gcc: Constraints

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1 6.45.3 Constraints for 'asm' Operands
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1 Here are specific details on what constraint letters you can use with
1 'asm' operands.  Constraints can say whether an operand may be in a
1 register, and which kinds of register; whether the operand can be a
1 memory reference, and which kinds of address; whether the operand may be
1 an immediate constant, and which possible values it may have.
1 Constraints can also require two operands to match.  Side-effects aren't
1 allowed in operands of inline 'asm', unless '<' or '>' constraints are
1 used, because there is no guarantee that the side effects will happen
1 exactly once in an instruction that can update the addressing register.
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Menu

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· Simple Constraints  Basic use of constraints.
· Multi-Alternative   When an insn has two alternative constraint-patterns.
· Modifiers           More precise control over effects of constraints.
· Machine Constraints Special constraints for some particular machines.
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