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@@ -128,7 +128,7 @@ unit aoptx86;
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{ Returns true if the given MOV instruction can be safely converted to CMOV }
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{ Returns true if the given MOV instruction can be safely converted to CMOV }
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- class function CanBeCMOV(p, cond_p: tai) : boolean; static;
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+ class function CanBeCMOV(p, cond_p: tai; var RefModified: Boolean) : boolean; static;
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{ Like UpdateUsedRegs, but ignores deallocations }
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{ Like UpdateUsedRegs, but ignores deallocations }
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class procedure UpdateIntRegsNoDealloc(var AUsedRegs: TAllUsedRegs; p: Tai); static;
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class procedure UpdateIntRegsNoDealloc(var AUsedRegs: TAllUsedRegs; p: Tai); static;
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@@ -11613,7 +11613,7 @@ unit aoptx86;
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end;
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end;
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- class function TX86AsmOptimizer.CanBeCMOV(p, cond_p: tai) : boolean;
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+ class function TX86AsmOptimizer.CanBeCMOV(p, cond_p: tai; var RefModified: Boolean) : boolean;
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begin
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begin
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Result := assigned(p) and
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Result := assigned(p) and
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MatchInstruction(p,A_MOV,[S_W,S_L,S_Q]) and
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MatchInstruction(p,A_MOV,[S_W,S_L,S_Q]) and
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@@ -11630,6 +11630,8 @@ unit aoptx86;
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(
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(
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IsRefSafe(taicpu(p).oper[0]^.ref) or
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IsRefSafe(taicpu(p).oper[0]^.ref) or
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(
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(
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+ { Don't use the reference in the condition if one of its registers got modified by a previous MOV }
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+ not RefModified and
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{ If the reference also appears in the condition, then we know it's safe, otherwise
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{ If the reference also appears in the condition, then we know it's safe, otherwise
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any kind of access violation would have occurred already }
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any kind of access violation would have occurred already }
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Assigned(cond_p) and
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Assigned(cond_p) and
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@@ -11699,6 +11701,7 @@ unit aoptx86;
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carryadd_opcode : TAsmOp;
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carryadd_opcode : TAsmOp;
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symbol: TAsmSymbol;
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symbol: TAsmSymbol;
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increg, tmpreg: TRegister;
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increg, tmpreg: TRegister;
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+ RefModified: Boolean;
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{$ifndef i8086}
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{$ifndef i8086}
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{ Code and variables specific to CMOV optimisations }
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{ Code and variables specific to CMOV optimisations }
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hp3,hp4,hp5,
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hp3,hp4,hp5,
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@@ -12241,6 +12244,7 @@ unit aoptx86;
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FillChar(ConstRegs[0], MAX_CMOV_REGISTERS * SizeOf(TRegister), 0);
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FillChar(ConstRegs[0], MAX_CMOV_REGISTERS * SizeOf(TRegister), 0);
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FillChar(ConstVals[0], MAX_CMOV_REGISTERS * SizeOf(TCGInt), 0);
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FillChar(ConstVals[0], MAX_CMOV_REGISTERS * SizeOf(TCGInt), 0);
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+ RefModified := False;
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while assigned(hp1) and
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while assigned(hp1) and
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{ Stop on the label we found }
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{ Stop on the label we found }
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(hp1 <> hp_lblxxx) do
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(hp1 <> hp_lblxxx) do
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@@ -12249,8 +12253,38 @@ unit aoptx86;
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ait_instruction:
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ait_instruction:
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if MatchInstruction(hp1, A_MOV, [S_W, S_L{$ifdef x86_64}, S_Q{$endif x86_64}]) then
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if MatchInstruction(hp1, A_MOV, [S_W, S_L{$ifdef x86_64}, S_Q{$endif x86_64}]) then
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begin
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begin
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- if CanBeCMOV(hp1, hp_prev) then
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- Inc(l)
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+ if CanBeCMOV(hp1, hp_prev, RefModified) then
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+ begin
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+ Inc(l);
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+
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+ { MOV instruction will be writing to a register }
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+ if Assigned(hp_prev) and
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+ { Make sure the sizes match too so we're reading and writing the same number of bytes }
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+ (hp_prev.typ = ait_instruction) and
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+ (taicpu(hp_prev).ops = 2) and
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+ (
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+ (
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+ (taicpu(hp_prev).oper[0]^.typ = top_ref) and
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+ RegInRef(taicpu(hp1).oper[1]^.reg, taicpu(hp_prev).oper[0]^.ref^)
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+ ) or
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+ (
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+ (taicpu(hp_prev).oper[1]^.typ = top_ref) and
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+ RegInRef(taicpu(hp1).oper[1]^.reg, taicpu(hp_prev).oper[1]^.ref^)
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+ )
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+ ) then
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+ { It is no longer safe to use the reference in the condition.
