Improve code generation for comparisons.
This converts comparisons like x > N (with constant N) to instead be evaluated as x >= N+1, since >= comparisons generate better code. This is possible as long as N is not the maximum value in the type, but in that case the comparison is always false. There are also a few other tweaks to the generated code in some cases.
This commit is contained in:
Stephen Heumann
parent
7b0dda5a5e
commit
9b31e7f72a
1
CGI.pas
1
CGI.pas
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@ -148,6 +148,7 @@ const
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m_ply = 122;
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m_plp = 40;
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m_rep = 194;
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m_rol_a = $2A;
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m_ror_a = $6A;
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m_rtl = 107;
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m_rts = 96;
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143
Gen.pas
143
Gen.pas
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@ -1017,6 +1017,7 @@ var
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lab1,lab2,lab3,lab4: integer; {label numbers}
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num: integer; {constant to compare to}
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simple: boolean; {is this a simple case?}
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alwaysFalse: boolean; {is the comparison always false?}
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procedure Switch;
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@ -1067,36 +1068,38 @@ if (op^.optype in [cgByte,cgUByte,cgWord,cgUWord]) and
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(op^.right^.opcode = pc_ldc) then begin
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GenTree(op^.left);
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num := op^.right^.q;
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{Convert x > N comparisons to x >= N+1, unless N is max value }
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{(in which case x > N is always false). }
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alwaysFalse := false;
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if op^.opcode = pc_grt then begin
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if ((op^.optype in [cgByte,cgWord]) and (num = 32767))
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or ((op^.optype in [cgUByte,cgUWord]) and (num = -1)) then
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alwaysFalse := true
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else begin
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op^.opcode := pc_geq;
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num := num+1;
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end; {else}
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end; {if}
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lab1 := GenLabel;
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if rOpcode = pc_fjp then begin
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if op^.optype in [cgByte,cgWord] then begin
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if alwaysFalse then
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GenNative(m_brl, longrelative, lb, nil, 0)
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else if op^.optype in [cgByte,cgWord] then begin
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if NeedsCondition(op^.left^.opcode) then
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GenImpliedForFlags(m_tax);
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if (num >= 0) and (num < 4) then begin
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if op^.opcode = pc_geq then begin
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if num <> 0 then begin
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lab2 := GenLabel;
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GenNative(m_bmi, relative, lab2, nil, 0);
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for i := 1 to num do
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GenImplied(m_dea);
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end; {if}
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GenNative(m_bpl, relative, lab1, nil, 0);
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if num <> 0 then
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GenLab(lab2);
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GenNative(m_brl, longrelative, lb, nil, 0);
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GenLab(lab1);
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end {if}
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else {if opcode = pc_grt then} begin
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if (num >= 0) and (num < 3) then begin
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if num <> 0 then begin
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lab2 := GenLabel;
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GenNative(m_bmi, relative, lab2, nil, 0);
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for i := 0 to num do
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for i := 1 to num do
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GenImplied(m_dea);
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GenNative(m_bpl, relative, lab1, nil, 0);
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end; {if}
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GenNative(m_bpl, relative, lab1, nil, 0);
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if num <> 0 then
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GenLab(lab2);
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GenNative(m_brl, longrelative, lb, nil, 0);
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GenLab(lab1);
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end; {else if}
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end {if (num >= 0) and (num < 4)}
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GenNative(m_brl, longrelative, lb, nil, 0);
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GenLab(lab1);
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end {if (num >= 0) and (num < 3)}
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else begin
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lab2 := GenLabel;
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if num > 0 then
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@ -1104,14 +1107,7 @@ if (op^.optype in [cgByte,cgUByte,cgWord,cgUWord]) and
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else
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GenNative(m_bpl, relative, lab1, nil, 0);
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GenNative(m_cmp_imm, immediate, num, nil, 0);
