1 JIT入口开关
standard_planner
...
...
result->jitFlags = PGJIT_NONE;
if (jit_enabled && jit_above_cost >= 0 &&
top_plan->total_cost > jit_above_cost)
{
result->jitFlags |= PGJIT_PERFORM;
/*
* Decide how much effort should be put into generating better code.
*/
if (jit_optimize_above_cost >= 0 &&
top_plan->total_cost > jit_optimize_above_cost)
result->jitFlags |= PGJIT_OPT3;
if (jit_inline_above_cost >= 0 &&
top_plan->total_cost > jit_inline_above_cost)
result->jitFlags |= PGJIT_INLINE;
/*
* Decide which operations should be JITed.
*/
if (jit_expressions)
result->jitFlags |= PGJIT_EXPR;
if (jit_tuple_deforming)
result->jitFlags |= PGJIT_DEFORM;
}
jit_compile_expr_39">2 从表达式堆栈进入JIT逻辑jit_compile_expr
《Postgresql源码（113）表达式JIT计算简单分析》
#0 jit_compile_expr (state=0x1deae18) at jit.c:180
#1 0x000000000071fa6b in ExecReadyExpr (state=0x1deae18) at execExpr.c:874
#2 0x000000000071e60b in ExecInitExpr (node=0x1dfabb8, parent=0x0) at execExpr.c:152
#3 0x00000000008b3395 in evaluate_expr (expr=0x1dfabb8, result_type=23, result_typmod=-1, result_collation=0) at clauses.c:4892
#4 0x00000000008b26f8 in evaluate_function (funcid=1397, result_type=23, result_typmod=-1, result_collid=0, input_collid=0, args=0x1dfab68, funcvariadic=false, func_tuple=0x7fd9588871a8, context=0x7ffdd8867f20) at clauses.c:4409
...
jit_compile_exprllvmjitso_50">3 jit_compile_expr初始化加载llvmjit.so
jit_compile_expr
provider_init
load_external_function(path, "_PG_jit_provider_init", true, NULL)
dlopen动态加载llvmjit.so，并调用so中的_PG_jit_provider_init初始化：
void
_PG_jit_provider_init(JitProviderCallbacks *cb)
{
cb->reset_after_error = llvm_reset_after_error;
cb->release_context = llvm_release_context;
cb->compile_expr = llvm_compile_expr;
}
为provider配置入口函数：
typedef struct JitProviderCallbacks JitProviderCallbacks;
struct JitProviderCallbacks
{
JitProviderResetAfterErrorCB reset_after_error;
JitProviderReleaseContextCB release_context;
JitProviderCompileExprCB compile_expr;
};
static JitProviderCallbacks provider;
jit_compile_expr继续调用hook：provider.compile_expr进入llvm逻辑：
jit_compile_expr
provider_init
provider.compile_expr(state) -> llvm_compile_expr
llvm_compile_exprllvm_create_context_86">4 llvm_compile_expr执行初始化llvm_create_context
llvm_create_context初始化生成LLVMJitContext结构：
typedef struct JitContext
{
/* see PGJIT_* above */
int flags;
ResourceOwner resowner;
JitInstrumentation instr;
} JitContext;
typedef struct LLVMJitContext
{
JitContext base; // 上面的JIT FLAG、ResourceOwner
size_t module_generation; // 当前context存了几个Module？
LLVMModuleRef module; // 当前正在使用的module
bool compiled; // 已经编译过了？
List *handles; // 所有挂在当前context下的module
} LLVMJitContext;
llvm_create_context初始化流程
llvm_create_context
llvm_session_initialize
【库函数】LLVMInitializeNativeTarget
【库函数】LLVMInitializeNativeAsmPrinter
【库函数】LLVMInitializeNativeAsmParser
【库函数】LLVMContextSetOpaquePointers
读取llvmjit_types.bc中需要的类型、函数签名：llvm_create_types
LLVMCreateMemoryBufferWithContentsOfFile
LLVMParseBitcode2
LLVMDisposeMemoryBuffer
【库函数】LLVMGetTargetFromTriple
...
【库函数】LLVMLoadLibraryPermanently
llvm_ts_context = LLVMOrcCreateNewThreadSafeContext
llvm_opt0_orc = llvm_create_jit_instance
【库函数】若干
传入机器信息，构造LLVMJIT环境
【库函数】若干
LLVMOrcJITTargetMachineBuilderCreateFromTargetMachine
【库函数】若干
LLVMOrcCreateLLJIT
llvm_opt3_orc = llvm_create_jit_instance
【库函数】若干
传入机器信息，构造LLVMJIT环境
【库函数】若干
LLVMOrcJITTargetMachineBuilderCreateFromTargetMachine
【库函数】若干
LLVMOrcCreateLLJIT
ResourceOwnerEnlargeJIT
/*
* Load triple & layout from clang emitted file so we're guaranteed to be
* compatible.
