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Refactoring and bug fix in OptPass2Movx that could cause incorrect

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values in overflow conditions
This commit is contained in:
J. Gareth "Curious Kit" Moreton 2022-01-19 15:59:05 +00:00 committed by FPK
parent 546455faca
commit 5738a6ccf1
1 changed files with 85 additions and 32 deletions
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117
compiler/x86/aoptx86.pas
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@ -8431,7 +8431,7 @@ unit aoptx86;
MinSize, MaxSize, TryShiftDown, TargetSize: TOpSize;
TargetSubReg: TSubRegister;
hp1, hp2: tai;
RegInUse, RegChanged, p_removed: Boolean;
RegInUse, RegChanged, p_removed, hp1_removed: Boolean;
{ Store list of found instructions so we don't have to call
GetNextInstructionUsingReg multiple times }
@ -8480,7 +8480,7 @@ unit aoptx86;
end;
end;
function AdjustInitialLoad: Boolean;
function AdjustInitialLoadAndSize: Boolean;
begin
Result := False;
@ -8535,45 +8535,95 @@ unit aoptx86;
else
;
end;
end
else if not hp1_removed and not RegInUse then
begin
{ If we have something like:
movzbl (oper),%regd
add x, %regd
movzbl %regb, %regd
We can reduce the register size to the input of the final
movzbl instruction. Overflows won't have any effect.
}
if (taicpu(p).opsize in [S_BW, S_BL]) and
(taicpu(hp1).opsize in [S_BW, S_BL{$ifdef x86_64}, S_BQ{$endif x86_64}]) then
begin
TargetSize := S_B;
setsubreg(ThisReg, R_SUBL);
Result := True;
end
else if (taicpu(p).opsize = S_WL) and
(taicpu(hp1).opsize in [S_WL{$ifdef x86_64}, S_BQ{$endif x86_64}]) then
begin
TargetSize := S_W;
setsubreg(ThisReg, R_SUBW);
Result := True;
end;
if Result then
begin
{ Convert the input MOVZX to a MOV }
if (taicpu(p).oper[0]^.typ = top_reg) and
SuperRegistersEqual(taicpu(p).oper[0]^.reg, ThisReg) then
begin
{ Or remove it completely! }
DebugMsg(SPeepholeOptimization + 'Movzx2Nop 1a', p);
RemoveCurrentP(p);
p_removed := True;
end
else
begin
DebugMsg(SPeepholeOptimization + 'Movzx2Mov 1a', p);
taicpu(p).opcode := A_MOV;
taicpu(p).oper[1]^.reg := ThisReg;
taicpu(p).opsize := TargetSize;
end;
end;
end;
end;
end;
procedure AdjustFinalLoad;
begin
if ((TargetSize = S_L) and (taicpu(hp1).opsize in [S_L, S_BL, S_WL])) or
((TargetSize = S_W) and (taicpu(hp1).opsize in [S_W, S_BW])) then
if not LowerUnsignedOverflow then
begin
{ Convert the output MOVZX to a MOV }
if SuperRegistersEqual(taicpu(hp1).oper[1]^.reg, ThisReg) then
if ((TargetSize = S_L) and (taicpu(hp1).opsize in [S_L, S_BL, S_WL])) or
((TargetSize = S_W) and (taicpu(hp1).opsize in [S_W, S_BW])) then
begin
{ Or remove it completely! }
DebugMsg(SPeepholeOptimization + 'Movzx2Nop 2', hp1);
{ Be careful; if p = hp1 and p was also removed, p
will become a dangling pointer }
if p = hp1 then
{ Convert the output MOVZX to a MOV }
if SuperRegistersEqual(taicpu(hp1).oper[1]^.reg, ThisReg) then
begin
RemoveCurrentp(p); { p = hp1 and will then become the next instruction }