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if op^.opcode = pc_grt then begin
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lab3 := GenLabel;
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GenNative(m_beq, relative, lab3, nil, 0);
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GenNative(m_bcs, relative, lab2, nil, 0);
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GenLab(lab3);
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end
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else
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GenNative(m_bcs, relative, lab2, nil, 0);
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GenNative(m_bcs, relative, lab2, nil, 0);
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if num > 0 then begin
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GenLab(lab1);
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GenNative(m_brl, longrelative, lb, nil, 0);
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@ -1124,49 +1120,30 @@ if (op^.optype in [cgByte,cgUByte,cgWord,cgUWord]) and
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end; {else if}
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end {if}
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else {if optype in [cgUByte,cgUWord] then} begin
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GenNative(m_cmp_imm, immediate, num, nil, 0);
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if op^.opcode = pc_grt then begin
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lab2 := GenLabel;
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GenNative(m_beq, relative, lab2, nil, 0);
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if num <> 0 then begin
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GenNative(m_cmp_imm, immediate, num, nil, 0);
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GenNative(m_bcs, relative, lab1, nil, 0);
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GenNative(m_brl, longrelative, lb, nil, 0);
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GenLab(lab1);
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end; {if}
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GenNative(m_bcs, relative, lab1, nil, 0);
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if op^.opcode = pc_grt then
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GenLab(lab2);
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GenNative(m_brl, longrelative, lb, nil, 0);
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GenLab(lab1);
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end; {else}
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end {if rOpcode = pc_fjp}
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else if rOpcode = pc_tjp then begin
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if op^.optype in [cgByte,cgWord] then begin
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if alwaysFalse then
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{nothing to generate}
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else if op^.optype in [cgByte,cgWord] then begin
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if NeedsCondition(op^.left^.opcode) then
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GenImpliedForFlags(m_tax);
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if (num >= 0) and (num < 4) then begin
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lab2 := GenLabel;
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if op^.opcode = pc_geq then begin
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if (num >= 0) and (num < 3) then begin
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GenNative(m_bmi, relative, lab1, nil, 0);
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if num > 0 then begin
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for i := 1 to num do
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GenImplied(m_dea);
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GenNative(m_bmi, relative, lab1, nil, 0);
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if num > 0 then begin
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for i := 1 to num do
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GenImplied(m_dea);
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GenNative(m_bmi, relative, lab2, nil, 0);
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end; {if}
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GenNative(m_brl, longrelative, lb, nil, 0);
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end {if}
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else {if op^.opcode = pc_grt then} begin
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if num > 0 then begin
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GenNative(m_bmi, relative, lab1, nil, 0);
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for i := 0 to num do
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GenImplied(m_dea);
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GenNative(m_bmi, relative, lab2, nil, 0);
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end {if}
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else begin
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GenNative(m_beq, relative, lab1, nil, 0);
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GenNative(m_bmi, relative, lab2, nil, 0);
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end; {else}
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GenNative(m_brl, longrelative, lb, nil, 0);
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end; {else}
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GenLab(lab2);
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end; {if}
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GenNative(m_brl, longrelative, lb, nil, 0);
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GenLab(lab1);
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end {if (num >= 0) and (num < 4)}
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end {if (num >= 0) and (num < 3)}
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else begin
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lab2 := GenLabel;
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if num > 0 then
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@ -1174,10 +1151,6 @@ if (op^.optype in [cgByte,cgUByte,cgWord,cgUWord]) and
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else
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GenNative(m_bpl, relative, lab1, nil, 0);
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GenNative(m_cmp_imm, immediate, num, nil, 0);
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if op^.opcode = pc_grt then begin
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lab3 := GenLabel;
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GenNative(m_beq, relative, lab3, nil, 0);
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end; {if}
