gccint: RTL Declarations

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1 14.14 Declarations
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1 Declaration expression codes do not represent arithmetic operations but
1 rather state assertions about their operands.
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1 '(strict_low_part (subreg:M (reg:N R) 0))'
1      This expression code is used in only one context: as the
1      destination operand of a 'set' expression.  In addition, the
1      operand of this expression must be a non-paradoxical 'subreg'
1      expression.
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1      The presence of 'strict_low_part' says that the part of the
1      register which is meaningful in mode N, but is not part of mode M,
1      is not to be altered.  Normally, an assignment to such a subreg is
1      allowed to have undefined effects on the rest of the register when
1      M is smaller than 'REGMODE_NATURAL_SIZE (N)'.
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