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+ this prevents problems such as:
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+ mov (%reg),%reg
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+ mov (%reg),...
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+
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+ When the comparison is cmp (%reg),0 and guarding against a null pointer deallocation
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+ (fixes #40165)
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+
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+ Note: "mov (%reg1),%reg2; mov (%reg2),..." won't be optimised this way since
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+ at least one of (%reg1) and (%reg2) won't be in the condition and is hence unsafe.
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+ }
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+ RefModified := True;
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+ end
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else if not (cs_opt_size in current_settings.optimizerswitches) and
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else if not (cs_opt_size in current_settings.optimizerswitches) and
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{ CMOV with constants grows the code size }
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{ CMOV with constants grows the code size }
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TryCMOVConst(hp1, hp_prev, hp_stop, c, l) then
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TryCMOVConst(hp1, hp_prev, hp_stop, c, l) then
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@@ -12445,6 +12479,7 @@ unit aoptx86;
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end;
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end;
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{ Analyse the second batch of MOVs to see if the setup is valid }
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{ Analyse the second batch of MOVs to see if the setup is valid }
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+ RefModified := False;
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hp1 := hpmov2;
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hp1 := hpmov2;
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while assigned(hp1) and
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while assigned(hp1) and
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(hp1 <> hp_lblyyy) do
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(hp1 <> hp_lblyyy) do
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@@ -12453,8 +12488,38 @@ unit aoptx86;
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ait_instruction:
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ait_instruction:
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if MatchInstruction(hp1, A_MOV, [S_W, S_L{$ifdef x86_64}, S_Q{$endif x86_64}]) then
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if MatchInstruction(hp1, A_MOV, [S_W, S_L{$ifdef x86_64}, S_Q{$endif x86_64}]) then
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begin
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begin
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- if CanBeCMOV(hp1, hp_prev) then
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- Inc(l)
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+ if CanBeCMOV(hp1, hp_prev, RefModified) then
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+ begin
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+ Inc(l);
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+
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+ { MOV instruction will be writing to a register }
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+ if Assigned(hp_prev) and
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+ { Make sure the sizes match too so we're reading and writing the same number of bytes }
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+ (hp_prev.typ = ait_instruction) and
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+ (taicpu(hp_prev).ops = 2) and
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+ (
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+ (
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+ (taicpu(hp_prev).oper[0]^.typ = top_ref) and
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+ RegInRef(taicpu(hp1).oper[1]^.reg, taicpu(hp_prev).oper[0]^.ref^)
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+ ) or
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+ (
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+ (taicpu(hp_prev).oper[1]^.typ = top_ref) and
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+ RegInRef(taicpu(hp1).oper[1]^.reg, taicpu(hp_prev).oper[1]^.ref^)
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+ )
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+ ) then
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+ { It is no longer safe to use the reference in the condition.
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+ this prevents problems such as:
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+ mov (%reg),%reg
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+ mov (%reg),...
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+
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+ When the comparison is cmp (%reg),0 and guarding against a null pointer deallocation
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+ (fixes #40165)
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+
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+ Note: "mov (%reg1),%reg2; mov (%reg2),..." won't be optimised this way since
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+ at least one of (%reg1) and (%reg2) won't be in the condition and is hence unsafe.
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+ }
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+ RefModified := True;
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+ end
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else if not (cs_opt_size in current_settings.optimizerswitches)
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else if not (cs_opt_size in current_settings.optimizerswitches)
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{ CMOV with constants grows the code size }
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{ CMOV with constants grows the code size }
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and TryCMOVConst(hp1, hpmov2, hp_lblyyy, c, l) then
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and TryCMOVConst(hp1, hpmov2, hp_lblyyy, c, l) then
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J. Gareth "Curious Kit" Moreton