*/
llvm_triple = pstrdup(LLVMGetTarget(llvm_types_module));
llvm_layout = pstrdup(LLVMGetDataLayoutStr(llvm_types_module));
TypeSizeT = llvm_pg_var_type("TypeSizeT");
TypeParamBool = load_return_type(llvm_types_module, "FunctionReturningBool");
TypeStorageBool = llvm_pg_var_type("TypeStorageBool");
TypePGFunction = llvm_pg_var_type("TypePGFunction");
StructNullableDatum = llvm_pg_var_type("StructNullableDatum");
StructExprContext = llvm_pg_var_type("StructExprContext");
StructExprEvalStep = llvm_pg_var_type("StructExprEvalStep");
StructExprState = llvm_pg_var_type("StructExprState");
StructFunctionCallInfoData = llvm_pg_var_type("StructFunctionCallInfoData");
StructMemoryContextData = llvm_pg_var_type("StructMemoryContextData");
StructTupleTableSlot = llvm_pg_var_type("StructTupleTableSlot");
StructHeapTupleTableSlot = llvm_pg_var_type("StructHeapTupleTableSlot");
StructMinimalTupleTableSlot = llvm_pg_var_type("StructMinimalTupleTableSlot");
StructHeapTupleData = llvm_pg_var_type("StructHeapTupleData");
StructTupleDescData = llvm_pg_var_type("StructTupleDescData");
StructAggState = llvm_pg_var_type("StructAggState");
StructAggStatePerGroupData = llvm_pg_var_type("StructAggStatePerGroupData");
StructAggStatePerTransData = llvm_pg_var_type("StructAggStatePerTransData");
AttributeTemplate = LLVMGetNamedFunction(llvm_types_module, "AttributeTemplate");
读取到的所有类型、函数指针等记录在全局变量llvm_types_module中，用llvm_pg_var_type等函数调用LLVM库函数转换为LLVM能识别的类型、函数。
llvm_compile_exprmodule_180">5 llvm_compile_expr创建module
创建Module需要的llvm_triple、llvm_layout都来自llvm_create_types函数，读取llvmjit_types.bc拿到的信息。
LLVMModuleRef
llvm_mutable_module(LLVMJitContext *context)
{
llvm_assert_in_fatal_section();
/*
* If there's no in-progress module, create a new one.
*/
if (!context->module)
{
context->compiled = false;
context->module_generation = llvm_generation++;
context->module = LLVMModuleCreateWithName("pg");
LLVMSetTarget(context->module, llvm_triple);
LLVMSetDataLayout(context->module, llvm_layout);
}
return context->module;
}
llvm_compile_exprmodule_204">6 llvm_compile_expr新增函数到module中
llvm_compile_expr
新增函数到module
eval_fn = LLVMAddFunction(mod, funcname,
llvm_pg_var_func_type("TypeExprStateEvalFunc"));
函数中加BB
entry = LLVMAppendBasicBlock(eval_fn, "entry");
按表达式分支逻辑为BB添加代码
case EEOP_FUNCEXPR_STRICT:
{
FunctionCallInfo fcinfo = op->d.func.fcinfo_data;
LLVMValueRef v_fcinfo_isnull;
LLVMValueRef v_retval;
if (opcode == EEOP_FUNCEXPR_STRICT)
{
LLVMBasicBlockRef b_nonull;
LLVMBasicBlockRef *b_checkargnulls;
LLVMValueRef v_fcinfo;
/*
* Block for the actual function call, if args are
* non-NULL.
*/
b_nonull = l_bb_before_v(opblocks[opno + 1],
"b.%d.no-null-args", opno);
/* should make sure they're optimized beforehand */
if (op->d.func.nargs == 0)
elog(ERROR, "argumentless strict functions are pointless");
v_fcinfo =
l_ptr_const(fcinfo, l_ptr(StructFunctionCallInfoData));
/*
* set resnull to true, if the function is actually
* called, it'll be reset
*/
LLVMBuildStore(b, l_sbool_const(1), v_resnullp);
/* create blocks for checking args, one for each */
b_checkargnulls =
palloc(sizeof(LLVMBasicBlockRef *) * op->d.func.nargs);
for (int argno = 0; argno < op->d.func.nargs; argno++)
b_checkargnulls[argno] =
l_bb_before_v(b_nonull, "b.%d.isnull.%d", opno,
argno);
/* jump to check of first argument */
LLVMBuildBr(b, b_checkargnulls[0]);
/* check each arg for NULLness */
for (int argno = 0; argno < op->d.func.nargs; argno++)
{
LLVMValueRef v_argisnull;
LLVMBasicBlockRef b_argnotnull;
LLVMPositionBuilderAtEnd(b, b_checkargnulls[argno]);
/*
* Compute block to jump to if argument is not
* null.
*/
if (argno + 1 == op->d.func.nargs)
b_argnotnull = b_nonull;
else
b_argnotnull = b_checkargnulls[argno + 1];
/* and finally load & check NULLness of arg */
v_argisnull = l_funcnull(b, v_fcinfo, argno);
LLVMBuildCondBr(b,
LLVMBuildICmp(b, LLVMIntEQ,
v_argisnull,
l_sbool_const(1),
""),
opblocks[opno + 1],
b_argnotnull);
}
LLVMPositionBuilderAtEnd(b, b_nonull);
}
v_retval = BuildV1Call(context, b, mod, fcinfo,
&v_fcinfo_isnull);
LLVMBuildStore(b, v_retval, v_resvaluep);
LLVMBuildStore(b, v_fcinfo_isnull, v_resnullp);
LLVMBuildBr(b, opblocks[opno + 1]);
break;
}
7 （核心步骤）ExecRunCompiledExpr对module进行编译、优化、执行
ExecRunCompiledExpr找到jit函数并执行，惰性编译、优化。
ExecRunCompiledExpr
llvm_get_function
重要：llvm_compile_module
LLVMOrcLLJITLookup
在找函数执行时，编译这一步是核心逻辑，编译会对上面逻辑进行优化处理：
llvm_compile_module
llvm_inline
llvm_optimize_module
优化一：llvm_inline
、llvm_build_inline_plan会查询module里面的function，到函数目录查找对应的bc文件，并加载bc文件中函数的逻辑（增加LLVM编译后，所有源码文件都会用clang额外生成一个bc文件，提供给inline使用）。function_inlinable函数会检查当前函数引用的其他函数时候能inline。
优化二：llvm_optimize_module
将IR过一遍PASS，下一篇继续分析后面的流程。
