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* patch by J. Gareth Moreton: CMP chain shortcutting, resolves #39141

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git-svn-id: trunk@49592 -
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florian 2021-07-10 20:29:00 +00:00
parent d7b509e149
commit d16160be91
1 changed files with 147 additions and 8 deletions
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155
compiler/x86/aoptx86.pas
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@ -4789,23 +4789,165 @@ unit aoptx86;
end;
function IsCmpSubset(cond1, cond2: TAsmCond): Boolean; inline;
begin
Result := condition_in(cond1, cond2) or
{ Not strictly subsets due to the actual flags checked, but because we're
comparing integers, E is a subset of AE and GE and their aliases }
((cond1 in [C_E, C_Z]) and (cond2 in [C_AE, C_NB, C_NC, C_GE, C_NL]));
end;
function TX86AsmOptimizer.OptPass1Cmp(var p: tai): boolean;
var
v: TCGInt;
hp1, hp2: tai;
hp1, hp2, p_dist, p_jump, hp1_dist, p_label, hp1_label: tai;
FirstMatch: Boolean;
JumpLabel, JumpLabel_dist, JumpLabel_far: TAsmLabel;
begin
Result:=false;
{ All these optimisations need a next instruction }
if not GetNextInstruction(p, hp1) then
Exit;
{ Search for:
cmp ###,###
j(c1) @lbl1
...
@lbl:
cmp ###.### (same comparison as above)
j(c2) @lbl2
If c1 is a subset of c2, change to:
cmp ###,###
j(c2) @lbl2
(@lbl1 may become a dead label as a result)
}
{ Also handle cases where there are multiple jumps in a row }
p_jump := hp1;
while Assigned(p_jump) and MatchInstruction(p_jump, A_JCC, []) do
begin
if IsJumpToLabel(taicpu(p_jump)) then
begin
JumpLabel := TAsmLabel(taicpu(p_jump).oper[0]^.ref^.symbol);
p_label := nil;
if Assigned(JumpLabel) then
p_label := getlabelwithsym(JumpLabel);
if Assigned(p_label) and
GetNextInstruction(p_label, p_dist) and
MatchInstruction(p_dist, A_CMP, []) and
MatchOperand(taicpu(p_dist).oper[0]^, taicpu(p).oper[0]^) and
MatchOperand(taicpu(p_dist).oper[1]^, taicpu(p).oper[1]^) and
GetNextInstruction(p_dist, hp1_dist) and
MatchInstruction(hp1_dist, A_JCC, []) then { This doesn't have to be an explicit label }
begin
JumpLabel_dist := TAsmLabel(taicpu(hp1_dist).oper[0]^.ref^.symbol);
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 IsCmpSubset(taicpu(p_jump).condition, taicpu(hp1_dist).condition) then
begin
{ Any registers used here will already be allocated }
if Assigned(JumpLabel_dist) then
JumpLabel_dist.IncRefs;
if Assigned(JumpLabel) then
JumpLabel.DecRefs;
DebugMsg(SPeepholeOptimization + 'CMP/Jcc/@Lbl/CMP/Jcc -> CMP/Jcc, redirecting first jump', p_jump);
taicpu(p_jump).condition := taicpu(hp1_dist).condition;
taicpu(p_jump).loadref(0, taicpu(hp1_dist).oper[0]^.ref^);
Result := True;
{ Don't exit yet. Since p and p_jump haven't actually been
removed, we can check for more on this iteration }
end
else if IsCmpSubset(taicpu(hp1_dist).condition, inverse_cond(taicpu(p_jump).condition)) and
