t30依赖GraphRoot,故t30是第一个调度的节点,将调度结果存入到一个数组中(这里使用Sequence表示),同时将t30从图8-6中移除,并更新t30依赖节点的入度,即将t45入度减1。此时,t45的局部依赖图如图8-7所示。 图8- 7 t30调度后的局部依赖图 此时,Sequence中的调度结果为t30。 第2步,处理具有Glue属性的节点序列。 接...
寄存器。节点t1、t3、t7各表示一个寄存器;其中t7的寄存器是固定用于传递函数返回值的,t8 CopyToReg节点将t5 add的结果存入t7表示的寄存器内;而t1和t3两个寄存器用于传入本函数的两个入参,t2和t4两个CopyFromReg节点负责复制它们并传递给t5 add节点进行运算。像图中这种情况,t2和t4在后期会被优化掉,因为t1和t3...
分析别名寄存器. 在LLVM中物理寄存器不同与虚拟寄存器, 不同类型的虚拟寄存器在preRA阶段存在COPY/PHI/REG_SEQUENCE等方式转换寄存器类型, 但postRA阶段对应的伪指令被消除, 判断寄存器分类时需要考虑子集/超集. 各式各样的寄存器标记. 类似1的原因, 在postRA阶段寄存器标记远远多于preRA阶段, 不同的寄存器标签影响寄存器...
(\c) escape sequences 忽略C风格(\ c)转义序列 --no_warn Turn off Warning messages 关闭警告信息 -g Output debugging tables 输出调试表 --apcs /<quals> Make pre-definitions to match the chosen procedure-call standard 进行预定义以匹配选择的程序调用标准 --checkreglist Warn about out of order ...
}/// Return how this operation should be treated: either it is legal, needs to/// be promoted to a larger size, needs to be expanded to some other code/// sequence, or the target has a custom expander for it.LegalizeActiongetOperationAction(unsignedOp, EVT VT)const{if(VT.isExtended(...
def FPRegs : RegisterClass<"SP", [f32], 32, (sequence "F%u", 0,31)>; 1. 这里定义了一组32个从F0-F31 单精度浮点类型的寄存器。 def DFPRegs : RegisterClass<"SP", [f64], 64, (add D0, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12, D13, D14, D15)>...
; ... LLVM IR sequence for the sub instruction 3.2控制流伪代码函数生成,为什么不用ir是因为ir通过块标签跳转而不是像汇编一样通过地址 Control-flow-related pseudo functions are generated. ; void (i<architecture_size> target_address) declare void @__pseudo_call(i32) ...
On some targets this flag has no effect because the standard calling sequence always uses a frame pointer, so it cannot be omitted. Note that-fno-omit-frame-pointerdoesn’t guarantee the frame pointer is used in all functions. Several targets always omit the frame pointer in leaf functions. ...
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LLVM笔记（12）-指令选择（四）legalize 本节介绍指令选择中legalize的概念, 为中端IR精确匹配机器指令需要同时检查操作符与操作数, 在正式指令选择前对不合法的操作符或操作数作出转换的过程即legalize.通常情况下给定⼀个后端架构其⽀持的指令集:1. 不⼀定能⽀持表达所有中端IR的操作. ⼀个显⽽易见的...