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Generate more efficient code for 16-bit signed comparisons.

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The new code is smaller and (in the common case where the subtraction does not overflow) faster. It takes advantage of the fact that in overflow cases the carry flag always gets set to the opposite of the sign bit of the result.
This commit is contained in:
Stephen Heumann 2023-03-18 20:05:56 -05:00
parent 137188ff4f
commit a5eafe56af
3 changed files with 18 additions and 17 deletions
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1
CGI.pas
View File

@ -71,6 +71,7 @@ const
m_bpl = $10; m_bpl = $10;
m_bra = $80; m_bra = $80;
m_brl = $82; m_brl = $82;
m_bvc = $50;
m_bvs = $70; m_bvs = $70;
m_clc = $18; m_clc = $18;
m_cmp_abs = $CD; m_cmp_abs = $CD;

24
Gen.pas
View File

@ -1212,10 +1212,10 @@ if (op^.optype in [cgByte,cgUByte,cgWord,cgUWord]) and
GenNative(m_ldx_imm, immediate, 1, nil, 0); GenNative(m_ldx_imm, immediate, 1, nil, 0);
GenImplied(m_sec); GenImplied(m_sec);
GenNative(m_sbc_imm, immediate, num, nil, 0); GenNative(m_sbc_imm, immediate, num, nil, 0);
GenNative(m_bvs, relative, lab1, nil, 0); GenNative(m_bvc, relative, lab1, nil, 0);
GenNative(m_eor_imm, immediate, $8000, nil, 0); GenImplied(m_ror_a);
GenLab(lab1); GenLab(lab1);
GenNative(m_bmi, relative, lab2, nil, 0); GenNative(m_bpl, relative, lab2, nil, 0);
GenImplied(m_dex); GenImplied(m_dex);
GenLab(lab2); GenLab(lab2);
GenImplied(m_txa); GenImplied(m_txa);
@ -1279,10 +1279,10 @@ else
end; {if} end; {if}
if op^.optype in [cgByte,cgWord] then begin if op^.optype in [cgByte,cgWord] then begin
lab1 := GenLabel; lab1 := GenLabel;
GenNative(m_bvs, relative, lab1, nil, 0); GenNative(m_bvc, relative, lab1, nil, 0);
GenNative(m_eor_imm, immediate, $8000, nil, 0); GenImplied(m_ror_a);
GenLab(lab1); GenLab(lab1);
GenNative(m_bmi, relative, lab2, nil, 0); GenNative(m_bpl, relative, lab2, nil, 0);
end {if} end {if}
else else
GenNative(m_bcs, relative, lab2, nil, 0); GenNative(m_bcs, relative, lab2, nil, 0);
@ -1299,10 +1299,10 @@ else
end; {if} end; {if}
if op^.optype in [cgByte,cgWord] then begin if op^.optype in [cgByte,cgWord] then begin
lab1 := GenLabel; lab1 := GenLabel;
GenNative(m_bvs, relative, lab1, nil, 0); GenNative(m_bvc, relative, lab1, nil, 0);
GenNative(m_eor_imm, immediate, $8000, nil, 0); GenImplied(m_ror_a);
GenLab(lab1); GenLab(lab1);
GenNative(m_bpl, relative, lab2, nil, 0); GenNative(m_bmi, relative, lab2, nil, 0);
end {if} end {if}
else else
GenNative(m_bcc, relative, lab2, nil, 0); GenNative(m_bcc, relative, lab2, nil, 0);
@ -1319,10 +1319,10 @@ else
end; {if} end; {if}
if op^.optype in [cgByte,cgWord] then begin if op^.optype in [cgByte,cgWord] then begin
lab1 := GenLabel; lab1 := GenLabel;
GenNative(m_bvs, relative, lab1, nil, 0); GenNative(m_bvc, relative, lab1, nil, 0);
GenNative(m_eor_imm, immediate, $8000, nil, 0); GenImplied(m_ror_a);
GenLab(lab1); GenLab(lab1);
GenNative(m_bmi, relative, lab2, nil, 0); GenNative(m_bpl, relative, lab2, nil, 0);
end {if} end {if}
else else
GenNative(m_bcs, relative, lab2, nil, 0); GenNative(m_bcs, relative, lab2, nil, 0);

10
Native.pas
View File

@ -849,7 +849,7 @@ case p_opcode of
m_plx: m_plx:
xRegister.condition := regUnknown; xRegister.condition := regUnknown;
m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvs, m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvc,m_bvs,
m_pha,m_phb,m_phd,m_php,m_phx,m_phy,m_pei_dir,m_tcs: m_pha,m_phb,m_phd,m_php,m_phx,m_phy,m_pei_dir,m_tcs:
goto 3; goto 3;
@ -1558,7 +1558,7 @@ var
for i := ns to nnextSpot-1 do begin for i := ns to nnextSpot-1 do begin
opcode := npeep[i].opcode; opcode := npeep[i].opcode;
if opcode in if opcode in
[m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bra,m_brl,m_bvs,m_jml, [m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bra,m_brl,m_bvc,m_bvs,m_jml,
m_jmp_indX,m_jsl,m_lda_abs,m_lda_absx,m_lda_dir,m_lda_dirx, m_jmp_indX,m_jsl,m_lda_abs,m_lda_absx,m_lda_dir,m_lda_dirx,
m_lda_imm,m_lda_indl,m_lda_indly,m_lda_long,m_lda_longx,m_lda_s, m_lda_imm,m_lda_indl,m_lda_indly,m_lda_long,m_lda_longx,m_lda_s,
m_pla,m_rtl,m_rts,m_tdc,m_txa,m_tya,m_tsc,d_end,d_bmov, m_pla,m_rtl,m_rts,m_tdc,m_txa,m_tya,m_tsc,d_end,d_bmov,
@ -1881,14 +1881,14 @@ var
if operand = npeep[ns+1].operand then if operand = npeep[ns+1].operand then
if name = npeep[ns+1].name then if name = npeep[ns+1].name then
if not (npeep[ns+2].opcode in if not (npeep[ns+2].opcode in
[m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvs]) then [m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvc,m_bvs]) then
Remove(ns+1); Remove(ns+1);
m_sta_dir: m_sta_dir:
if npeep[ns+1].opcode = m_lda_dir then if npeep[ns+1].opcode = m_lda_dir then
if operand = npeep[ns+1].operand then if operand = npeep[ns+1].operand then
if not (npeep[ns+2].opcode in if not (npeep[ns+2].opcode in
[m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvs]) then [m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvc,m_bvs]) then
Remove(ns+1); Remove(ns+1);
m_plb: m_plb:
@ -1913,7 +1913,7 @@ var
end {if} end {if}
else if npeep[ns+1].opcode = m_txa then begin else if npeep[ns+1].opcode = m_txa then begin
if not (npeep[ns+2].opcode in if not (npeep[ns+2].opcode in
[m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvs]) then begin [m_bcc,m_bcs,m_beq,m_bmi,m_bne,m_bpl,m_bvc,m_bvs]) then begin
Remove(ns); Remove(ns);
Remove(ns); Remove(ns);
end; {if} end; {if}