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src/share/vm/opto/matcher.hpp

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rev 7602 : 8064457: Introduce compressed oops mode disjoint base and improve compressed heap handling.

*** 431,440 **** --- 431,447 ---- // decode narrow_oop_reg, oop_reg // only 'shift' // [oop_reg + offset] // NullCheck oop_reg // inline static bool gen_narrow_oop_implicit_null_checks() { + // Advice matcher to perform null checks on the narrow oop side. + // Implicit checks are not possible on the uncompressed oop side anyway + // (at least not for read accesses). + // Performs significantly better (especially on Power 6). + if (!os::zero_page_read_protected()) { + return true; + } return Universe::narrow_oop_use_implicit_null_checks() && (narrow_oop_use_complex_address() || Universe::narrow_oop_base() != NULL); }
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