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New MOV optimisation that helps reduce instruction count and memory accesses

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J. Gareth "Curious Kit" Moreton 2022-01-09 08:38:21 +00:00 committed by FPK
parent 985e8d3d13
commit bb49c190af
1 changed files with 68 additions and 0 deletions
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68
compiler/x86/aoptx86.pas
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@ -3517,6 +3517,74 @@ unit aoptx86;
end;
{ mov x,reg1; mov y,reg1 -> mov y,reg1 is handled by the Mov2Nop 5 optimisation }
{ Change:
movl %reg1,%reg2
movl x(%reg1),%reg1 (If something other than %reg1 is written to, DeepMOVOpt would have caught it)
movl x(%reg2),%regX (%regX can be %reg2 or something else)
To:
movl %reg1,%reg2 (if %regX = %reg2, then remove this instruction)
movl x(%reg1),%reg1
movl %reg1,%regX
}
if MatchOpType(taicpu(p), top_reg, top_reg) then
begin
CurrentReg := taicpu(p).oper[0]^.reg;
ActiveReg := taicpu(p).oper[1]^.reg;
if (taicpu(hp1).oper[0]^.typ = top_ref) { The other operand will be a register } and
(taicpu(hp1).oper[1]^.reg = CurrentReg) and
RegInRef(CurrentReg, taicpu(hp1).oper[0]^.ref^) and
GetNextInstruction(hp1, hp2) and
MatchInstruction(hp2, A_MOV, [taicpu(p).opsize]) and
(taicpu(hp2).oper[0]^.typ = top_ref) { The other operand will be a register } then
begin
SourceRef := taicpu(hp2).oper[0]^.ref^;
if RegInRef(ActiveReg, SourceRef) and
{ If %reg1 also appears in the second reference, then it will
not refer to the same memory block as the first reference }
not RegInRef(CurrentReg, SourceRef) then
begin
{ Check to see if the references match if %reg2 is changed to %reg1 }
if SourceRef.base = ActiveReg then
SourceRef.base := CurrentReg;
if SourceRef.index = ActiveReg then
SourceRef.index := CurrentReg;
{ RefsEqual also checks to ensure both references are non-volatile }
if RefsEqual(taicpu(hp1).oper[0]^.ref^, SourceRef) then
begin
taicpu(hp2).loadreg(0, CurrentReg);
DebugMsg(SPeepholeOptimization + 'Optimised register duplication and memory read (MovMovMov2MovMovMov)', p);
Result := True;
if taicpu(hp2).oper[1]^.reg = ActiveReg then
begin
DebugMsg(SPeepholeOptimization + 'Mov2Nop 5a done', p);
RemoveCurrentP(p, hp1);
Exit;
end
else
begin
{ Check to see if %reg2 is no longer in use }
TransferUsedRegs(TmpUsedRegs);
UpdateUsedRegs(TmpUsedRegs, tai(p.Next));
UpdateUsedRegs(TmpUsedRegs, tai(hp1.Next));
if not RegUsedAfterInstruction(ActiveReg, hp2, TmpUsedRegs) then
begin
DebugMsg(SPeepholeOptimization + 'Mov2Nop 5b done', p);
RemoveCurrentP(p, hp1);
Exit;
end;
end;
{ If we reach this point, p and hp1 weren't actually modified,
so we can do a bit more work on this pass }
end;
end;
end;
end;
end;
{ search further than the next instruction for a mov (as long as it's not a jump) }