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comparison docs/CodeGenerator.rst @ 83:60c9769439b8

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LLVM 3.7
author Tatsuki IHA <e125716@ie.u-ryukyu.ac.jp>
date Wed, 18 Feb 2015 14:55:36 +0900
parents 54457678186b
children afa8332a0e37
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78:af83660cff7b 83:60c9769439b8
288 supported by the target. Descriptions define things like the mnemonic for 288 supported by the target. Descriptions define things like the mnemonic for
289 the opcode, the number of operands, the list of implicit register uses and defs, 289 the opcode, the number of operands, the list of implicit register uses and defs,
290 whether the instruction has certain target-independent properties (accesses 290 whether the instruction has certain target-independent properties (accesses
291 memory, is commutable, etc), and holds any target-specific flags. 291 memory, is commutable, etc), and holds any target-specific flags.
292 292
293 The ``TargetFrameInfo`` class 293 The ``TargetFrameLowering`` class
294 ----------------------------- 294 ---------------------------------
295 295
296 The ``TargetFrameInfo`` class is used to provide information about the stack 296 The ``TargetFrameLowering`` class is used to provide information about the stack
297 frame layout of the target. It holds the direction of stack growth, the known 297 frame layout of the target. It holds the direction of stack growth, the known
298 stack alignment on entry to each function, and the offset to the local area. 298 stack alignment on entry to each function, and the offset to the local area.
299 The offset to the local area is the offset from the stack pointer on function 299 The offset to the local area is the offset from the stack pointer on function
300 entry to the first location where function data (local variables, spill 300 entry to the first location where function data (local variables, spill
301 locations) can be stored. 301 locations) can be stored.
462 462
463 ;; X is in EAX, Y is in ECX 463 ;; X is in EAX, Y is in ECX
464 mov %EAX, %EDX 464 mov %EAX, %EDX
465 sar %EDX, 31 465 sar %EDX, 31
466 idiv %ECX 466 idiv %ECX
467 ret 467 ret
468 468
469 This approach is extremely general (if it can handle the X86 architecture, it 469 This approach is extremely general (if it can handle the X86 architecture, it
470 can handle anything!) and allows all of the target specific knowledge about the 470 can handle anything!) and allows all of the target specific knowledge about the
471 instruction stream to be isolated in the instruction selector. Note that 471 instruction stream to be isolated in the instruction selector. Note that
472 physical registers should have a short lifetime for good code generation, and 472 physical registers should have a short lifetime for good code generation, and
846 The ``-view-sunit-dags`` displays the Scheduler's dependency graph. This graph 846 The ``-view-sunit-dags`` displays the Scheduler's dependency graph. This graph
847 is based on the final SelectionDAG, with nodes that must be scheduled together 847 is based on the final SelectionDAG, with nodes that must be scheduled together
848 bundled into a single scheduling-unit node, and with immediate operands and 848 bundled into a single scheduling-unit node, and with immediate operands and
849 other nodes that aren't relevant for scheduling omitted. 849 other nodes that aren't relevant for scheduling omitted.
850 850
851 The option ``-filter-view-dags`` allows to select the name of the basic block
852 that you are interested to visualize and filters all the previous
853 ``view-*-dags`` options.
854
851 .. _Build initial DAG: 855 .. _Build initial DAG:
852 856
853 Initial SelectionDAG Construction 857 Initial SelectionDAG Construction
854 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 858 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
855 859