GetNextInstruction(hp1_dist, hp1_label) and
SkipAligns(hp1_label, hp1_label) and
(hp1_label.typ = ait_label) then
begin
JumpLabel_far := tai_label(hp1_label).labsym;
if (JumpLabel_far = JumpLabel_dist) or (JumpLabel_far = JumpLabel) then
{ This is an infinite loop }
Exit;
if Assigned(JumpLabel_far) then
begin
{ In this situation, if the first jump branches, the second one will never,
branch so change the destination label to after the second jump }
DebugMsg(SPeepholeOptimization + 'CMP/Jcc/@Lbl/CMP/Jcc/@Lbl -> CMP/Jcc, redirecting first jump to 2nd label', p_jump);
if Assigned(JumpLabel) then
JumpLabel.DecRefs;
JumpLabel_far.IncRefs;
taicpu(p_jump).oper[0]^.ref^.symbol := JumpLabel_far;
Result := True;
{ Don't exit yet. Since p and p_jump haven't actually been
removed, we can check for more on this iteration }
Continue;
end;
end;
end;
end;
{ Search for:
cmp ###,###
j(c1) @lbl1
cmp ###,### (same as first)
Remove second cmp
}
if GetNextInstruction(p_jump, hp2) and
(
(
MatchInstruction(hp2, A_CMP, []) and
(
(
MatchOpType(taicpu(p), top_const, top_reg) and
(taicpu(hp2).oper[0]^.val = taicpu(p).oper[0]^.val) and
SuperRegistersEqual(taicpu(p).oper[1]^.reg, taicpu(hp2).oper[1]^.reg)
) or (
MatchOperand(taicpu(hp2).oper[0]^, taicpu(p).oper[0]^) and
MatchOperand(taicpu(hp2).oper[1]^, taicpu(p).oper[1]^)
)
)
) or (
{ Also match cmp $0,%reg; jcc @lbl; test %reg,%reg }
MatchOperand(taicpu(p).oper[0]^, 0) and
(taicpu(p).oper[1]^.typ = top_reg) and
MatchInstruction(hp2, A_TEST, []) and
MatchOpType(taicpu(hp2), top_reg, top_reg) and
(taicpu(hp2).oper[0]^.reg = taicpu(hp2).oper[1]^.reg) and
SuperRegistersEqual(taicpu(p).oper[1]^.reg, taicpu(hp2).oper[1]^.reg)
)
) then
begin
DebugMsg(SPeepholeOptimization + 'CMP/Jcc/CMP; removed superfluous CMP', hp2);
RemoveInstruction(hp2);
Result := True;
{ Continue the while loop in case "Jcc/CMP" follows the second CMP that was just removed }
end;
GetNextInstruction(p_jump, p_jump);
end;
if taicpu(p).oper[0]^.typ = top_const then
begin
{ Though GetNextInstruction can be factored out, it is an expensive
call, so delay calling it until we have first checked cheaper
conditions that are independent of it. }
if (taicpu(p).oper[0]^.val = 0) and
(taicpu(p).oper[1]^.typ = top_reg) and
GetNextInstruction(p, hp1) and
MatchInstruction(hp1,A_Jcc,A_SETcc,[]) then
begin
hp2 := p;
@ -4908,7 +5050,6 @@ unit aoptx86;
Exit;
end
else if (taicpu(p).oper[0]^.val = 1) and
GetNextInstruction(p, hp1) and
MatchInstruction(hp1,A_Jcc,A_SETcc,[]) and
(taicpu(hp1).condition in [C_L, C_NGE]) then
begin
@ -4955,7 +5096,6 @@ unit aoptx86;
end;
if (taicpu(p).oper[0]^.val=v) and
GetNextInstruction(p, hp1) and
MatchInstruction(hp1,A_Jcc,A_SETcc,[]) and
(Taicpu(hp1).condition in [C_E,C_NE]) then
begin
@ -4980,7 +5120,6 @@ unit aoptx86;
end;
if (taicpu(p).oper[1]^.typ = top_reg) and
GetNextInstruction(p, hp1) and
MatchInstruction(hp1,A_MOV,[]) and
not RegInInstruction(taicpu(p).oper[1]^.reg, hp1) and
(