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GenNative(m_bcc, relative, lab2, nil, 0);
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if num > 0 then begin
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GenNative(m_brl, longrelative, lb, nil, 0);
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@ -1189,51 +1162,37 @@ if (op^.optype in [cgByte,cgUByte,cgWord,cgUWord]) and
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GenNative(m_brl, longrelative, lb, nil, 0);
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GenLab(lab2);
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end; {else}
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if op^.opcode = pc_grt then
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GenLab(lab3);
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end; {else}
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end {if}
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else {if optype in [cgUByte,cgUWord] then} begin
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GenNative(m_cmp_imm, immediate, num, nil, 0);
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GenNative(m_bcc, relative, lab1, nil, 0);
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if op^.opcode = pc_grt then begin
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lab2 := GenLabel;
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GenNative(m_beq, relative, lab1, nil, 0);
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if num <> 0 then begin
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GenNative(m_cmp_imm, immediate, num, nil, 0);
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GenNative(m_bcc, relative, lab1, nil, 0);
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end; {if}
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GenNative(m_brl, longrelative, lb, nil, 0);
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if op^.opcode = pc_grt then
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GenLab(lab2);
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GenLab(lab1);
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if num <> 0 then
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GenLab(lab1);
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end; {else}
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end {if rOpcode = pc_tjp}
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else if alwaysFalse then
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GenNative(m_lda_imm, immediate, 0, nil, 0)
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else if op^.optype in [cgByte,cgWord] then begin
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lab2 := GenLabel;
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GenNative(m_ldx_imm, immediate, 1, nil, 0);
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GenImplied(m_sec);
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GenNative(m_sbc_imm, immediate, num, nil, 0);
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if op^.opcode = pc_grt then begin
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lab3 := GenLabel;
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GenNative(m_beq, relative, lab3, nil, 0);
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end; {if}
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GenNative(m_bvs, relative, lab1, nil, 0);
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GenNative(m_eor_imm, immediate, $8000, nil, 0);
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GenLab(lab1);
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GenNative(m_bmi, relative, lab2, nil, 0);
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if op^.opcode = pc_grt then
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GenLab(lab3);
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GenImplied(m_dex);
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GenLab(lab2);
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GenImplied(m_txa);
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end {else if}
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else begin
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GenNative(m_ldx_imm, immediate, 0, nil, 0);
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GenNative(m_cmp_imm, immediate, num, nil, 0);
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GenNative(m_bcc, relative, lab1, nil, 0);
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if op^.opcode = pc_grt then
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GenNative(m_beq, relative, lab1, nil, 0);
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GenImplied(m_inx);
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GenLab(lab1);
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GenImplied(m_txa);
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GenNative(m_lda_imm, immediate, 0, nil, 0);
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GenImplied(m_rol_a);
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end; {else if}
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end {if (op^.optype in [cgByte,cgUByte,cgWord,cgUWord]) and
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(op^.right^.opcode = pc_ldc)}
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@ -793,7 +793,7 @@ label 1,2,3;
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m_ina,m_lda_abs,m_lda_absx,m_lda_dir,m_lda_dirx,m_lda_imm,m_lda_indl,
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m_lda_indly,m_lda_long,m_lda_longx,m_lda_s,m_lsr_a,m_ora_abs,m_ora_dir,
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m_ora_dirX,m_ora_imm,m_ora_long,m_ora_longX,m_ora_s,m_ora_indl,
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m_ora_indly,m_pla,m_ror_a,m_sbc_abs,m_sbc_dir,m_sbc_imm,m_sbc_s,
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m_ora_indly,m_pla,m_rol_a,m_ror_a,m_sbc_abs,m_sbc_dir,m_sbc_imm,m_sbc_s,
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m_sbc_indl,m_sbc_indly,m_tax,m_tay,m_tcd,m_tdc,m_txa,m_tya];
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end; {NZMatchA}
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@ -805,7 +805,7 @@ case p_opcode of
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m_ora_dir,m_ora_dirX,m_ora_imm,m_ora_long,m_ora_longX,m_ora_s,m_pla,
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m_sbc_abs,m_sbc_dir,m_sbc_imm,m_sbc_s,m_tdc,m_tsc,m_adc_indl,m_adc_indly,
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m_and_indl,m_and_indly,m_ora_indl,m_ora_indly,m_sbc_indl,m_sbc_indly,
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m_eor_indl,m_eor_indly,m_ror_a:
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m_eor_indl,m_eor_indly,m_rol_a,m_ror_a:
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aRegister.condition := regUnknown;
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m_ldy_absX,m_ldy_dirX,m_ply:
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