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Bolder OptPass2Movx optimisations, including a simplification fix

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J. Gareth "Curious Kit" Moreton 2021-12-04 06:49:00 +00:00 committed by FPK
parent da899df6b2
commit f02b7508de
1 changed files with 84 additions and 27 deletions
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111
compiler/x86/aoptx86.pas
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@ -7954,7 +7954,7 @@ unit aoptx86;
{ Data flow analysis }
TestValMin, TestValMax: TCgInt;
SmallerOverflow: Boolean;
SmallerOverflow, BitwiseOnly, OrXorUsed: Boolean;
begin
Result := False;
@ -8000,6 +8000,8 @@ unit aoptx86;
TrySmaller := S_NO;
SmallerOverflow := False;
RegChanged := False;
BitwiseOnly := True;
OrXorUsed := False;
hp1 := p;
@ -8118,9 +8120,7 @@ unit aoptx86;
end;
end;
{ OR and XOR are not included because they can too easily fool
the data flow analysis (they can cause non-linear behaviour) }
A_ADD,A_SUB,A_AND,A_SHL,A_SHR:
A_ADD,A_SUB,A_AND,A_OR,A_XOR,A_SHL,A_SHR:
begin
if
(taicpu(hp1).oper[1]^.typ <> top_reg) or
@ -8153,29 +8153,49 @@ unit aoptx86;
) then
Break;
{ Only process OR and XOR if there are only bitwise operations,
since otherwise they can too easily fool the data flow
analysis (they can cause non-linear behaviour) }
case taicpu(hp1).opcode of
A_ADD:
if (taicpu(hp1).oper[0]^.typ = top_reg) then
begin
TestValMin := TestValMin * 2;
TestValMax := TestValMax * 2;
end
else
begin
TestValMin := TestValMin + taicpu(hp1).oper[0]^.val;
TestValMax := TestValMax + taicpu(hp1).oper[0]^.val;
end;
begin
if OrXorUsed then
{ Too high a risk of non-linear behaviour that breaks DFA here }
Break
else
BitwiseOnly := False;
if (taicpu(hp1).oper[0]^.typ = top_reg) then
begin
TestValMin := TestValMin * 2;
TestValMax := TestValMax * 2;
end
else
begin
TestValMin := TestValMin + taicpu(hp1).oper[0]^.val;
TestValMax := TestValMax + taicpu(hp1).oper[0]^.val;
end;
end;
A_SUB:
if (taicpu(hp1).oper[0]^.typ = top_reg) then
begin
TestValMin := 0;
TestValMax := 0;
end
else
begin
TestValMin := TestValMin - taicpu(hp1).oper[0]^.val;
TestValMax := TestValMax - taicpu(hp1).oper[0]^.val;
end;
begin
if OrXorUsed then
{ Too high a risk of non-linear behaviour that breaks DFA here }
Break
else
BitwiseOnly := False;
if (taicpu(hp1).oper[0]^.typ = top_reg) then
begin
TestValMin := 0;
TestValMax := 0;
end
else
begin
TestValMin := TestValMin - taicpu(hp1).oper[0]^.val;
TestValMax := TestValMax - taicpu(hp1).oper[0]^.val;
end;
end;
A_AND:
if (taicpu(hp1).oper[0]^.typ = top_const) then
begin
@ -8211,6 +8231,26 @@ unit aoptx86;
TestValMin := TestValMin and taicpu(hp1).oper[0]^.val;
TestValMax := TestValMax and taicpu(hp1).oper[0]^.val;
end;
A_OR:
begin
if not BitwiseOnly then
Break;
OrXorUsed := True;
TestValMin := TestValMin or taicpu(hp1).oper[0]^.val;
TestValMax := TestValMax or taicpu(hp1).oper[0]^.val;
end;
A_XOR:
begin
if not BitwiseOnly then
Break;
OrXorUsed := True;
TestValMin := TestValMin xor taicpu(hp1).oper[0]^.val;
TestValMax := TestValMax xor taicpu(hp1).oper[0]^.val;
end;
A_SHL:
begin
TestValMin := TestValMin shl taicpu(hp1).oper[0]^.val;
@ -8469,8 +8509,6 @@ unit aoptx86;
hp2 := p;
repeat
UpdateUsedRegs(TmpUsedRegs, tai(hp2.next));
{ Explicitly check for the excluded register (don't include the first
instruction as it may be reading from here }
if ((p <> hp2) and (RegInInstruction(taicpu(hp1).oper[1]^.reg, hp2))) or
@ -8480,12 +8518,31 @@ unit aoptx86;
Break;
end;
UpdateUsedRegs(TmpUsedRegs, tai(hp2.next));
if not GetNextInstruction(hp2, hp2) then
InternalError(2020112340);
until (hp2 = hp1);
if not RegInUse and not RegUsedAfterInstruction(ThisReg, hp1, TmpUsedRegs) then
if not RegInUse and RegUsedAfterInstruction(ThisReg, hp1, TmpUsedRegs) then
begin
RegInUse := True;
{ We might still be able to get away with this }
if GetNextInstructionUsingReg(hp1, hp2, ThisReg) and
(hp2.typ = ait_instruction) and
(
{ Under -O1 and -O2, GetNextInstructionUsingReg may return an
instruction that doesn't actually contain ThisReg }
(cs_opt_level3 in current_settings.optimizerswitches) or
RegInInstruction(ThisReg, hp2)
) and
RegLoadedWithNewValue(ThisReg, hp2) then
RegInUse := False;
end;
if not RegInUse then
begin
DebugMsg(SPeepholeOptimization + 'Simplified register usage so ' + debug_regname(taicpu(hp1).oper[1]^.reg) + ' = ' + debug_regname(taicpu(p).oper[1]^.reg), p);
ThisReg := taicpu(hp1).oper[1]^.reg;