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comparison src/cpu/x86/vm/vtableStubs_x86_32.cpp @ 709:1d037ecd7960

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6827505: sizing logic for vtable and itable stubs needs self-check Summary: Asserts and comments to help maintain the correct sizing of certain stubs Reviewed-by: kvn
author jrose
date Wed, 08 Apr 2009 00:12:59 -0700
parents 9adddb8c0fc8
children bd02caa94611
comparison
equal deleted inserted replaced
708:f2049ae95c3d 709:1d037ecd7960
106 vtable_index, s->entry_point(), 106 vtable_index, s->entry_point(),
107 (int)(s->code_end() - s->entry_point()), 107 (int)(s->code_end() - s->entry_point()),
108 (int)(s->code_end() - __ pc())); 108 (int)(s->code_end() - __ pc()));
109 } 109 }
110 guarantee(__ pc() <= s->code_end(), "overflowed buffer"); 110 guarantee(__ pc() <= s->code_end(), "overflowed buffer");
111 // shut the door on sizing bugs
112 int slop = 3; // 32-bit offset is this much larger than an 8-bit one
113 assert(vtable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
111 114
112 s->set_exception_points(npe_addr, ame_addr); 115 s->set_exception_points(npe_addr, ame_addr);
113 return s; 116 return s;
114 } 117 }
115 118
179 itable_index, s->entry_point(), 182 itable_index, s->entry_point(),
180 (int)(s->code_end() - s->entry_point()), 183 (int)(s->code_end() - s->entry_point()),
181 (int)(s->code_end() - __ pc())); 184 (int)(s->code_end() - __ pc()));
182 } 185 }
183 guarantee(__ pc() <= s->code_end(), "overflowed buffer"); 186 guarantee(__ pc() <= s->code_end(), "overflowed buffer");
187 // shut the door on sizing bugs
188 int slop = 3; // 32-bit offset is this much larger than an 8-bit one
189 assert(itable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
184 190
185 s->set_exception_points(npe_addr, ame_addr); 191 s->set_exception_points(npe_addr, ame_addr);
186 return s; 192 return s;
187 } 193 }
188 194
194 return (DebugVtables ? 210 : 16) + (CountCompiledCalls ? 6 : 0); 200 return (DebugVtables ? 210 : 16) + (CountCompiledCalls ? 6 : 0);
195 } else { 201 } else {
196 // Itable stub size 202 // Itable stub size
197 return (DebugVtables ? 256 : 66) + (CountCompiledCalls ? 6 : 0); 203 return (DebugVtables ? 256 : 66) + (CountCompiledCalls ? 6 : 0);
198 } 204 }
205 // In order to tune these parameters, run the JVM with VM options
206 // +PrintMiscellaneous and +WizardMode to see information about
207 // actual itable stubs. Look for lines like this:
208 // itable #1 at 0x5551212[65] left over: 3
209 // Reduce the constants so that the "left over" number is >=3
210 // for the common cases.
211 // Do not aim at a left-over number of zero, because a
212 // large vtable or itable index (> 16) will require a 32-bit
213 // immediate displacement instead of an 8-bit one.
214 //
215 // The JVM98 app. _202_jess has a megamorphic interface call.
216 // The itable code looks like this:
217 // Decoding VtableStub itbl[1]@1
218 // mov 0x4(%ecx),%esi
219 // mov 0xe8(%esi),%edi
220 // lea 0x130(%esi,%edi,4),%edi
221 // add $0x7,%edi
222 // and $0xfffffff8,%edi
223 // lea 0x4(%esi),%esi
224 // mov (%edi),%ebx
225 // cmp %ebx,%eax
226 // je success
227 // loop:
228 // test %ebx,%ebx
229 // je throw_icce
230 // add $0x8,%edi
231 // mov (%edi),%ebx
232 // cmp %ebx,%eax
233 // jne loop
234 // success:
235 // mov 0x4(%edi),%edi
236 // mov (%esi,%edi,1),%ebx
237 // jmp *0x44(%ebx)
238 // throw_icce:
239 // jmp throw_ICCE_entry
199 } 240 }
200 241
201 int VtableStub::pd_code_alignment() { 242 int VtableStub::pd_code_alignment() {
202 return wordSize; 243 return wordSize;
203 } 244 }