在上一篇文章介绍了一种加IACA标记的方法，但使用还是很麻烦，所以我尝试修改pony编译器，直接增加了IACA支持，目前代码在iaca分支。
使用方法
因为还没发PR到上游，所以要自己克隆编译。
git clone https://github.com/oraoto/ponyc.git
cd ponyc
git checkout iaca然后安装官方的编译步骤编译就好了，通常就是一句make。
在需要添加IACA标记的代码加上IACA.start()和IACA.stop()就可以了。以pony-websocket里的代码为例：
while (i + 4) < size doIACA.start()p(i)? = p(i)? xor m1p(i + 1)? = p(i + 1)? xor m2p(i + 2)? = p(i + 2)? xor m3p(i + 3)? = p(i + 3)? xor m4i = i + 4
end
IACA.stop()编译后就可以用iaca进行分析了：
$ iaca ./echo-server.exeF:\build > iaca .\echo-server.exe
Intel(R) Architecture Code Analyzer Version - v3.0-28-g1ba2cbb build date: 2017-10-23;17:30:24
Analyzed File - .\echo-server.exe
Binary Format - 64Bit
Architecture - SKL
Analysis Type - ThroughputThroughput Analysis Report
--------------------------
Block Throughput: 6.74 Cycles Throughput Bottleneck: Dependency chains
Loop Count: 22
Port Binding In Cycles Per Iteration:
--------------------------------------------------------------------------------------------------
| Port | 0 - DV | 1 | 2 - D | 3 - D | 4 | 5 | 6 | 7 |
--------------------------------------------------------------------------------------------------
| Cycles | 2.5 0.0 | 2.5 | 4.0 4.0 | 4.0 4.0 | 4.0 | 2.5 | 2.5 | 0.0 |
--------------------------------------------------------------------------------------------------DV - Divider pipe (on port 0)
D - Data fetch pipe (on ports 2 and 3)
F - Macro Fusion with the previous instruction occurred
* - instruction micro-ops not bound to a port
^ - Micro Fusion occurred
# - ESP Tracking sync uop was issued
@ - SSE instruction followed an AVX256/AVX512 instruction, dozens of cycles penalty is expected
X - instruction not supported, was not accounted in Analysis| Num Of | Ports pressure in cycles | |
| Uops | 0 - DV | 1 | 2 - D | 3 - D | 4 | 5 | 6 | 7 |
-----------------------------------------------------------------------------------------
| 1* | | | | | | | | | cmp rax, rbx
| 0*F | | | | | | | | | jbe 0x95
| 4 | | 0.5 | 1.0 1.0 | 1.0 1.0 | 1.0 | | 0.5 | | xor byte ptr [rdi+rbx*1], r8b
| 1 | | 0.5 | | | | 0.5 | | | lea rsi, ptr [rbx+0x1]
| 1* | | | | | | | | | cmp rax, rsi
| 0*F | | | | | | | | | jbe 0x8b
| 4 | 0.5 | | 1.0 1.0 | 1.0 1.0 | 1.0 | | 0.5 | | xor byte ptr [rdi+rbx*1+0x1], r9b
| 1 | 0.5 | | | | | 0.5 | | | add rsi, 0x1
| 1* | | | | | | | | | cmp rax, rsi
| 0*F | | | | | | | | | jbe 0x80
| 4 | | 0.5 | 1.0 1.0 | 1.0 1.0 | 1.0 | | 0.5 | | xor byte ptr [rdi+rbx*1+0x2], r10b
| 1 | 0.5 | | | | | 0.5 | | | add rsi, 0x1
| 1* | | | | | | | | | cmp rax, rsi
| 0*F | | | | | | | | | jbe 0x75
| 4 | | 0.5 | 1.0 1.0 | 1.0 1.0 | 1.0 | | 0.5 | | xor byte ptr [rdi+rbx*1+0x3], r11b
