hexagon/idef-parser/README.rst

1 Hexagon ISA instruction definitions to tinycode generator compiler
11 example. Let's start by one of the simplest Hexagon instruction: the ``add``.
13 The ISA description language represents the ``add`` instruction as
45 Let's begin by describing the input code. The ``add`` instruction is associated
47 variants of the same instruction, and expresses the class to which the
48 instruction belongs, in this case ``A2`` corresponds to the Hexagon
49 ``ALU32/ALU`` instruction subclass.
51 After the instruction identifier, we have a series of parameters that represents
62 Let's now observe the actual instruction description code, in this case:
109 instruction semantics in ``semantics_generated.pyinc`` that we need to consider.
116 which takes instruction semantics in ``semantics_generated.pyinc`` to C-like
118 ``J2_jumpr`` instruction which jumps to an address stored in a register
119 argument. This is instruction is defined as
186 The grammar describes the whole file which contains the Hexagon instruction
188 list of instructions, each instruction is represented by the following grammar
193    instruction : INAME arguments code
224 With this initial portion of the grammar we are defining the instruction, its'
242 bracket-enclosed list of statements, a ``';'``, which is a ``nop`` instruction,
395 are handled using the conditional move tinycode instruction
414 therefore the instruction compilation could easily be parallelized in the
450 Implementing an instruction goes through several sequential steps, here are some
451 suggestions to make each instruction proceed to the next step.
455    Means that the parsing of the input code relative to that instruction failed,
463    This instruction class contains all the instructions which are emitted but
471    These instruction generate valid tinycode generator code, which however fail
474    generator instruction and at the generated tinycode itself. Tip: handle the
476    instruction, thus will require less execution trace navigation. If a
485    This is the final goal for each instruction, meaning that the instruction
491 where the instruction pass the test, and run it with the following command:
506 incorrectly emitted tinycode generator for a single instruction.
509 instruction,
525 ``A2_add`` instruction is so ubiquitous. As a result, pretty much all tests will
630 Therefore, we are either dealing with an correct load instruction
635 tinycode for the Hexagon ``add`` instruction