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comparison src/share/vm/opto/lcm.cpp @ 642:660978a2a31a

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6791178: Specialize for zero as the compressed oop vm heap base Summary: Use zero based compressed oops if java heap is below 32gb and unscaled compressed oops if java heap is below 4gb. Reviewed-by: never, twisti, jcoomes, coleenp
author kvn
date Thu, 12 Mar 2009 10:37:46 -0700
parents 3b5ac9e7e6ea
children bd441136a5ce
comparison
equal deleted inserted replaced
641:6af0a709d52b 642:660978a2a31a
156 if( val->bottom_type()->isa_narrowoop() && 156 if( val->bottom_type()->isa_narrowoop() &&
157 MacroAssembler::needs_explicit_null_check(offset) ) 157 MacroAssembler::needs_explicit_null_check(offset) )
158 continue; // Give up if offset is beyond page size 158 continue; // Give up if offset is beyond page size
159 // cannot reason about it; is probably not implicit null exception 159 // cannot reason about it; is probably not implicit null exception
160 } else { 160 } else {
161 const TypePtr* tptr = base->bottom_type()->is_ptr(); 161 const TypePtr* tptr;
162 if (UseCompressedOops && Universe::narrow_oop_shift() == 0) {
163 // 32-bits narrow oop can be the base of address expressions
164 tptr = base->bottom_type()->make_ptr();
165 } else {
166 // only regular oops are expected here
167 tptr = base->bottom_type()->is_ptr();
168 }
162 // Give up if offset is not a compile-time constant 169 // Give up if offset is not a compile-time constant
163 if( offset == Type::OffsetBot || tptr->_offset == Type::OffsetBot ) 170 if( offset == Type::OffsetBot || tptr->_offset == Type::OffsetBot )
164 continue; 171 continue;
165 offset += tptr->_offset; // correct if base is offseted 172 offset += tptr->_offset; // correct if base is offseted
166 if( MacroAssembler::needs_explicit_null_check(offset) ) 173 if( MacroAssembler::needs_explicit_null_check(offset) )