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* patch by J. Gareth Moreton: SubMov2LeaSub optimisation improvement, resolves #38555

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git-svn-id: trunk@48871 -
This commit is contained in:
florian 2021-03-02 21:27:43 +00:00
parent 187d63c8e1
commit 01937c4630
1 changed files with 20 additions and 6 deletions
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26
compiler/x86/aoptx86.pas
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@ -7125,7 +7125,7 @@ unit aoptx86;
movl/q %reg1,%reg2
To:
leal/q $-x(%reg1),%reg2
subl/q $x,%reg1
subl/q $x,%reg1 (can be removed if %reg1 or the flags are not used afterwards)
Breaks the dependency chain and potentially permits the removal of
a CMP instruction if one follows.
@ -7149,12 +7149,26 @@ unit aoptx86;
taicpu(hp1).opcode := A_LEA;
taicpu(hp1).loadref(0, NewRef);
{ Move what is now the LEA instruction to before the SUB instruction }
Asml.Remove(hp1);
Asml.InsertBefore(hp1, p);
AllocRegBetween(taicpu(hp1).oper[1]^.reg, hp1, p, UsedRegs);
TransferUsedRegs(TmpUsedRegs);
UpdateUsedRegs(TmpUsedRegs, tai(p.Next));
if RegUsedAfterInstruction(NewRef.base, hp1, TmpUsedRegs) or
RegUsedAfterInstruction(NR_DEFAULTFLAGS, hp1, TmpUsedRegs) then
begin
{ Move what is now the LEA instruction to before the SUB instruction }
Asml.Remove(hp1);
Asml.InsertBefore(hp1, p);
AllocRegBetween(taicpu(hp1).oper[1]^.reg, hp1, p, UsedRegs);
DebugMsg(SPeepholeOptimization + 'SubMov2LeaSub', p);
p := hp1;
end
else
begin
{ Since %reg1 or the flags aren't used afterwards, we can delete p completely }
RemoveCurrentP(p, hp1);
DebugMsg(SPeepholeOptimization + 'SubMov2Lea', p);
end;
DebugMsg(SPeepholeOptimization + 'SubMov2LeaSub', p);
Result := True;
end;
end;