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comparison src/cpu/x86/vm/vtableStubs_x86_64.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
104 vtable_index, s->entry_point(), 104 vtable_index, s->entry_point(),
105 (int)(s->code_end() - s->entry_point()), 105 (int)(s->code_end() - s->entry_point()),
106 (int)(s->code_end() - __ pc())); 106 (int)(s->code_end() - __ pc()));
107 } 107 }
108 guarantee(__ pc() <= s->code_end(), "overflowed buffer"); 108 guarantee(__ pc() <= s->code_end(), "overflowed buffer");
109 // shut the door on sizing bugs
110 int slop = 3; // 32-bit offset is this much larger than an 8-bit one
111 assert(vtable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
109 112
110 s->set_exception_points(npe_addr, ame_addr); 113 s->set_exception_points(npe_addr, ame_addr);
111 return s; 114 return s;
112 } 115 }
113 116
189 itable_index, s->entry_point(), 192 itable_index, s->entry_point(),
190 (int)(s->code_end() - s->entry_point()), 193 (int)(s->code_end() - s->entry_point()),
191 (int)(s->code_end() - __ pc())); 194 (int)(s->code_end() - __ pc()));
192 } 195 }
193 guarantee(__ pc() <= s->code_end(), "overflowed buffer"); 196 guarantee(__ pc() <= s->code_end(), "overflowed buffer");
197 // shut the door on sizing bugs
198 int slop = 3; // 32-bit offset is this much larger than an 8-bit one
199 assert(itable_index > 10 || __ pc() + slop <= s->code_end(), "room for 32-bit offset");
194 200
195 s->set_exception_points(npe_addr, ame_addr); 201 s->set_exception_points(npe_addr, ame_addr);
196 return s; 202 return s;
197 } 203 }
198 204
204 } else { 210 } else {
205 // Itable stub size 211 // Itable stub size
206 return (DebugVtables ? 512 : 72) + (CountCompiledCalls ? 13 : 0) + 212 return (DebugVtables ? 512 : 72) + (CountCompiledCalls ? 13 : 0) +
207 (UseCompressedOops ? 32 : 0); // 2 leaqs 213 (UseCompressedOops ? 32 : 0); // 2 leaqs
208 } 214 }
215 // In order to tune these parameters, run the JVM with VM options
216 // +PrintMiscellaneous and +WizardMode to see information about
217 // actual itable stubs. Look for lines like this:
218 // itable #1 at 0x5551212[71] left over: 3
219 // Reduce the constants so that the "left over" number is >=3
220 // for the common cases.
221 // Do not aim at a left-over number of zero, because a
222 // large vtable or itable index (>= 32) will require a 32-bit
223 // immediate displacement instead of an 8-bit one.
224 //
225 // The JVM98 app. _202_jess has a megamorphic interface call.
226 // The itable code looks like this:
227 // Decoding VtableStub itbl[1]@12
228 // mov 0x8(%rsi),%r10
229 // mov 0x198(%r10),%r11d
230 // lea 0x218(%r10,%r11,8),%r11
231 // lea 0x8(%r10),%r10
232 // mov (%r11),%rbx
233 // cmp %rbx,%rax
234 // je success
235 // loop:
236 // test %rbx,%rbx
237 // je throw_icce
238 // add $0x10,%r11
239 // mov (%r11),%rbx
240 // cmp %rbx,%rax
241 // jne loop
242 // success:
243 // mov 0x8(%r11),%r11d
244 // mov (%r10,%r11,1),%rbx
245 // jmpq *0x60(%rbx)
246 // throw_icce:
247 // jmpq throw_ICCE_entry
209 } 248 }
210 249
211 int VtableStub::pd_code_alignment() { 250 int VtableStub::pd_code_alignment() {
212 return wordSize; 251 return wordSize;
213 } 252 }