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Generate more efficient code for certain conditionals.

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This will change a "jump if true" to "jump if false" (or vice versa) and logically negate the condition in certain cases where that generates better code.

An assembly peephole optimization for certain "branch to branch" instructions is also added. (Certain conditionals could generate these.)
This commit is contained in:
Stephen Heumann 2023-03-14 21:32:20 -05:00
parent 7c8ec41148
commit 49deff3c86
2 changed files with 30 additions and 12 deletions
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37
Gen.pas
View File

@ -1051,6 +1051,28 @@ var
op^.right := nd;
end; {Switch}
procedure ReverseConditional;
{ Change tjp to an equivalent fjp, or vice versa. }
{ }
{ Note: assumes opcode is pc_geq or pc_grt. }
begin {ReverseConditional}
if rOpcode in [pc_tjp,pc_fjp] then begin
if op^.opcode = pc_geq then
op^.opcode := pc_grt
else
op^.opcode := pc_geq;
if rOpcode = pc_tjp then
rOpcode := pc_fjp
else
rOpcode := pc_tjp;
Switch;
end; {if}
end; {ReverseConditional}
begin {GenCmp}
{To reduct the number of possibilities that must be handled, pc_les }
{and pc_leq compares are reduced to their equivalent pc_grt and }
@ -1068,17 +1090,7 @@ else if op^.opcode = pc_leq then begin
{for a tjp or fjp with a constant left operand. }
if op^.optype in [cgByte,cgUByte,cgWord,cgUWord] then
if op^.left^.opcode = pc_ldc then
if rOpcode in [pc_tjp,pc_fjp] then begin
if op^.opcode = pc_geq then
op^.opcode := pc_grt
else
op^.opcode := pc_geq;
if rOpcode = pc_tjp then
rOpcode := pc_fjp
else
rOpcode := pc_tjp;
Switch;
end; {if}
ReverseConditional;
{Short cuts are available for single-word operands where the }
{right operand is a constant. }
@ -1222,6 +1234,9 @@ else
case op^.optype of
cgByte,cgUByte,cgWord,cgUWord: begin
if ((op^.opcode = pc_grt) and (Complex(op^.left) <= Complex(op^.right)))
or (Complex(op^.right) and not Complex(op^.left)) then
ReverseConditional;
if Complex(op^.right) then begin
GenTree(op^.right);
if Complex(op^.left) then begin

5
Native.pas
View File

@ -1670,7 +1670,10 @@ var
opcode := m_bcs
else
opcode := m_bmi;
end; {else if m_bra}
end {else if m_bra}
else if npeep[ns+3].opcode in [m_bra,m_brl] then
if Short(ns,npeep[ns+3].operand) then
operand := npeep[ns+3].operand;
m_brl:
if Short(ns,operand) then begin