使用-XX:+UnlockDiagnosticVMOptions -XX:+PrintInterpreter -XX:+LogCompilation -XX:LogFile=file.log保存结果到文件，可以查看生成的这些例程。
随便举个例子，模板解释器特殊处理java.lang.Math里的很多数学函数，使用它们不需要建立通常意义的java栈帧，且使用sse指令可以得到极大的性能提升：
// hotspot\src\cpu\x86\vm\templateInterpreterGenerator_x86_64.cpp
address TemplateInterpreterGenerator::generate_math_entry(AbstractInterpreter::MethodKind kind) {
// rbx,: Method*
// rcx: scratrch
// r13: sender sp
if (!InlineIntrinsics) return NULL; // Generate a vanilla entry
address entry_point = __ pc();
if (kind == Interpreter::java_lang_math_fmaD) {
if (!UseFMA) {
return NULL; // Generate a vanilla entry
}
__ movdbl(xmm0, Address(rsp, wordSize));
__ movdbl(xmm1, Address(rsp, 3 * wordSize));
__ movdbl(xmm2, Address(rsp, 5 * wordSize));
__ fmad(xmm0, xmm1, xmm2, xmm0);
} else if (kind == Interpreter::java_lang_math_fmaF) {
if (!UseFMA) {
return NULL; // Generate a vanilla entry
}
__ movflt(xmm0, Address(rsp, wordSize));
__ movflt(xmm1, Address(rsp, 2 * wordSize));
__ movflt(xmm2, Address(rsp, 3 * wordSize));
__ fmaf(xmm0, xmm1, xmm2, xmm0);
} else if (kind == Interpreter::java_lang_math_sqrt) {
__ sqrtsd(xmm0, Address(rsp, wordSize));
} else if (kind == Interpreter::java_lang_math_exp) {
__ movdbl(xmm0, Address(rsp, wordSize));
if (StubRoutines::dexp() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dexp())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dexp));
}
} else if (kind == Interpreter::java_lang_math_log) {
__ movdbl(xmm0, Address(rsp, wordSize));
if (StubRoutines::dlog() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dlog())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dlog));
}
} else if (kind == Interpreter::java_lang_math_log10) {
__ movdbl(xmm0, Address(rsp, wordSize));
if (StubRoutines::dlog10() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dlog10())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dlog10));
}
} else if (kind == Interpreter::java_lang_math_sin) {
__ movdbl(xmm0, Address(rsp, wordSize));
if (StubRoutines::dsin() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dsin())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dsin));
}
} else if (kind == Interpreter::java_lang_math_cos) {
__ movdbl(xmm0, Address(rsp, wordSize));
if (StubRoutines::dcos() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dcos())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dcos));
}
} else if (kind == Interpreter::java_lang_math_pow) {
__ movdbl(xmm1, Address(rsp, wordSize));
__ movdbl(xmm0, Address(rsp, 3 * wordSize));
if (StubRoutines::dpow() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dpow())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dpow));
}
} else if (kind == Interpreter::java_lang_math_tan) {
__ movdbl(xmm0, Address(rsp, wordSize));
if (StubRoutines::dtan() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dtan())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dtan));
}
} else {
__ fld_d(Address(rsp, wordSize));
switch (kind) {
case Interpreter::java_lang_math_abs:
__ fabs();
break;
default:
ShouldNotReachHere();
}
__ subptr(rsp, 2*wordSize);
// Round to 64bit precision
__ fstp_d(Address(rsp, 0));
__ movdbl(xmm0, Address(rsp, 0));
__ addptr(rsp, 2*wordSize);
}
__ pop(rax);
__ mov(rsp, r13);
__ jmp(rax);
return entry_point;
}
我们关注java.lang.math.Pow()方法，加上-XX:+PrintInterpreter查看生成的例程：
else if (kind == Interpreter::java_lang_math_pow) {
__ movdbl(xmm1, Address(rsp, wordSize));
__ movdbl(xmm0, Address(rsp, 3 * wordSize));
if (StubRoutines::dpow() != NULL) {
__ call(RuntimeAddress(CAST_FROM_FN_PTR(address, StubRoutines::dpow())));
} else {
__ call_VM_leaf0(CAST_FROM_FN_PTR(address, SharedRuntime::dpow));
}
}
----------------------------------------------------------------------
method entry point (kind = java_lang_math_pow) [0x000001bcb62feaa0, 0x000001bcb62feac0] 32 bytes
0x000001bcb62feaa0: vmovsd 0x8(%rsp),%xmm1
0x000001bcb62feaa6: vmovsd 0x18(%rsp),%xmm0
0x000001bcb62feaac: callq 0x000001bcb62f19d0
0x000001bcb62feab1: pop %rax
0x000001bcb62feab2: mov %r13,%rsp
0x000001bcb62feab5: jmpq *%rax
0x000001bcb62feab7: nop
0x000001bcb62feab8: add %al,(%rax)
0x000001bcb62feaba: add %al,(%rax)
0x000001bcb62feabc: add %al,(%rax)
0x000001bcb62feabe: add %al,(%rax)
callq会调用hotspot\src\cpu\x86\vm\stubGenerator_x86_64.cpp的address generate_libmPow()，感兴趣的可以去看一下，这里就不展开了。
2.字节码的解释执行
