher.hpp Tue Jun 01 11:48:33 2010 -0700
1.2 +++ b/src/share/vm/opto/matcher.hpp Wed Jun 02 22:45:42 2010 -0700
1.3 @@ -352,6 +352,38 @@
1.4 // registers? True for Intel but false for most RISCs
1.5 static const bool clone_shift_expressions;
1.6
1.7 + static bool narrow_oop_use_complex_address();
1.8 +
1.9 + // Generate implicit null check for narrow oops if it can fold
1.10 + // into address expression (x64).
1.11 + //
1.12 + // [R12 + narrow_oop_reg<<3 + offset] // fold into address expression
1.13 + // NullCheck narrow_oop_reg
1.14 + //
1.15 + // When narrow oops can't fold into address expression (Sparc) and
1.16 + // base is not null use decode_not_null and normal implicit null check.
1.17 + // Note, decode_not_null node can be used here since it is referenced
1.18 + // only on non null path but it requires special handling, see
1.19 + // collect_null_checks():
1.20 + //
1.21 + // decode_not_null narrow_oop_reg, oop_reg // 'shift' and 'add base'
1.22 + // [oop_reg + offset]
1.23 + // NullCheck oop_reg
1.24 + //
1.25 + // With Zero base and when narrow oops can not fold into address
1.26 + // expression use normal implicit null check since only shift
1.27 + // is needed to decode narrow oop.
1.28 + //
1.29 + // decode narrow_oop_reg, oop_reg // only 'shift'
1.30 + // [oop_reg + offset]
1.31 + // NullCheck oop_reg
1.32 + //
1.33 + inline static bool gen_narrow_oop_implicit_null_checks() {
1.34 + return Universe::narrow_oop_use_implicit_null_checks() &&
1.35 + (narrow_oop_use_complex_address() ||
1.36 + Universe::narrow_oop_base() != NULL);
1.37 + }
1.38 +
1.39 // Is it better to copy float constants, or load them directly from memory?
1.40 // Intel can load a float constant from a direct address, requiring no
1.41 // extra registers. Most RISCs will have to materialize an address into a