| 1 | | 0.5 | | | | 0.5 | | | lea rdx, ptr [rsi+0x5]
| 1 | 0.5 | | | | | | 0.5 | | add rsi, 0x1
| 1* | | | | | | | | | cmp rdx, rax
| 0*F | | | | | | | | | jb 0xffffffffffffffab
| 1 | 0.5 | | | | | 0.5 | | | add rbx, 0x4
Total Num Of Uops: 27实现方式
pony的builtin包里，有些代码是这样的：
fun _apply(i: USize): this->A =>compile_intrinsicfun ref _update(i: USize, value: A!): A^ =>compile_intrinsicfun _offset(n: USize): this->Pointer[A] =>compile_intrinsic函数体只有一句compile_intrinsic，这些函数编译器内置的，可以直接生成代码。所以我直接在builtin包里加了
primitive IACAfun start(): None => compile_intrinsicfun stop(): None => compile_intrinsic这时编译是不通过的，因为编译器还不知道怎样编译这两个函数，所以要在编译器里“注册”，这里只要参考Platform包的处理就可以了。
实际生成代码的方法：
static void iaca_start(compile_t* c, reach_type_t* t, token_id cap)
{FIND_METHOD("start", cap);compile_type_t* t_result = (compile_type_t*)m->result->c_type;start_function(c, t, m, t_result->use_type, &c_t->use_type, 1);LLVMAddFunctionAttr(c_m->func, LLVMAlwaysInlineAttribute);LLVMTypeRef void_fn = LLVMFunctionType(c->void_type, NULL, 0, false);LLVMValueRef asmstr = LLVMConstInlineAsm(void_fn,".byte 0xbb, 0x6f, 0, 0, 0, 0x64, 0x67, 0x90", "", true, false);LLVMValueRef call = LLVMBuildCall(c->builder, asmstr, NULL, 0, "");LLVMBuildRet(c->builder, t_result->instance);codegen_finishfun(c);
}就是是生成一句inline asm的LLVM IR。不经优化生成的IR是这样的：
while_body: ; preds = %invoke13, %while_init%28 = call fastcc %IACA* @IACA_val_create_o(%IACA* @IACA_Inst), !dbg !5828, !pony.newcall !3%29 = call fastcc %None* @IACA_val_start_o(%IACA* %28), !dbg !5830; Function Attrs: alwaysinline
define fastcc %None* @IACA_val_start_o(%IACA* noalias readonly dereferenceable(8)) unnamed_addr #7 !pony.abi !3 {
entry:call void asm sideeffect ".byte 0xbb, 0x6f, 0, 0, 0, 0x64, 0x67, 0x90", ""()ret %None* @None_Inst
}没错，生成的是个函数调用，所以我们依赖于优化把这个函数内联到调用点，优化的结果是：
; <label>:38: ; preds = %35, %67%39 = phi i64 [ %71, %67 ], [ 0, %35 ]tail call void asm sideeffect ".byte 0xbb, 0x6f, 0, 0, 0, 0x64, 0x67, 0x90", ""() #2%40 = icmp ugt i64 %4, %39br i1 %40, label %43, label %41这就是我们要的。
目前的不足是，因为还是生成了函数的代码，iaca有时会分析错位置，会出现下面的结果：
| Num Of | Ports pressure in cycles | |
| Uops | 0 - DV | 1 | 2 - D | 3 - D | 4 | 5 | 6 | 7 |
-----------------------------------------------------------------------------------------
| 1 | | | | | | 1.0 | | | lea rax, ptr [rip+0x71a8]
| 3^# | | | 1.0 1.0 | | | | 0.1 | | ret
| 1 | 0.4 | | | | | | 0.6 | | mov ebx, 0x6f
| 1 | 0.6 | | | | | | 0.4 | | addr32 nop
| 1 | | 1.0 | | | | | | | lea rax, ptr [rip+0x71a8]
| 3^ | | | | 1.0 1.0 | | | | | ret
Total Num Of Uops: 10编译结果居然不是确定的？遇到这种情况，现在只能再编译，直到出现正确的结果。
