DIRECTORY
TargetArchitecture,
RuntimeError;

TargetArchitectureImpl: CEDAR PROGRAM
IMPORTS RuntimeError
EXPORTS TargetArchitecture
~ {

IsNullAddress: PUBLIC PROCEDURE [address: TargetArchitecture.Address] 
RETURNS [BOOLEAN] ~ {
isNullAddress: BOOLEAN ~ (address = TargetArchitecture.nullAddress);
RETURN [isNullAddress];
};

AddressFromDisplacement: PUBLIC PROCEDURE [
address: TargetArchitecture.Address, 
displacement: TargetArchitecture.Displacement]
RETURNS [TargetArchitecture.Address] ~ {
ordAddress: CARD32 ~ LOOPHOLE[address];
ordTarget: CARD32 ¬ 0;
displaced: TargetArchitecture.Address ¬ TargetArchitecture.nullAddress;

IF displacement >= 0
THEN {
absDisplacement: CARD32 ~ displacement;

IF LAST[CARD32] - ordAddress < absDisplacement THEN {
ERROR RuntimeError.BoundsFault;
};
ordTarget ¬ ordAddress + absDisplacement;
}
ELSE {
absDisplacement: CARD32 ~ -displacement;

IF ordAddress < absDisplacement THEN {
ERROR RuntimeError.BoundsFault;
};
ordTarget ¬ ordAddress - absDisplacement;
};
displaced ¬ LOOPHOLE[ordTarget];
RETURN [displaced];
};

DisplacementFromAddresses: PUBLIC PROCEDURE [
here: TargetArchitecture.Address, 
there: TargetArchitecture.Address] RETURNS [TargetArchitecture.Displacement] ~ {
ordHere: CARD32 ~ LOOPHOLE[here];
ordThere: CARD32 ~ LOOPHOLE[there];
displacement: TargetArchitecture.Displacement ~ 
IF ordThere >= ordHere
THEN ordThere - ordHere
ELSE -(ordHere - ordThere);

RETURN [displacement];
};

NextInstruction: PUBLIC PROCEDURE [pc: TargetArchitecture.Address] 
RETURNS [TargetArchitecture.Address] ~ {
nextAddress: TargetArchitecture.Address ~ AddressFromDisplacement[
address: pc, displacement: +BYTES[TargetArchitecture.Instruction]];

RETURN [nextAddress];
};

PrevInstruction: PUBLIC PROCEDURE [pc: TargetArchitecture.Address] 
RETURNS [TargetArchitecture.Address] ~ {
prevAddress: TargetArchitecture.Address ~ AddressFromDisplacement[
address: pc, displacement: -BYTES[TargetArchitecture.Instruction]];

RETURN [prevAddress];
};

InstructionFromContents: PUBLIC PROCEDURE [contents: TargetArchitecture.Contents] 
RETURNS [TargetArchitecture.Instruction] ~ {
instruction: TargetArchitecture.Instruction ~ LOOPHOLE[contents];

RETURN [instruction];
};

ContentsFromInstruction: PUBLIC PROCEDURE [instruction: TargetArchitecture.Instruction] 
RETURNS [TargetArchitecture.Contents] ~ {
contents: TargetArchitecture.Contents ~ LOOPHOLE[instruction];

RETURN [contents];
};

}.
   ,  
TargetArchitectureImpl.mesa
Copyright Ó 1989, 1991 by Xerox Corporation.  All rights reserved.
Peter B. Kessler, September 1, 1989 4:55:02 pm PDT

Check first for possible overflow.
Check first for possible underflow.
See section 2.5.1.1 of the Mesa manual for rules on unsigned arithmetic.

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