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* x86: Fixed inefficiencies revealed in "TEST/JNE/TEST/JNE"

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optimisations after SkipAligns cull.

         A variant "TEST/JNE/TEST/JE/@Lbl" optimisation now exists to
	 accommodate for an intermediate jump optimisation that prevents
	 the original optimisation from working if performed first.
This commit is contained in:
J. Gareth "Curious Kit" Moreton 2023-11-29 08:02:43 +00:00 committed by FPK
parent 248082347f
commit ccf631eabd
1 changed files with 145 additions and 74 deletions
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219
compiler/x86/aoptx86.pas
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@ -5279,7 +5279,35 @@ unit aoptx86;
hp1, p_label, p_dist, hp1_dist, hp1_last: tai;
JumpLabel, JumpLabel_dist: TAsmLabel;
FirstValue, SecondValue: TCGInt;
TempBool: Boolean;
function OptimizeJump(var InputP: tai): Boolean;
var
TempBool: Boolean;
begin
Result := False;
TempBool := True;
if DoJumpOptimizations(InputP, TempBool) or
not TempBool then
begin
Result := True;
if Assigned(InputP) then
begin
{ CollapseZeroDistJump will be set to the label or an align
before it after the jump if it optimises, whether or not
the label is live or dead }
if (InputP.typ = ait_align) or
(
(InputP.typ = ait_label) and
not (tai_label(InputP).labsym.is_used)
) then
GetNextInstruction(InputP, InputP);
end;
Exit;
end;
end;
begin
Result := False;
if (taicpu(p).oper[0]^.typ = top_const) and
@ -5325,23 +5353,25 @@ unit aoptx86;
Exit;
end;
p_label := nil;
JumpLabel := nil;
if MatchInstruction(hp1, A_Jcc, []) then
begin
TempBool := True;
if DoJumpOptimizations(hp1, TempBool) or
not TempBool then
if OptimizeJump(hp1) then
begin
Result := True;
if Assigned(hp1) then
begin
if (hp1.typ in [ait_align]) then
SkipAligns(hp1, hp1);
{ CollapseZeroDistJump will be set to the label after the
jump if it optimises, whether or not it's live or dead }
if (hp1.typ in [ait_label]) and
not (tai_label(hp1).labsym.is_used) then
{ CollapseZeroDistJump will be set to the label or an align
before it after the jump if it optimises, whether or not
the label is live or dead }
if (hp1.typ = ait_align) or
(
(hp1.typ = ait_label) and
not (tai_label(hp1).labsym.is_used)
) then
GetNextInstruction(hp1, hp1);
end;
@ -5361,6 +5391,13 @@ unit aoptx86;
Exit;
end;
if IsJumpToLabel(taicpu(hp1)) then
begin
JumpLabel := TAsmLabel(taicpu(hp1).oper[0]^.ref^.symbol);
if Assigned(JumpLabel) then
p_label := getlabelwithsym(JumpLabel);
end;
end;
{ Search for:
@ -5440,6 +5477,12 @@ unit aoptx86;
GetNextInstruction(p_dist, hp1_dist) and
MatchInstruction(hp1_dist, A_JCC, []) then
begin
if OptimizeJump(hp1_dist) then
begin
Result := True;
Exit;
end;
if
(taicpu(p_dist).opcode = A_CMP) { constant will be zero } or
(
@ -5455,9 +5498,6 @@ unit aoptx86;
in case the flags are modified in between) }
if (FirstValue = SecondValue) then
begin
{ We have to check the entire range }
TempBool := not RegModifiedBetween(NR_DEFAULTFLAGS, hp1, p_dist);
if condition_in(taicpu(hp1_dist).condition, taicpu(hp1).condition) then
begin
{ Since the second jump's condition is a subset of the first, we
@ -5497,7 +5537,7 @@ unit aoptx86;
{ If a jump wasn't removed or made unconditional, only
