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MovZX->MovSX optimisation

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J. Gareth "Curious Kit" Moreton 2021-12-06 06:19:25 +00:00 committed by FPK
parent 4825d2d16c
commit 01e5f4855a
1 changed files with 44 additions and 0 deletions
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44
compiler/x86/aoptx86.pas
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@ -7937,6 +7937,9 @@ unit aoptx86;
function TX86AsmOptimizer.OptPass2Movx(var p : tai) : boolean;
label
{ This label permits the case block for MOVSX/D to pass into the MOVZX block }
movzx_cascade;
var
ThisReg: TRegister;
MinSize, MaxSize, TrySmaller, TargetSize: TOpSize;
@ -8436,6 +8439,46 @@ unit aoptx86;
Break;
end;
*)
A_MOVSX{$ifdef x86_64}, A_MOVSXD{$endif x86_64}:
begin
{ If there are no instructions in between, then we might be able to make a saving }
if (InstrMax <> -1) or (taicpu(hp1).oper[0]^.typ <> top_reg) or (taicpu(hp1).oper[0]^.reg <> ThisReg) then
Break;
{ We have something like:
movzbw %dl,%dx
...
movswl %dx,%edx
Change the latter to a zero-extension then enter the
A_MOVZX case branch.
}
{$ifdef x86_64}
if taicpu(hp1).opcode = A_MOVSXD then
begin
{ this becomes a zero extension from 32-bit to 64-bit, but
the upper 32 bits are already zero, so just delete the
instruction }
DebugMsg(SPeepholeOptimization + 'MovzMovsxd2MovzNop', hp1);
RemoveInstruction(hp1);
Result := True;
Exit;
end
else
{$endif x86_64}
begin
DebugMsg(SPeepholeOptimization + 'MovzMovs2MovzMovz', hp1);
taicpu(hp1).opcode := A_MOVZX;
Result := True;
{ Enter the A_MOVZX block below }
goto movzx_cascade;
end;
end;
A_MOVZX:
begin
if not MatchOpType(taicpu(hp1), top_reg, top_reg) then
@ -8460,6 +8503,7 @@ unit aoptx86;
Break;
end;
movzx_cascade:
{ The objective here is to try to find a combination that
removes one of the MOV/Z instructions. }
case taicpu(hp1).opsize of