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* convert n-n mod const into n div const*const, resolves #39615

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This commit is contained in:
florian 2022-11-22 22:41:58 +01:00
parent 7da8c774be
commit 0ba4cee279
3 changed files with 70 additions and 0 deletions
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10
compiler/nadd.pas
View File

@ -958,6 +958,16 @@ implementation
exit;
end;
{ convert n - n mod const into n div const*const }
if (nodetype=subn) and (right.nodetype=modn) and is_constintnode(taddnode(right).right) and
(left.isequal(taddnode(right).left)) and not(might_have_sideeffects(left)) then
begin
result:=caddnode.create_internal(muln,cmoddivnode.create(divn,left,taddnode(right).right.getcopy),taddnode(right).right);
left:=nil;
taddnode(right).right:=nil;
exit;
end;
{ both real constants ? }
if (lt=realconstn) and (rt=realconstn) then
begin

30
tests/webtbs/tw39615a.pp Normal file
View File

@ -0,0 +1,30 @@
{ $define unsigned}
const
Divisor = 17;
TestRange = 3 * Divisor;
var
i, x, r1, r2: {$ifdef unsigned} uint32 {$else} int32 {$endif};
ok: boolean;
begin
ok := true;
for i := {$ifdef unsigned} 0 {$else} -2 * TestRange {$endif} to 2 * TestRange do
begin
{$ifndef unsigned}
if i < -TestRange then
x := Low(x) + (i - (-2 * TestRange)) // test [Low(x); Low(x) + TestRange)
else
{$endif}
if i <= TestRange then x := i // test [-TestRange; TestRange] or [0; TestRange]
else x := High(x) - (i - TestRange - 1); // test (High(x) - TestRange; High(x)]
r1 := x - x mod Divisor;
r2 := x div Divisor * Divisor;
if r1 <> r2 then
begin
writeln('FAIL: x=', x, ', x - x mod ', Divisor, ' = ', r1, ', x div ', Divisor, ' * ', Divisor, ' = ', r2);
ok := false;
end;
end;
if ok then writeln('ok');
end.

30
tests/webtbs/tw39615b.pp Normal file
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@ -0,0 +1,30 @@
{$define unsigned}
const
Divisor = 17;
TestRange = 3 * Divisor;
var
i, x, r1, r2: {$ifdef unsigned} uint32 {$else} int32 {$endif};
ok: boolean;
begin
ok := true;
for i := {$ifdef unsigned} 0 {$else} -2 * TestRange {$endif} to 2 * TestRange do
begin
{$ifndef unsigned}
if i < -TestRange then
x := Low(x) + (i - (-2 * TestRange)) // test [Low(x); Low(x) + TestRange)
else
{$endif}
if i <= TestRange then x := i // test [-TestRange; TestRange] or [0; TestRange]
else x := High(x) - (i - TestRange - 1); // test (High(x) - TestRange; High(x)]
r1 := x - x mod Divisor;
r2 := x div Divisor * Divisor;
if r1 <> r2 then
begin
writeln('FAIL: x=', x, ', x - x mod ', Divisor, ' = ', r1, ', x div ', Divisor, ' * ', Divisor, ' = ', r2);
ok := false;
end;
end;
if ok then writeln('ok');
end.