p_removed := True;
{ Or remove it completely! }
DebugMsg(SPeepholeOptimization + 'Movzx2Nop 2', hp1);
{ Be careful; if p = hp1 and p was also removed, p
will become a dangling pointer }
if p = hp1 then
begin
RemoveCurrentp(p); { p = hp1 and will then become the next instruction }
p_removed := True;
end
else
RemoveInstruction(hp1);
hp1_removed := True;
end
else
RemoveInstruction(hp1);
begin
DebugMsg(SPeepholeOptimization + 'Movzx2Mov 2', hp1);
taicpu(hp1).opcode := A_MOV;
taicpu(hp1).oper[0]^.reg := ThisReg;
taicpu(hp1).opsize := TargetSize;
end;
end
else
else if (TargetSize = S_B) and (MaxSize = S_W) and (taicpu(hp1).opsize = S_WL) then
begin
DebugMsg(SPeepholeOptimization + 'Movzx2Mov 2', hp1);
taicpu(hp1).opcode := A_MOV;
{ Need to change the size of the output }
DebugMsg(SPeepholeOptimization + 'movzwl2movzbl 2', hp1);
taicpu(hp1).oper[0]^.reg := ThisReg;
taicpu(hp1).opsize := TargetSize;
taicpu(hp1).opsize := S_BL;
end;
end
else if (TargetSize = S_B) and (MaxSize = S_W) and (taicpu(hp1).opsize = S_WL) then
begin
{ Need to change the size of the output }
DebugMsg(SPeepholeOptimization + 'movzwl2movzbl 2', hp1);
taicpu(hp1).oper[0]^.reg := ThisReg;
taicpu(hp1).opsize := S_BL;
end;
end;
@ -8643,6 +8693,7 @@ unit aoptx86;
{ Update the register to its new size }
setsubreg(ThisReg, TargetSubReg);
RegInUse := False;
if not SuperRegistersEqual(taicpu(hp1).oper[1]^.reg, ThisReg) then
begin
@ -8650,7 +8701,6 @@ unit aoptx86;
{ Check to see if the active register is used afterwards;
if not, we can change it and make a saving. }
RegInUse := False;
TransferUsedRegs(TmpUsedRegs);
{ The target register may be marked as in use to cross
@ -8723,6 +8773,8 @@ unit aoptx86;
else
RemoveInstruction(hp1);
hp1_removed := True;
{ Instruction will become "mov %reg,%reg" }
if not p_removed and (taicpu(p).opcode = A_MOV) and
MatchOperand(taicpu(p).oper[0]^, ThisReg) then
@ -8764,7 +8816,7 @@ unit aoptx86;
else
AdjustFinalLoad;
Result := AdjustInitialLoad or Result;
Result := AdjustInitialLoadAndSize or Result;
{ Now go through every instruction we found and change the
size. If TargetSize = MaxSize, then almost no changes are
@ -8799,6 +8851,7 @@ unit aoptx86;
begin
Result := False;
p_removed := False;
hp1_removed := False;
ThisReg := taicpu(p).oper[1]^.reg;
{ Check for:
@ -9057,7 +9110,7 @@ unit aoptx86;
if LowerUnsignedOverflow and not UpperUnsignedOverflow then
begin
{ Exceeded lower bound but not upper bound }
TargetSize := MaxSize;
Exit;
end
else if not LowerSignedOverflow or not LowerUnsignedOverflow then
begin
@ -9078,8 +9131,8 @@ unit aoptx86;
InternalError(2021051002);
end;
if TargetSize <> MaxSize then
begin
if TargetSize <> MaxSize then
begin
{ Update the register to its new size }
setsubreg(ThisReg, TargetSubReg);
@ -9088,7 +9141,7 @@ unit aoptx86;
taicpu(hp1).opsize := TargetSize;
{ Convert the input MOVZX to a MOV if necessary }
AdjustInitialLoad;
AdjustInitialLoadAndSize;
if (InstrMax >= 0) then
begin