remove the identical TEST instruction if the flags
weren't modified }
TempBool then
not RegModifiedBetween(NR_DEFAULTFLAGS, hp1, p_dist) then
begin
DebugMsg(SPeepholeOptimization + 'TEST/Jcc/TEST; removed superfluous TEST', p_dist);
RemoveInstruction(p_dist);
@ -5524,16 +5564,8 @@ unit aoptx86;
end;
end;
hp1_last := nil;
if (taicpu(hp1).condition in [C_NE, C_NZ]) and
(taicpu(hp1_dist).condition in [C_NE, C_NZ]) and
{ If the first instruction is test %reg,%reg or test $-1,%reg,
then the second jump will never branch, so it can also be
removed regardless of where it goes }
(
(FirstValue = -1) or
(SecondValue = -1) or
MatchOperand(taicpu(hp1_dist).oper[0]^, taicpu(hp1).oper[0]^)
) and
(
{ In this situation, the TEST/JNE pairs must be adjacent (fixes #40366) }
@ -5543,6 +5575,36 @@ unit aoptx86;
GetNextInstruction(hp1, hp1_last) and
(hp1_last = p_dist)
)
) and
(
(
{ Test the following variant:
test $x,(reg/ref)
jne @lbl1
test $y,(reg/ref)
je @lbl2
@lbl1:
Becomes:
test $(x or y),(reg/ref)
je @lbl2
@lbl1: (may become a dead label)
}
(taicpu(hp1_dist).condition in [C_E, C_Z]) and
GetNextInstruction(hp1_dist, hp1_last) and
(hp1_last = p_label)
) or
(
(taicpu(hp1_dist).condition in [C_NE, C_NZ]) and
{ If the first instruction is test %reg,%reg or test $-1,%reg,
then the second jump will never branch, so it can also be
removed regardless of where it goes }
(
(FirstValue = -1) or
(SecondValue = -1) or
MatchOperand(taicpu(hp1_dist).oper[0]^, taicpu(hp1).oper[0]^)
)
)
) then
begin
{ Same jump location... can be a register since nothing's changed }
@ -5551,31 +5613,48 @@ unit aoptx86;
merged $(x or y) is also test %reg,%reg / test $-1,%reg }
taicpu(p).loadconst(0, FirstValue or SecondValue);
if IsJumpToLabel(taicpu(hp1_dist)) then
TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol).DecRefs;
{ Only remove the second test if no jumps or other conditional instructions follow }
TransferUsedRegs(TmpUsedRegs);
UpdateUsedRegs(TmpUsedRegs, tai(p.Next));
UpdateUsedRegs(TmpUsedRegs, tai(hp1.Next));
UpdateUsedRegs(TmpUsedRegs, tai(p_dist.Next));
if not RegUsedAfterInstruction(NR_DEFAULTFLAGS, hp1_dist, TmpUsedRegs) then
if (hp1_last = p_label) then
begin
DebugMsg(SPeepholeOptimization + 'TEST/JNE/TEST/JNE merged', p);
{ Variant }
DebugMsg(SPeepholeOptimization + 'TEST/JNE/TEST/JE/@Lbl merged', p);
RemoveInstruction(p_dist);
{ Remove the first jump, not the second, to keep
any register deallocations between the second
TEST/JNE pair in the same place. Aids future
optimisation. }
if Assigned(JumpLabel) then
JumpLabel.decrefs;
RemoveInstruction(hp1);
end
else
begin
DebugMsg(SPeepholeOptimization + 'TEST/JNE/TEST/JNE merged (second TEST preserved)', p);
{ Only remove the second test if no jumps or other conditional instructions follow }
TransferUsedRegs(TmpUsedRegs);
UpdateUsedRegs(TmpUsedRegs, tai(p.Next));
UpdateUsedRegs(TmpUsedRegs, tai(hp1.Next));
UpdateUsedRegs(TmpUsedRegs, tai(p_dist.Next));
if not RegUsedAfterInstruction(NR_DEFAULTFLAGS, hp1_dist, TmpUsedRegs) then
begin
DebugMsg(SPeepholeOptimization + 'TEST/JNE/TEST/JNE merged', p);
RemoveInstruction(p_dist);
{ Remove second jump in this instance }
RemoveInstruction(hp1_dist);
{ Remove the first jump, not the second, to keep
any register deallocations between the second
