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* x86: New "Jcc; CLC/STC; .Lbl" optimisation

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This commit is contained in:
J. Gareth "Curious Kit" Moreton 2024-01-27 23:58:33 +00:00 committed by FPK
parent c29dd86bb2
commit d06dd2b0ea
1 changed files with 52 additions and 1 deletions
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53
compiler/x86/aoptx86.pas
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@ -8626,8 +8626,9 @@ unit aoptx86;
function TX86AsmOptimizer.OptPass1Jcc(var p : tai) : boolean;
var
hp1, hp2, hp3, hp4, hp5, hp6: tai;
hp1, hp2, hp3, hp4, hp5: tai;
ThisReg: TRegister;
TempBool: Boolean;
begin
Result := False;
if not GetNextInstruction(p,hp1) then
@ -8785,6 +8786,56 @@ unit aoptx86;
Result:=true;
exit;
end
else if MatchInstruction(hp1, A_CLC, A_STC, []) then
begin
{
j(c) .L1
stc/clc
.L1:
jc/jnc .L2
(Flags deallocated)
Change to:
j)c) .L1
jmp .L2
.L1:
jc/jnc .L2
Then call DoJumpOptimizations to convert to:
j(nc) .L2
.L1: (may become a dead label)
jc/jnc .L2
}
if GetNextInstruction(hp1, hp2) and
(hp2.typ = ait_label) and
(tai_label(hp2).labsym = TAsmLabel(taicpu(p).oper[0]^.ref^.symbol)) and
GetNextInstruction(hp2, hp3) and
MatchInstruction(hp3, A_Jcc, []) and
(
(
(taicpu(hp3).condition = C_C) and
(taicpu(hp1).opcode = A_STC)
) or (
(taicpu(hp3).condition = C_NC) and
(taicpu(hp1).opcode = A_CLC)
)
) and
{ Make sure the flags aren't used again }
Assigned(FindRegDealloc(NR_DEFAULTFLAGS, tai(hp3.Next))) then
begin
taicpu(hp1).allocate_oper(1);
taicpu(hp1).ops := 1;
taicpu(hp1).loadsymbol(0, TAsmLabel(taicpu(hp3).oper[0]^.ref^.symbol), 0);
taicpu(hp1).opcode := A_JMP;
taicpu(hp1).is_jmp := True;
TempBool := True; { Prevent compiler warnings }
if DoJumpOptimizations(p, TempBool) then
Result := True
else
Include(OptsToCheck, aoc_ForceNewIteration);
end;
end
else if (hp1.typ = ait_label) then
Result := DoSETccLblRETOpt(p, tai_label(hp1));
end;