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Optimize division/remainder by various constants. 

This generally covers powers of two and certain other values. (Details differ for signed/unsigned div/rem.)
This commit is contained in:
Stephen Heumann 2022-07-09 15:05:47 -05:00
parent 054719aab2
commit 4470626ade
1 changed files with 146 additions and 5 deletions
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151
Gen.pas
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@ -5722,10 +5722,152 @@ procedure GenTree {op: icptr};
var
opcode: pcodes; {temp storage}
lab1: integer; {label number}
lab1,lab2,lab3: integer; {label numbers}
val: integer;
power: integer;
begin {GenDviMod}
if Complex(op^.right) then begin
opcode := op^.opcode;
if (op^.right^.opcode = pc_ldc) and not rangeCheck then begin
val := op^.right^.q;
if opcode = pc_udi then begin
case val of
1,2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384: begin
GenTree(op^.left);
if val >= 256 then begin
GenNative(m_and_imm, immediate, $FF00, nil, 0);
GenImplied(m_xba);
val := val >> 8;
end; {if}
while not odd(val) do begin
GenImplied(m_lsr_a);
val := val >> 1;
end; {while}
opcode := pc_nop;
end;
otherwise:
if (val >= 1000) or (val < 0) then begin {1000..65535}
GenTree(op^.left);
lab1 := GenLabel;
GenNative(m_ldy_imm, immediate, -1, nil, 0);
GenImplied(m_sec);
GenLab(lab1);
GenImplied(m_iny);
GenNative(m_sbc_imm, immediate, val, nil, 0);
GenNative(m_bcs, relative, lab1, nil, 0);
GenImplied(m_tya);
opcode := pc_nop;
end; {if}
end; {case}
end {if}
else if opcode = pc_uim then begin
case val of
1: begin
GenTree(op^.left);
GenNative(m_lda_imm, immediate, 0, nil, 0);
opcode := pc_nop;
end;
2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384: begin
GenTree(op^.left);
power := 0;
while power < val/2 do
power := (power << 1) + 1;
GenNative(m_and_imm, immediate, power, nil, 0);
opcode := pc_nop;
end;
otherwise:
if (val >= 750) or (val < 0) then begin {750..65535}
GenTree(op^.left);
lab1 := GenLabel;
GenImplied(m_sec);
GenLab(lab1);
GenNative(m_sbc_imm, immediate, val, nil, 0);
GenNative(m_bcs, relative, lab1, nil, 0);
GenNative(m_adc_imm, immediate, val, nil, 0);
opcode := pc_nop;
end; {if}
end; {case}
end {else if}
else if opcode = pc_dvi then begin
case val of
-1: begin
GenTree(op^.left);
GenNative(m_eor_imm, immediate, -1, nil, 0);
GenImplied(m_ina);
opcode := pc_nop;
end;
1: begin
GenTree(op^.left);
opcode := pc_nop;
end;
2,4,8,16,32,64,128,256,512,1024,2048,4096,8192,16384: begin
GenTree(op^.left);
power := 0;
while not odd(val) do begin
power := power + 1;
val := val >> 1;
end; {while}
if power <> 1 then
GenNative(m_ldy_imm, immediate, power, nil, 0);
lab1 := GenLabel;
lab2 := GenLabel;
lab3 := GenLabel;
GenLab(lab1);
GenImplied(m_clc);
GenImplied(m_tax);
GenNative(m_bpl, relative, lab2, nil, 0);
GenImplied(m_ina);
GenNative(m_beq, relative, lab3, nil, 0);
GenImplied(m_sec);
GenLab(lab2);
GenImplied(m_ror_a);
if power <> 1 then begin
GenImplied(m_dey);
GenNative(m_bne, relative, lab1, nil, 0);
end; {if}
GenLab(lab3);
opcode := pc_nop;
end;
otherwise: ;
end; {case}
end {else if}
else {if opcode = pc_mod then} begin
case val of
-1,1: begin
GenTree(op^.left);
GenNative(m_lda_imm, immediate, 0, nil, 0);
opcode := pc_nop;
end;
2: begin
GenTree(op^.left);
lab1 := GenLabel;
lab2 := GenLabel;
GenImplied(m_asl_a);
GenNative(m_and_imm, immediate, 2, nil, 0);
GenNative(m_beq, relative, lab2, nil, 0);
GenNative(m_bcc, relative, lab1, nil, 0);
GenImplied(m_dea);
GenImplied(m_dea);
GenLab(lab1);
GenImplied(m_dea);
GenLab(lab2);
opcode := pc_nop;
end;
otherwise: ;
end; {case}
end; {else}
end; {if}
if opcode = pc_nop then
{nothing to do - optimized above}
else if Complex(op^.right) then begin
GenTree(op^.right);
if Complex(op^.left) then begin
GenImplied(m_pha);
@ -5736,12 +5878,11 @@ procedure GenTree {op: icptr};
GenImplied(m_tax);
GenTree(op^.left);
end; {else}
end {if}
end {else if}
else begin
GenTree(op^.left);
LoadX(op^.right);
end; {else}
opcode := op^.opcode;
if opcode = pc_mod then begin
lab1 := GenLabel;
GenImplied(m_pha); {stash away dividend (for sign)}
@ -5755,7 +5896,7 @@ procedure GenTree {op: icptr};
end {if}
else if opcode = pc_dvi then
GenCall(26)
else {if opcode in [pc_udi,pc_uim] then} begin
else if opcode in [pc_udi,pc_uim] then begin
GenCall(40);
if opcode = pc_uim then
GenImplied(m_txa);