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Target Description Macros
In addition to the file `MACHINE.md', a machine description includes
a C header file conventionally given the name `MACHINE.h'. This header
file defines numerous macros that convey the information about the
target machine that does not fit into the scheme of the `.md' file.
The file `tm.h' should be a link to `MACHINE.h'. The header file
`config.h' includes `tm.h' and most compiler source files include
- Controlling how the driver runs the compilation passes.
- Run-time Target
- Defining `-m' options like `-m68000' and `-m68020'.
- Storage Layout
- Defining sizes and alignments of data.
- Type Layout
- Defining sizes and properties of basic user data types.
- Naming and describing the hardware registers.
- Register Classes
- Defining the classes of hardware registers.
- Stack and Calling
- Defining which way the stack grows and by how much.
- Defining the varargs macros.
- Code set up at run time to enter a nested function.
- Library Calls
- Controlling how library routines are implicitly called.
- Addressing Modes
- Defining addressing modes valid for memory operands.
- Condition Code
- Defining how insns update the condition code.
- Defining relative costs of different operations.
- Dividing storage into text, data, and other sections.
- Macros for position independent code.
- Assembler Format
- Defining how to write insns and pseudo-ops to output.
- Debugging Info
- Defining the format of debugging output.
- Handling floating point for cross-compilers.
- Everything else.
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