DJumps.mesa
Copyright © 1985 by Xerox Corporation. All rights reserved.
Sweet, March 20, 1979 4:53 PM
Satterthwaite, November 2, 1982 3:52 pm
Russ Atkinson (RRA) March 6, 1985 11:15:13 pm PST
DIRECTORY
Alloc USING [Base, Notifier],
Code USING [codeptr],
CodeDefs USING [Base, CCIndex, CCNull, codeType, JumpCCIndex, JumpType, RelativePC],
OpCodeParams USING [MaxBBJumps, MaxFBJumps, MaxFIAJumps, MaxFICJumps],
P5F USING [CodeJumpDist, StartIndex];
DJumps:
PROGRAM
IMPORTS CPtr: Code, P5F
EXPORTS CodeDefs, P5F = BEGIN OPEN OpCodeParams, CodeDefs;
cb: CodeDefs.Base; -- code base (local copy)
DJumpsNotify:
PUBLIC Alloc.Notifier =
BEGIN -- called by allocator whenever table area is repacked
cb ← base[codeType];
END;
BindJump:
PUBLIC
PROC [min, max:
INTEGER, c: JumpCCIndex]
RETURNS [bindable: BOOL ← TRUE] =
BEGIN -- compute size of jump instruction(s)
max and min are counts of the number of bytes between the
jump and the label.
t: JumpType = cb[c].jtype;
js: [0..7];
IF t = JumpC
THEN
BEGIN -- "bound" by OutBinary
cb[c].fixedup ← TRUE;
cb[c].completed ← TRUE;
RETURN
END;
IF ~cb[c].forward THEN BEGIN max ← -max; min ← -min END;
SELECT t
FROM
Jump, JumpA =>
IF max IN [1..MaxFIAJumps] THEN js ← 1
ELSE IF max IN (MaxFIAJumps..MaxFBJumps-2] AND min > MaxFIAJumps THEN js ← 2
ELSE IF max IN [-MaxBBJumps..0] THEN js ← 2
ELSE IF min NOT IN [-MaxBBJumps..MaxFBJumps-2] THEN js ← 3
ELSE bindable ← FALSE;
JumpE, JumpN =>
IF max IN [1..MaxFICJumps] THEN js ← 1
ELSE IF max IN (MaxFICJumps..MaxFBJumps-2] AND min > MaxFICJumps THEN js ← 2
ELSE IF max IN [-MaxBBJumps..0] THEN js ← 2
ELSE IF min NOT IN [-MaxBBJumps..MaxFBJumps-2] THEN js ← 4
ELSE bindable ← FALSE;
JumpCA =>
IF max IN [-MaxBBJumps..MaxFBJumps-2] THEN js ← 2
ELSE IF min NOT IN [-MaxBBJumps..MaxFBJumps-2] THEN js ← 3
ELSE bindable ← FALSE;
ENDCASE =>
IF max IN [-MaxBBJumps..MaxFBJumps-2] THEN js ← 2
ELSE IF min NOT IN [-MaxBBJumps..MaxFBJumps-2] THEN js ← 5
ELSE bindable ← FALSE;
IF bindable THEN {cb[c].fixedup ← TRUE; cb[c].jsize ← js};
RETURN
END;
CodeJump:
PUBLIC
PROC [nbytes:
INTEGER, c: JumpCCIndex] =
BEGIN -- code all jump instruction(s)
l: [0..7] = cb[c].jsize;
forward: BOOL = cb[c].forward;
dist: INTEGER ← IF ~forward THEN -nbytes ELSE nbytes+l;
IF l > 3 THEN dist ← dist + 3 - l;
Computing dist copes with the fact that the parameter to a jump
instruction is added to the byte pc of the first byte of the instruction
nbytes is the number of bytes between the jump and its label
CPtr.codeptr ← c;
P5F.CodeJumpDist[dist, l, c];
END;
dMinMax:
ARRAY {unconditional, equal, relational}
OF
PACKED
ARRAY
BOOL
OF
RECORD [min,max: [0..15]] ← [
[[2,3], [1,3]], -- unconditional, (backward, forward)
[[2,4], [1,4]], -- equal, (backward, forward)
[[2,5], [2,5]]]; -- relational, (backward, forward)
FillInPCEstimates:
PUBLIC
PROC =
BEGIN
min, max: RelativePC ← 0;
FOR k: CCIndex ← P5F.StartIndex, cb[k].flink
UNTIL k = CCNull
DO
WITH cc:cb[k]
SELECT
FROM
code =>
BEGIN
t: CARDINAL = cc.isize;
min ← min + t;
max ← max + t;
END;
jump =>
IF cc.jtype # JumpC
THEN
BEGIN
IF ~cc.fixedup
THEN
BEGIN
dMin, dMax: [0..15];
[dMin,dMax] ← dMinMax[(
SELECT cc.jtype
FROM
Jump, JumpA, JumpCA => unconditional,
JumpE, JumpN => equal,
ENDCASE => relational)][cc.forward];
IF ~cc.forward THEN {cc.minPC ← min; cc.maxPC ← max};
min ← min+dMin; max ← max+dMax;
IF cc.forward THEN {cc.minPC ← min; cc.maxPC ← max};
END
ELSE
IF ~cc.completed
THEN
BEGIN
t: CARDINAL = cc.jsize;
IF ~cc.forward THEN {cc.minPC ← min; cc.maxPC ← max};
min ← min + t;
max ← max + t;
IF cc.forward THEN {cc.minPC ← min; cc.maxPC ← max};
END;
END;
label => {cc.minPC ← min; cc.maxPC ← max};
other =>
WITH cc
SELECT
FROM
table =>
BEGIN
min ← min + tablecodebytes;
max ← max + tablecodebytes;
END;
ENDCASE;
ENDCASE;
ENDLOOP;
END;
END.