as: Xtensa Directives

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1 9.55.5 Directives
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1 The Xtensa assembler supports a region-based directive syntax:
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1          .begin DIRECTIVE [OPTIONS]
1          ...
1          .end DIRECTIVE
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1    All the Xtensa-specific directives that apply to a region of code use
1 this syntax.
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1    The directive applies to code between the '.begin' and the '.end'.
1 The state of the option after the '.end' reverts to what it was before
1 the '.begin'.  A nested '.begin'/'.end' region can further change the
1 state of the directive without having to be aware of its outer state.
1 For example, consider:
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1          .begin no-transform
1      L:  add a0, a1, a2
1          .begin transform
1      M:  add a0, a1, a2
1          .end transform
1      N:  add a0, a1, a2
1          .end no-transform
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1    The 'ADD' opcodes at 'L' and 'N' in the outer 'no-transform' region
1 both result in 'ADD' machine instructions, but the assembler selects an
1 'ADD.N' instruction for the 'ADD' at 'M' in the inner 'transform'
1 region.
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1    The advantage of this style is that it works well inside macros which
1 can preserve the context of their callers.
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1    The following directives are available:

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· Schedule Directive         Enable instruction scheduling.
· Longcalls Directive        Use Indirect Calls for Greater Range.
· Transform Directive        Disable All Assembler Transformations.
· Literal Directive          Intermix Literals with Instructions.
· Literal Position Directive Specify Inline Literal Pool Locations.
· Literal Prefix Directive   Specify Literal Section Name Prefix.
· Absolute Literals Directive Control PC-Relative vs. Absolute Literals.
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