TEST/JNE pair in the same place. Aids future
optimisation. }
if Assigned(JumpLabel) then
JumpLabel.decrefs;
RemoveInstruction(hp1);
end
else
begin
DebugMsg(SPeepholeOptimization + 'TEST/JNE/TEST/JNE merged (second TEST preserved)', p);
if IsJumpToLabel(taicpu(hp1_dist)) then
TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol).DecRefs;
{ Remove second jump in this instance }
RemoveInstruction(hp1_dist);
end;
end;
Result := True;
@ -5614,43 +5693,35 @@ unit aoptx86;
if (taicpu(p).oper[1]^.typ = top_reg) and
(taicpu(p).oper[0]^.typ = top_reg) and
(taicpu(p).oper[0]^.reg = taicpu(p).oper[1]^.reg) and
MatchInstruction(hp1, A_JCC, []) and
IsJumpToLabel(taicpu(hp1)) then
{ p_label <> nil is a marker that hp1 is a Jcc to a label }
Assigned(p_label) and
GetNextInstruction(p_label, p_dist) and
MatchInstruction(p_dist, A_TEST, []) and
{ It's fine if the second test uses smaller sub-registers }
(taicpu(p_dist).opsize <= taicpu(p).opsize) and
MatchOpType(taicpu(p_dist), top_reg, top_reg) and
SuperRegistersEqual(taicpu(p_dist).oper[0]^.reg, taicpu(p).oper[0]^.reg) and
SuperRegistersEqual(taicpu(p_dist).oper[1]^.reg, taicpu(p).oper[1]^.reg) and
GetNextInstruction(p_dist, hp1_dist) and
MatchInstruction(hp1_dist, A_JCC, []) then { This doesn't have to be an explicit label }
begin
JumpLabel := TAsmLabel(taicpu(hp1).oper[0]^.ref^.symbol);
p_label := nil;
if Assigned(JumpLabel) then
p_label := getlabelwithsym(JumpLabel);
JumpLabel_dist := TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol);
if Assigned(p_label) and
GetNextInstruction(p_label, p_dist) and
MatchInstruction(p_dist, A_TEST, []) and
{ It's fine if the second test uses smaller sub-registers }
(taicpu(p_dist).opsize <= taicpu(p).opsize) and
MatchOpType(taicpu(p_dist), top_reg, top_reg) and
SuperRegistersEqual(taicpu(p_dist).oper[0]^.reg, taicpu(p).oper[0]^.reg) and
SuperRegistersEqual(taicpu(p_dist).oper[1]^.reg, taicpu(p).oper[1]^.reg) and
GetNextInstruction(p_dist, hp1_dist) and
MatchInstruction(hp1_dist, A_JCC, []) then { This doesn't have to be an explicit label }
if JumpLabel = JumpLabel_dist then
{ This is an infinite loop }
Exit;
{ Best optimisation when the first condition is a subset (or equal) of the second }
if condition_in(taicpu(hp1).condition, taicpu(hp1_dist).condition) then
begin
JumpLabel_dist := TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol);
{ Any registers used here will already be allocated }
if Assigned(JumpLabel) then
JumpLabel.DecRefs;
if JumpLabel = JumpLabel_dist then
{ This is an infinite loop }
Exit;
{ Best optimisation when the first condition is a subset (or equal) of the second }
if condition_in(taicpu(hp1).condition, taicpu(hp1_dist).condition) then
begin
{ Any registers used here will already be allocated }
if Assigned(JumpLabel) then
JumpLabel.DecRefs;
DebugMsg(SPeepholeOptimization + 'TEST/Jcc/@Lbl/TEST/Jcc -> TEST/Jcc, redirecting first jump', hp1);
taicpu(hp1).loadref(0, taicpu(hp1_dist).oper[0]^.ref^); { This also increases the reference count }
Result := True;
Exit;
end;
DebugMsg(SPeepholeOptimization + 'TEST/Jcc/@Lbl/TEST/Jcc -> TEST/Jcc, redirecting first jump', hp1);
taicpu(hp1).loadref(0, taicpu(hp1_dist).oper[0]^.ref^); { This also increases the reference count }
Result := True;
Exit;
end;
end;
end;