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@@ -2194,6 +2194,7 @@ unit aoptx86;
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function TX86AsmOptimizer.OptPass1MOV(var p : tai) : boolean;
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var
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hp1, hp2, hp3: tai;
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+ DoOptimisation, TempBool: Boolean;
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procedure convert_mov_value(signed_movop: tasmop; max_value: tcgint); inline;
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begin
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@@ -2622,7 +2623,120 @@ unit aoptx86;
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}
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TransferUsedRegs(TmpUsedRegs);
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UpdateUsedRegs(TmpUsedRegs, tai(p.Next));
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- if not (RegInUsedRegs(NR_DEFAULTFLAGS, TmpUsedRegs)) then
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+ DoOptimisation := True;
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+
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+ { Even if the flags are used, we might be able to do the optimisation
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+ if the conditions are predictable }
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+ if RegInUsedRegs(NR_DEFAULTFLAGS, TmpUsedRegs) then
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+ begin
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+ { Only perform if ### = %reg (the same register) or equal to 0,
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+ so %reg is guaranteed to still have a value of zero }
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+ if MatchOperand(taicpu(hp1).oper[0]^, 0) or
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+ MatchOperand(taicpu(hp1).oper[0]^, taicpu(hp1).oper[1]^.reg) then
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+ begin
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+ hp2 := hp1;
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+ UpdateUsedRegs(TmpUsedRegs, tai(hp1.Next));
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+ while RegInUsedRegs(NR_DEFAULTFLAGS, TmpUsedRegs) and
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+ GetNextInstruction(hp2, hp3) do
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+ begin
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+ { Don't continue modifying if the flags state is getting changed }
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+ if RegModifiedByInstruction(NR_DEFAULTFLAGS, hp3) then
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+ Break;
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+
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+ UpdateUsedRegs(TmpUsedRegs, tai(hp3.Next));
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+ if MatchInstruction(hp3, A_Jcc, A_SETcc, A_CMOVcc, []) then
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+ begin
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+
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+ if condition_in(C_E, taicpu(hp3).condition) or (taicpu(hp3).condition in [C_NC, C_NS, C_NO]) then
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+ begin
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+ { Condition is always true }
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+ case taicpu(hp3).opcode of
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+ A_Jcc:
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+ begin
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+ DebugMsg(SPeepholeOptimization + 'Condition is always true (jump made unconditional)', hp3);
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+ { Check for jump shortcuts before we destroy the condition }
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+ DoJumpOptimizations(hp3, TempBool);
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+ MakeUnconditional(taicpu(hp3));
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+ Result := True;
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+ end;
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+ A_CMOVcc:
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+ begin
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+ DebugMsg(SPeepholeOptimization + 'Condition is always true (CMOVcc -> MOV)', hp3);
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+ taicpu(hp3).opcode := A_MOV;
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+ taicpu(hp3).condition := C_None;
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+ Result := True;
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+ end;
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+ A_SETcc:
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+ begin
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+ DebugMsg(SPeepholeOptimization + 'Condition is always true (changed to MOV 1)', hp3);
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+ { Convert "set(c) %reg" instruction to "movb 1,%reg" }
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+ taicpu(hp3).opcode := A_MOV;
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+ taicpu(hp3).ops := 2;
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+ taicpu(hp3).condition := C_None;
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+ taicpu(hp3).opsize := S_B;
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+ taicpu(hp3).loadreg(1,taicpu(hp3).oper[0]^.reg);
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+ taicpu(hp3).loadconst(0, 1);
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+ Result := True;
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+ end;
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+ else
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+ InternalError(2021090701);
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+ end;
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+ end
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+ else if (taicpu(hp3).condition in [C_A, C_B, C_C, C_G, C_L, C_NE, C_NZ, C_O, C_S]) then
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+ begin
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+ { Condition is always false }
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+ case taicpu(hp3).opcode of
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+ A_Jcc:
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+ begin
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+ DebugMsg(SPeepholeOptimization + 'Condition is always false (jump removed)', hp3);
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+ TAsmLabel(taicpu(hp3).oper[0]^.ref^.symbol).decrefs;
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+ RemoveInstruction(hp3);
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+ Result := True;
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+ { Since hp3 was deleted, hp2 must not be updated }
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+ Continue;
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+ end;
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+ A_CMOVcc:
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+ begin
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+ DebugMsg(SPeepholeOptimization + 'Condition is always false (conditional load removed)', hp3);
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+ RemoveInstruction(hp3);
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+ Result := True;
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+ { Since hp3 was deleted, hp2 must not be updated }
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+ Continue;
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+ end;
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+ A_SETcc:
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+ begin
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+ DebugMsg(SPeepholeOptimization + 'Condition is always false (changed to MOV 0)', hp3);
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+ { Convert "set(c) %reg" instruction to "movb 0,%reg" }
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+ taicpu(hp3).opcode := A_MOV;
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+ taicpu(hp3).ops := 2;
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+ taicpu(hp3).condition := C_None;
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+ taicpu(hp3).opsize := S_B;
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+ taicpu(hp3).loadreg(1,taicpu(hp3).oper[0]^.reg);
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+ taicpu(hp3).loadconst(0, 0);
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+ Result := True;
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+ end;
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+ else
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+ InternalError(2021090702);
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+ end;
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+ end
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+ else
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+ { Uncertain what to do - don't optimise (although optimise other conditional statements if present) }
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+ DoOptimisation := False;
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+ end;
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+
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+ hp2 := hp3;
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+ end;
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+
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+ { Flags are still in use - don't optimise }
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+ if DoOptimisation and RegInUsedRegs(NR_DEFAULTFLAGS, TmpUsedRegs) then
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+ DoOptimisation := False;
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+
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+ end
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+ else
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+ DoOptimisation := False;
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+ end;
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+
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+ if DoOptimisation then
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begin
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{$ifdef x86_64}
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{ OR only supports 32-bit sign-extended constants for 64-bit
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Yuriy Sydorov