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Diffstat (limited to 'docs/CodeGenerator.rst')
| -rw-r--r-- | docs/CodeGenerator.rst | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/docs/CodeGenerator.rst b/docs/CodeGenerator.rst index b0a1059..75d40db 100644 --- a/docs/CodeGenerator.rst +++ b/docs/CodeGenerator.rst @@ -464,7 +464,7 @@ code: mov %EAX, %EDX sar %EDX, 31 idiv %ECX - ret + ret This approach is extremely general (if it can handle the X86 architecture, it can handle anything!) and allows all of the target specific knowledge about the @@ -848,6 +848,10 @@ is based on the final SelectionDAG, with nodes that must be scheduled together bundled into a single scheduling-unit node, and with immediate operands and other nodes that aren't relevant for scheduling omitted. +The option ``-filter-view-dags`` allows to select the name of the basic block +that you are interested to visualize and filters all the previous +``view-*-dags`` options. + .. _Build initial DAG: Initial SelectionDAG Construction @@ -1336,7 +1340,7 @@ found before being stored or after being reloaded. If the indirect strategy is used, after all the virtual registers have been mapped to physical registers or stack slots, it is necessary to use a spiller object to place load and store instructions in the code. Every virtual that has -been mapped to a stack slot will be stored to memory after been defined and will +been mapped to a stack slot will be stored to memory after being defined and will be loaded before being used. The implementation of the spiller tries to recycle load/store instructions, avoiding unnecessary instructions. For an example of how to invoke the spiller, see ``RegAllocLinearScan::runOnMachineFunction`` in @@ -1349,7 +1353,7 @@ With very rare exceptions (e.g., function calls), the LLVM machine code instructions are three address instructions. That is, each instruction is expected to define at most one register, and to use at most two registers. However, some architectures use two address instructions. In this case, the -defined register is also one of the used register. For instance, an instruction +defined register is also one of the used registers. For instance, an instruction such as ``ADD %EAX, %EBX``, in X86 is actually equivalent to ``%EAX = %EAX + %EBX``. @@ -1574,7 +1578,7 @@ three important things that you have to implement for your target: correspond to. The MCInsts that are generated by this are fed into the instruction printer or the encoder. -Finally, at your choosing, you can also implement an subclass of MCCodeEmitter +Finally, at your choosing, you can also implement a subclass of MCCodeEmitter which lowers MCInst's into machine code bytes and relocations. This is important if you want to support direct .o file emission, or would like to implement an assembler for your target. |